Class 8

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3

Haryana State Board HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3

प्रश्न 1.
क्या किसी बहुफलक के फलक नीचे दिए अनुसार हो सकते हैं?
(i) 3 त्रिभुज
(ii) 4 त्रिभुज
(iii) एक वर्ग और चार त्रिभुज।
हल:
(i) 3 त्रिभुज – नहीं।
(ii) 4 त्रिभुज – हाँ।
(iii) एक वर्ग और चार त्रिभुज – हाँ।

प्रश्न 2.
क्या ऐसा बहुफलक सम्भव है जिसके फलकों की संख्या कोई भी संख्या हो?
हल:
हाँ, सम्भव है केवल तभी जब फलकों की संख्या कम-से-कम 4 या 4 से अधिक हो ।

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3

प्रश्न 3.
निम्नलिखित (पा.पु. पृष्ठ 176) में से कौन-कौन प्रिज्म है?
हल :
बिना छिली हुई पेंसिल तथा बॉक्स प्रिज्म हैं।

प्रश्न 4.
(i) प्रिज्म तथा बेलन किस प्रकार एक जैसे हैं ?
(ii) पिरामिड और शंकु किस प्रकार एक जैसे हैं ?
हल :
(i) प्रिज्म, बेलन का रूप तब ले लेता है, जब आधार की भुजाओं की संख्या बड़ी और बड़ी होती जाती है।
(ii) एक पिरामिड, जब शंकु का रूप ले लेता है, तब आधार की भुजाओं की संख्या बड़ी और बड़ी हो जाती है।

प्रश्न 5.
क्या एक वर्ग प्रिज्म और एक घन एक ही होते है ? स्पष्ट कीजिए।
हल :
नहीं, एक वर्ग प्रिज्म और एक घन एक ही नहीं होते हैं, एक घनाभ भी हो सकता है ।

प्रश्न 6.
इन ठोसों के लिए ऑयलर सूत्र का सत्यापन कीजिए
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3 -1
हल:
(i)
F = 6
E = 15
V = 10
ऑयलर सूत्र, F + V – E = 2 से
F + V – E = 7 + 10 – 15 = 17 – 15 = 2
इति सिद्धम्

(ii)
F = 9
E = 16
V = 9
F + V – E = 9 + 9 – 16 = 18 – 16 = 2
इति सिद्धम्

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3

प्रश्न 7.
ऑयलर सूत्र का प्रयोग करते हुए, अज्ञात संख्या को ज्ञात कीजिए-
Table 1
हल :
ऑयलर सूत्र, F + V – E = 2 से,
(i) F + V – E = 2
F + 6 – 12 = 2
F = 2 + 12 – 6
F = 14 – 6
F = 8

(ii) F + V – E = 2
5 + V – 9 = 2
V = 2 + 9 – 5
V = 11 – 5
V = 6

(iii) F + V – E = 2
20 + 12 – E = 2
20 + 12 – 2 = E
E = 32 – 2
E = 30

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3

प्रश्न 8.
क्या किसी बहुफलक के 10 फलक, 20 किनारे तथा 15 शीर्ष हो सकते हैं ?
हल :
F = 10, E = 20,V = 15
सूत्र, F + V – E = 2
L.H.S. = 10 + 15 – 20
= 25 – 20
= 5 = R.H.S.
हम जानते हैं कि, F + V – E = 2 होता है।
लेकिन हल करने पर F+V- E का मान 5 आ रहा इसलिए यह बहुफलक सम्भव नहीं है।

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.3 Read More »

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3

Haryana State Board HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Exercise 2.3

निम्न समीकरणों को हल कीजिये और अपने उत्तर की जाँच कीजिए।

प्रश्न 1.
3x = 2x + 18
हल :
3x = 2x + 18
2x को बाईं ओर पक्षांतरण करने पर 3x – 2x = 18
x= 18

जाँच-
3x= 2x + 18
L.H.S. में x= 18 रखने पर,
3x = 3 × 18 = 54

R.H.S. में x= 18 रखने पर,
2x + 18 = 2 × 18 + 18 = 54
=36+ 18
= 54
अत: L.H.S. = R.H.S.

प्रश्न 2.
5t – 3 = 3t – 5
हल :
5t – 3 = 3t – 5
3t तथा 3 का पक्षान्तरण करने पर,
5t – 3t = -5 + 3
या 2t = 2
या t = \(\frac{-2}{2}\) = -1
∴ t = -1

जाँच-
5t – 3= 3t – 5
L.H.S. में t = -1 रखने पर,
(5t – 3) = 5 (-1) – 3 = – 5 – 3 = -8.

R.H.S. में t=-1 रखने पर,
(3t – 5) = 3(-1) – 5 = – 3 – 5 = – 8
अत: L.H.S. = R.H.S.

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3

प्रश्न 3.
5x + 9 = 5 + 3x
हल :
5x +9 = 5 + 3x
3x तथा 9 का पक्षान्तरण करने पर,
5x – 3x = 5 – 9
या 2x = – 4
या x = \(\frac{-4}{2}\) = – 2
∴ x = – 2

जाँच-
5x + 9 = 5 + 3x
L.H.S. में x = – 2 रखने पर,
5(-2) + 9 = – 10 + 9 = – 1

L.H.S. में x = – 2 रखने पर,
5 + 3(-2) = 5 – 6 = – 1
अत: L.H.S. = R.H.S.

प्रश्न 4.
4z + 3 = 6 + 2z.
हल :
4z + 3 = 6 + 2z.
2z तथा 3 का पक्षान्तरण करने पर,
4z – 2z = 6 – 3
या 2z = 3
∴ z = \(\frac{3}{2}\)

जाँच-
4z + 3 = 6 + 2z.
L.H.S. में z = \(\frac{3}{2}\) रखने पर,
4z + 3 = z = \(4 \frac{3}{2}\) + 3 = 6 + 3 = 9

R.H.S. में z = \(\frac{3}{2}\) रखने पर,
6 + 4z = z = 6 + \(2 \frac{3}{2}\) = 6 + 3 = 9

∴ L.H.S. = R.H.S.

प्रश्न 5.
2x – 1 = 14 – x
हल :
2x – 1 = 14 – x
x तथा 1 का पक्षान्तरण करने पर,
2x + x = 14 + 1
या 3x = 15
या x = \(\frac{15}{3}\) = 5
∴ x = 5

जाँच-
2x – 1 = 14 – x
L.H.S. में x = 5 रखने पर,
2x – 1 = 2(5) – 1 = 10 – 1 = 9

R.H.S. में x = 5 रखने पर,
14 – x = 14 – 5 = 9

अत: L.H.S. = R.H.S.

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3

प्रश्न 6.
8x + 4 = 3 (x – 1) + 7
हल :
8x + 4 = 3 (x – 1) + 7
या 8x + 4 = 3x – 3 + 7
या 8x + 4 = 3x + 4
3x तथा 4 का पक्षान्तरण करने पर,
या
8x – 3x = 4 – 4
या 5x = 0
या x = \(\frac{0}{5}\) = 0
∴ x = 0

जाँच-
8x + 4 = 3 (x – 1) + 7

L.H.S. में x = 0 रखने पर,
8x + 4 = 8 × 0 + 4 = 0 + 4 = 4

R.H.S. में x = 0 रखने पर,
3 (x – 1) + 7 = 3(0 – 1) + 7 = 3 (-1) + 7 = 4

अत: L.H.S. = R.H.S.

प्रश्न 7.
x = \(\frac{4}{5}\)(x + 10)
हल :
x = \(\frac{4}{5}\)(x + 10)
कैंची गुणा करने पर,
5x = 4(x + 10)
या 5x = 4x + 40
4x का पक्षान्तरण करने पर,
5x – 4x = 40
∴ x = 40

जाँच-
x = \(\frac{4}{5}\)(x + 10)

L.H.S. में x = 40 रखने पर,
x = 40

R.H.S. में x = 40 रखने पर,
\(\frac{4}{5}\)(x + 10) = \(\frac{4}{5}\)(40 + 10)
= \(\frac{4}{5}\)(50) = \(\frac{4 × 50}{5}\) = 40

अत: L.H.S. = R.H.S.

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3

प्रश्न 8.
\(\frac{2x}{3}\) + 1 = \(\frac{7x}{15}\) + 3
हल :
\(\frac{2x}{3}\) + 1 = \(\frac{7x}{15}\) + 3
\(\frac{7x}{15}\) तथा 4 का पक्षान्तरण करने पर,
\(\frac{2x}{3}\) + \(\frac{7x}{15}\) = 3 – 1
या \(\frac{10x – 7x}{15}\) = 2
या \(\frac{3x}{15}\) = 2
कैंची गुणा करने पर-
3x = 2 × 15
या x = \(\frac{2 \times 15}{3}\) = 10
∴ x = 10

जाँच-
\(\frac{2x}{3}\) + 1 = \(\frac{7x}{15}\) + 3

L.H.S. में x = 10 रखने पर,
\(\frac{2x}{3}\) + 1 = \(\frac{2 \times 10}{3}\) + 3
= \(\frac{20}{3}\) + 1
= \(\frac{20 + 3}{3}\) = \(\frac{23}{3}\)

R.H.S. में x = 40 रखने पर,
\(\frac{7x}{15}\) + 3 = \(\frac{7 \times 10}{15}\) + 3
= \(\frac{14}{3}\) + 3
= \(\frac{14 + 9}{3}\) + 3 = \(\frac{23}{3}\) + 3

अत: L.H.S. = R.H.S.

प्रश्न 9.
2y + \(\frac{5}{3}\) = \(\frac{26}{3}\) – y.
हल :
y तथा \(\frac{5}{3}\) का पक्षान्तरण करने पर,

2y + y = \(\frac{26}{3}\) – \(\frac{5}{3}\)
या 3y = \(\frac{26 – 5}{3}\) = \(\frac{21}{3}\)
या 3y = 7
∴ y = \(\frac{7}{3}\)

जाँच-
2y + \(\frac{5}{3}\) = \(\frac{26}{3}\) – y.
L.H.S. में y = \(\frac{7}{3}\) रखने पर-
2y + \(\frac{5}{3}\) = \(2\left(\frac{7}{3}\right)+\frac{5}{3}\)
= \(\left(\frac{14}{3}\right)+\frac{5}{3}\)
= \(\frac{14 + 5}{3}\) = \(\frac{19}{3}\)

R.H.S. में y = \(\frac{7}{3}\) रखने पर-
\(\frac{26}{3}\) – y = \(\frac{26}{3}\) – \(\frac{7}{3}\)
= \(\frac{26 – 7}{3}\) = \(\frac{19}{3}\)

अत: L.H.S. = R.H.S.

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3

प्रश्न 10.
3m = 5m – \(\frac{8}{5}\)
हल :
3m = 5m – \(\frac{8}{5}\)
5m का पक्षान्तरण करने पर,
3m – 5m = – \(\frac{8}{5}\)
– 2m = – \(\frac{8}{5}\)
या m = \(\frac{8}{5 \times 2}=\frac{4}{5}\)
∴ m = \(\frac{4}{5}\)

जाँच-
3m = 5m – \(\frac{8}{5}\)

L.H.S. में m = \(\frac{4}{5}\) रखने पर-
3m = \(3 \frac{4}{5}\)
= \(\frac{12}{5}\)

R.H.S. में m = \(\frac{4}{5}\) रखने पर-
5m – \(\frac{8}{5}\) = \(5\left(\frac{4}{5}\right)-\frac{8}{5}\)
= \(4-\frac{8}{5}\)
= \(\frac{20 – 8}{5}\)
= \(\frac{12}{5}\)

अत: L.H.S. = R.H.S.

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3 Read More »

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1

Haryana State Board HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Exercise 2.1

निम्न समीकरणों को हल कीजिए-

प्रश्न 1.
x – 2 = 7
हल :
x – 2 = 7
2 को दायें पक्ष में पक्षांतरण करने पर,
x = 7 +2
∴ x = 9

प्रश्न 2.
y + 3 = 10
हल :
y + 3 = 10
3 को दायें पक्ष में पक्षांतरण करने पर,
y = 10 – 3
∴ y = 7

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1

प्रश्न 3.
6 = z + 2
हल :
6 = z + 2
2 को बायें पक्ष में पक्षांतरण करने पर,
6 – 2 = z
या 4 = z
∴ z = 4

प्रश्न 4.
\(\frac{3}{7}\) + x = \(\frac{17}{7}\)
हल :
\(\frac{3}{7}\) + x = \(\frac{17}{7}\)
\(\frac{3}{7}\) को दायें पक्ष में पक्षांतरण करने पर,
x = \(\frac{17}{7}\) – \(\frac{3}{7}\)
या x = \(\frac{14}{7}\) = 2
∴ x = 2

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1

प्रश्न 5.
6x = 12
हल :
6x = 12
या x = \(\frac{12}{6}\)
∴ x = 2

प्रश्न 6.
\(\frac{t}{5}\) = 10
हल :
\(\frac{t}{5}\) = 10
या t = 10 × 5 (कैंची गुणा करने)
∴ t = 50

प्रश्न 7.
\(\frac{2x}{3}\) = 18
हल :
\(\frac{2x}{3}\) = 18
या 2x = 18 × 3 (कैंची गुणा करने)
या x = \(\frac{18 \times 3}{2}\)
∴ x = 27

प्रश्न 8.
1.6 = \(\frac{y}{1.5}\)
हल :
1.6 = \(\frac{y}{1.5}\)
या \(\frac{16}{1}\) = \(\frac{y}{1.5}\)
या 1 × y = 1.6 × 1.5 (कैंची गुणा करने पर)
या y = 2.40
∴ y = 2.4

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1

प्रश्न 9.
7x – 9 = 16
हल :
7x – 9 = 16
– 9 को पांतरण करने पर,
7x = 16 + 9
या 7x = 25
∴ x = \(\frac{25}{7}\)

प्रश्न 10.
14y – 8 = 13
हल :
14y – 8 = 13
-8 को दायें पक्ष में पक्षांतरण करने पर,
14y = 13 +8
या 14y = 21
∴ y = \(\frac{21}{14}\) = \(\frac{3}{2}\)
∴ y = \(\frac{3}{2}\)

प्रश्न 11.
17 + 6p = 9
17 + 6p = 9
17 को दायें पक्ष में पक्षांतरण करने पर,
6p = 9 – 17
या 6p = -8
या p = \(\frac{-8}{6}\)
∴ p = \(\frac{-4}{3}\)

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1

प्रश्न 12.
\(\frac{x}{3}\) + 1 = \(\frac{7}{15}\)
हल :
\(\frac{x}{3}\) + 1 = \(\frac{7}{15}\)
1 को पक्षांतरण करने पर,
\(\frac{x}{3}\) + 1 – 1 = \(\frac{7}{15}\) – 1
या \(\frac{x}{3}\) = \(\frac{7-15}{15}\)
या \(\frac{x}{3}\) = \(\frac{-8}{15}\)
15x = -8 × 3 (कैंची गुणा करने पर)
या x = \(\frac{-8}{15}\) × 3
∴ x = \(\frac{-8}{5}\)

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1 Read More »

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

Haryana State Board HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 6 दहन और ज्वाला

HBSE 8th Class Science दहन और ज्वाला InText Questions and Answers

पहेली बूझो

(पृष्ठ संख्या – 64)

प्रश्न 1.
हमें बताया गया था कि भोजन हमारे शरीर के लिए एक ईंधन है।
उत्तर:
हाँ, भोजन हमारे शरीर के लिए एक ईंधन है क्योंकि भोजन हमारे शरीर में ऑक्सीजन से अभिक्रिया कर अपघटित होता है और इस अभिक्रिया से ऊष्मा उत्पन्न होती है।

(पृष्ठ संख्या – 66)

प्रश्न 2.
हमने पढ़ा है कि सूर्य अपनी ऊष्मा और प्रकाश दोनों उत्पन्न करता है । क्या यह भी एक प्रकार का दहन है?
उत्तर:
सूर्य में प्रकाश और ऊष्मा दोनों नाभिकीय अभिक्रियाओं द्वारा उत्पन्न होते हैं।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

HBSE 8th Class Science दहन और ज्वाला Textbook Questions and Answers

प्रश्न 1.
बहन की परिस्थितियों की सूची बनाइए ।
उत्तर:
दहन के लिए आवश्यक परिस्थितियाँ –
1. ऑक्सीजन की उपस्थिति
2. ईंधन या ज्वलनशील की उपस्थिति
3. पदार्थ का निम्न ज्वलन ताप ।

प्रश्न 2.
रिक्त स्थानों की पूर्ति कीजिए।
(क) लकड़ी और कोयला जलने से वायु का ……………….. होता है।
(ख) घरों में काम आने वाला एक द्रव ईंधन ……………….. है।
(ग) जलना प्रारम्भ होने से पहले ईंधन को उसके ……………….. तक गर्म करना आवश्यक है।
(घ) तेल द्वारा उत्पन्न आग को ……………….. द्वारा नियंत्रित नहीं किया जा सकता।
उत्तर:
(क) प्रदूषण
(ख) एलपीजी
(ग) ज्वलन-ताप
(घ) पानी।

प्रश्न 3.
समझाइए कि मोटर वाहनों में सीएनजी के उपयोग से हमारे शहरों का प्रदूषण किस प्रकार कम हुआ है?
उत्तर:
सीएनजी के दहन के परिणामस्वरूप कोई भी हानिकारक गैस जैसे – नाइट्रोजन डाइ-ऑक्साइड, सल्फर डाइआक्साइड आदि उत्पन्न नहीं होतीं । ये गैसें ही मुख्य रूप से वायु प्रदूषण का कारण होती हैं । पेट्रोल जलने के दौरान जले कार्बन कण छोड़ती है, जो दमा जैसे श्वास रोग उत्पन्न करते हैं, जबकि सीएनजी जलने पर ऐसे कण नहीं छोड़ती है। अत: मोटर वाहनों में सीएनजी के उपयोग
से वायु प्रदूषण कम होता है ।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 4.
ईंधन के रूप में एलपीजी और लकड़ी की तुलना कीजिए।
उत्तर:

लकड़ीएल.पी.जी.
1. इसका ऊष्मीय मान कम होता है।1. इसका ऊष्मीय मान उच्च होता है।
2. लकड़ी का ज्वलनांक अधिक होता है।2. एल.पी.जी. का ज्वलनांक कम होता है।
3. यह धुएँ के साथ जलती है।3. यह बिना धुआँ किए जलती है।
4. लकड़ी के जलने पर CO2 तथा कम वायु में CO (कार्बन मोनोक्साइड) गैसें उत्पन्न होती हैं।4. इसके जलने पर कोई विषैली गैस उत्पन्न नहीं होती है।
5. ठोस और भारी होने के कारण इसे भण्डारित करना आसान नहीं होता है।5. इसको आसानी से भण्डारित किया जा सकता है।
6. इसको जलाने पर राख अवशेष बनती है।6. इसको जलाने पर अवशेष नहीं बचता है।

प्रश्न 5.
कारण बताइए-
(क) विद्युत उपकरण से संबद्ध आग पर नियंत्रण पाने हेतु जल का उपयोग नहीं किया जाता ।
(ख) एलपीजी लकड़ी से अच्छा घरेलू ईंधन है।
(ग) कागज स्वयं सरलता से आग पकड़ लेता है जबकि ऐलुमिनियम पाइप के चारों ओर लपेटा गया कागज का टुकड़ा आग नहीं पकड़ता।
उत्तर:
(क) जल विद्युत का सुचालक है। इसीलिए विद्युत उपकरण से संबद्ध आग पर नियंत्रण पाने हेतु जल का उपयोग नहीं करते । इससे विद्युत झटका लगने से जान जाने का खतरा होता है ।
(ख) लकड़ी की अपेक्षा एलपीजी आसानी से जलती है और अधिक ऊष्मा उत्पन्न करती है । एलपीजी के दहन से लकड़ी की तुलना में वायु प्रदूषण नगण्य ही होता है ।
(ग) कागज का ज्वलन ताप कम होता है, जबकि ऐलुमिनियम पाइप के साथ कागज लपेटने पर दहन के लिए यह आवश्यक है कि ऐलुमिनियम को उसके ज्वलन ताप तक गर्म किया जाये, जिसके लिए ज्यादा मात्रा में ऊष्मा की आवश्यकता होती है। अतः कागज स्वयं सरलता से आग पकड़ लेता है जबकि ऐलुमिनियम पाइप के चारों ओर लपेटा कागज का टुकड़ा आग आसानी से नहीं पकड़ता ।

प्रश्न 6.
मोमबत्ती की चाला का चिह्नित चित्र बनाइये ।
उत्तर:
HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला -1

प्रश्न 7.
ईंधन के ऊष्मीय मान को किस मात्रक द्वारा प्रदर्शित किया जाता है?
उत्तर:
ईधन का ऊष्मीय मान किलोजूल प्रति किलोग्राम के पदों में व्यक्त किया जाता है।

प्रश्न 8.
समझाइए कि CO2 किस प्रकार आग को नियंत्रित करती है।
उत्तर:
CO2 गैस वायु से भारी होती है । इसलिए यह जलती हुई वस्तु के चारों ओर आवरण कर ऑक्सीजन की मात्रा को कम कर देती है तथा वातावरण से ऑक्सीजन के प्रवाह को वस्तु तक नहीं पहुंचने देती तथा जलने वाली वस्तु का ताप उसके ज्वलन ताप से काफी हद तक कम कर देती है, जिस कारण आग बुझ जाती है ।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 9.
हरी पत्तियों के ढेर को जलाना कठिन होता है, परन्तु सूखी पत्तियों में आग आसानी से लग जाती है, समझाइए।
उत्तर:
हरी पत्तियों का ज्वलन ताप सूखी पत्तियों से अधिक होता है, क्योंकि हरी पत्तियों में नमी की मात्रा अधिक होती है तथा हरी पत्तियों के ढेर में ऑक्सीजन की मात्रा कम होती है। परन्तु सुखी पत्तियों में नमी की मात्रा कम होती है तथा इनके ढेर में ऑक्सीजन की मात्रा अधिक होती है। इसलिए हरी पत्तियों के ढेर को जलाना कठिन होता है।

प्रश्न 10.
सोने और चाँदी को पिघलाने के लिए स्वर्णकार ज्वाला के किस क्षेत्र का उपयोग करते हैं और क्यों ?
उत्तर:
स्वर्णकार ज्वाला के सबसे ऊपरी अदीप्त, नीले क्षेत्र का उपयोग करते हैं, क्योंकि ज्वाला का बाह्य पूर्ण दहन क्षेत्र सबसे अधिक ऊष्मा वाला होता है। सोना और चाँदी का गलनाक बहुत अधिक होता है। इसलिए उन्हें पिघलन के लिए अधिक ऊष्मा की आवश्यकता होती है।

प्रश्न 11.
एक प्रयोग में 4.5 Kg. ईधन का पूर्णतया दहन किया गया । उत्पन्न ऊष्मा का मान 1,80,000 Kj. था। ईंधन का ऊष्मीय मान परिकलित कीजिए।
उत्तर:
ईधन की मात्रा (द्रव्यमान) = 4.5 Kg.
4.5 Kg. ईंधन जलाने पर प्राप्त ऊष्मा = 180,000 KJ
1 Kg. ईधन को पूर्णतया दहन करने पर उत्पन्न ऊष्मा = 180,000
4.5 = 40,000 KJ.
ईंधन का ऊष्मीय मान – 40,000 kJ/kg.

प्रश्न 12.
क्या जंग लगने के प्रक्रम को दहन कहा जा संकता है ? विवेचना कीजिए ।
उत्तर:
नहीं, जंग लगने की प्रक्रिया में धातु वातावरण की ऑक्सीजन व नमी से क्रिया कर ऑक्साइड बनाती है जो उसके पृष्ठ पर दिखाई देती है, जबकि दहन प्रक्रम में वस्तु ऑक्सीजन की उपस्थिति में जलती है । दहन एक तीव्र प्रक्रिया है जबकि जंग लगना धीमी प्रक्रिया है। साथ ही दहन ऊष्मा के साथ ज्वाला भी उत्पन्न करता है। जबकि जंग केवल ऊष्मा उत्पन्न करता है। इस कारण जंग लगने की प्रक्रिया का दहन नहीं कहा जा सकता ह।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 13.
आबिदा और रमेश ने एक प्रयोग किया जिसमें बीकर में रखे जल को गर्म किया गया । आबिदा ने बीकर को मोमबत्ती चाला के पीले भाग के पास रखा। रमेश ने बीकर को ज्वाला के सबसे बाहरी भाग के पास रखा । किसका पानी कम समय में गर्म हो जाएगा ।
उत्तर:
रमेश के बीकर का जल पहले गर्म होगा क्योंकि ज्वाला का सबसे बाहरी भाग (नीला क्षेत्र) अन्य भागों की तुलना में सबसे अधिक गर्म होता है ।

HBSE 8th Class Science कोयला और पेट्रोलियम Important Questions and Answers

बहुविकल्पीय प्रश्न

1. मैग्नीशियम जलकर (दहन होकर) क्या बनाता है?
(अ) मैग्नीज,
(ब) मैग्नीशियम ऑक्साइड
(स) मैग्नीशियम हाइड्रॉक्साइड
(द) मैग्नीशियम क्लोराइड ।
उत्तर:
(ब) मैग्नीशियम ऑक्साइड

2. मोमबत्ती के आंशिक दहन वाले मध्य भाग का रंग होता है
(अ) काला
(ब) नीला
(स) पीला।
(द) उपरोक्त में से कोई नहीं ।
उत्तर:
(ब) नीला

3. ईंधन के ऊष्यीय मान का मात्रक है –
(अ) न्यूटन
(ब) Kg/KJ
(स) °C
(द) KJ/Kg
उत्तर:
(द) KJ/Kg

4. पेट्रोल का ऊष्मीय मान है –
(अ) 55,000 KJ/Kg.
(ब) 45,000 KJ/Kg
(स) 6,000-8.000 KJ/Kg
(द) 1,50,000 KJ/Kg.
उत्तर:
(ब) 45,000 KJ/Kg

5. ज्वलनशील पदार्थों का ज्वलन ताप होता है –
(अ) बहुत कम
(ब) बहुत अधिक
(स) न बहुत अधिक न बहुत कम
(द) उपरोक्त में से कोई नहीं ।
उत्तर:
(अ) बहुत कम

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

6. ईंधन के अपूर्ण दहन से बनने वाली गैस है
(अ) कार्बन डाईऑक्साइड
(ब) हाइड्रोजन
(स) कार्बन मोनोक्साइड
(द) सल्फर डाइऑक्साइड।
उत्तर:
(स) कार्बन मोनोक्साइड

रिक्तस्थान पूर्ति

(क) वह न्यूनतम ताप जिस पर कोई पदार्थ जलने लगता है, उसका ……………. कहलाता है।
(ख) ईधन के ऊष्मीय मान को ……………. मात्रक द्वारा प्रदर्शित किया जाता है।
(ग) ईंधन का अपूर्ण दहन ……………. गैस देता है।
(घ) वायु में कार्बन डाइऑक्साइड गैस की अधिक मात्रा ……………. का कारण बनती है।
उत्तर:
(क) ज्वलन-ताप
(ख) किलोजूल प्रति किलोग्राम
(ग) कार्बन मोनोक्साइड
(घ) विश्व ऊष्णन।

सुमेलन

कॉलम ‘अ’कॉलम ‘ब’
(i) मिट्टी का तेल(क) द्रव ईंधन
(ii) लकड़ी का कोयला(ख) विश्व ऊष्णन का कारण
(iii) पेट्रोल(ग) अम्ल वर्षा का कारण
(iv) कार्बन डाइऑक्साइड(घ) ज्वाला देता है
(v) सल्फर और नाइट्रोजन के ऑक्साइड(ङ) ज्वाला नहीं देता

उत्तर:

कॉलम ‘अ’कॉलम ‘ब’
(i) मिट्टी का तेल(घ) ज्वाला देता है
(ii) लकड़ी का कोयला(ङ) ज्वाला नहीं देता
(iii) पेट्रोल(क) द्रव ईंधन
(iv) कार्बन डाइऑक्साइड(ख) विश्व ऊष्णन का कारण
(v) सल्फर और नाइट्रोजन के ऑक्साइड(ग) अम्ल वर्षा का कारण

सत्य / असत्य कथन

(क) मोमबत्ती ज्वाला के साथ जलती है जबकि कोयला नहीं।
(ख) ईधन के ऊष्मीय मान को किलोजूल प्रति किलोग्राम मात्रक द्वारा प्रदर्शित करते हैं।
(ग) ईंधन के अपूर्ण दहन में कार्बन डाइऑक्साइड गैस बनती है।
(घ) पृथ्वी के वातावरण के तापमान में वृद्धि अम्ल वर्षा कहलाती है।
उत्तर:
(क) सत्य
(ख) सत्य
(ग) असत्य
(घ) असत्य।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

अति लघु उत्तरीय प्रश्न

प्रश्न 1.
कोई तीन तरल ईंधनों के नाम लिखिए ।
उत्तर:
डीजल, पेट्रोल, केरोसिन तेल (मिट्टी का तेल) आदि ।

प्रश्न 2.
दहन से क्या तात्पर्य है ?
उत्तर:
वह रासायनिक प्रक्रम जिसमें पदार्थ ऑक्सीजन के साथ अभिक्रिया करके ऊष्मा प्रदान करता है, दहन कहलाता है।

प्रश्न 3.
ज्वलन ताप की परिभाषा लिखिए ।
उत्तर:
वह न्यूनतम ताप जिस पर कोई पदार्थ आग पकड़ लेता है एवं जलने लगता है, उस पदार्थ का ज्वलन ताप कहलाता है।

प्रश्न 4.
किन्हीं दो ज्वलनशील पदार्थों के नाम लिखिए।
उत्तर:
पेट्रोल एवं द्रवित पेट्रोलियम गैस।

प्रश्न 5.
विद्युत द्वारा लगी आग बुझाने के लिए किस प्रकार के अग्निशामक का उपयोग होता है।
उत्तर:
कार्बन ट्रेटा क्लोराइड नामक अग्निशामक ।

प्रश्न 6.
दहन के प्रकार लिखिए ।
उत्तर:
तीव्र दहन, स्वतः दहन एवं विस्फोट।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 7.
तीन दहन किसे कहते हैं?
उत्तर:
जब गैस तेजी से जलने लगती है तथा ऊष्मा और प्रकाश उत्पन्न करती है, तब यह दहन तीव्र दहन कहलाता है।

प्रश्न 8.
स्वतः दहन किसे कहते हैं ?
उत्तर:
ऐसे पदार्थ जो कमरे के ताप पर वायु में जल उठते हैं । जैसे- फॉस्फोरस । यह स्वतः दहन कहलाता है।

प्रश्न 9.
मोमबत्ती की ज्वाला के क्षेत्रों के नाम लिखिए।
उत्तर:
ठंडा अंदरूनी क्षेत्र, मध्य क्षेत्र, बाह्य अदीप्त क्षेत्र।

प्रश्न 10.
किसी ईंधन के ऊष्मीय मान से क्या तात्पर्य है?
उत्तर:
किसी ईंधन के 1 किलोग्राम के पूर्ण दहन से प्राप्त ऊष्मा ऊर्जा की मात्रा, उसका ऊष्मीय मान कहलाती है।

प्रश्न 11.
विश्व ऊष्णन किसे कहते हैं?
उत्तर:
पृथ्वी के वातावरण के तापमान में वृद्धि विश्व ऊष्णन कहलाती है।

प्रश्न 12.
विश्व ऊष्णन का कारण क्या है?
उत्तर:
वायु में कार्बन डाईऑक्साइड की बढ़ी मात्रा को विश्व ऊष्णन का कारण माना जाता है।

प्रश्न 13.
अम्लीय वर्षा के लिए कारक दो गैसों के नाम लिखिए।
उत्तर:
(i) नाइट्रोजन डाइऑक्साइड
(ii) सल्फर डाइऑक्साइड।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

लघु उत्तरीय प्रश्न

प्रश्न 1.
परिभाषा लिखिए-
(1) बहन
(2) दाह्य
उत्तर:
(1) दहन : ऐसा प्रक्रम जिसमें पदार्थ को ऑक्सीजन में जलाने से ऊष्मा पैदा होती है ।
(2) दाह्य : दहन की क्रिया में जिस पदार्थ का दहन होता है । दाह्य कहलाता है।

प्रश्न 2.
कुछ दाह्य और अदाह्य पदार्थों के नाम लिखिए। (क्रियाकलाप)
उत्तर:
दाह्य पदार्थ- लकड़ी, कागज, मिट्टी का तेल, स्ट्रा, काष्ठ कोयला एवं माचिस की तीलियाँ। अदाह्य पदार्थ- लोहे की कीलें, पत्थर का टुकड़ा एवं

प्रश्न 3.
एक लकड़ी के कोयले का जलते हुए टुकड़े को एक लोहे की प्लेट पर रखकर एक पारदर्शक प्लास्टिक जार से ढकने पर क्या होता है और क्यों? (क्रियाकलाप)
उत्तर:
कुछ समय बाद लकड़ी का कोयला जलना बंद हो जाता है क्योंकि इस पर प्लास्टिक जार ढकने से ऑक्सीजन की कमी हो जाती है।

प्रश्न 4.
कागज के बने कप में कागज के बिना जले पानी कैसे उबल जाता है ? (क्रियाकलाप)
उत्तर:
कागज के कप में पानी को गर्म करते समय बर्नर द्वारा दी गई ऊष्मा कागज के कप में उसमे रखे हुए पानी को स्थानान्तरित हो जाती है जिससे पानी का ताप बढ़ता जाता है तथा अन्त में पानी उबलने लगता है । कागज को प्रदान की जाने वाली ऊष्मा तुरन्त ही जल को स्थानान्तरित होने के कारण कागज अपने ज्वलन ताप तक नहीं पहुँच पाता तथा कागज जलने से बचा रहता है।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 5.
आग उत्पन्न करने के लिए क्या आवश्यकताएँ
उत्तर:
आग उत्पन्न करने के लिए निम्नलिखित तीन आवश्यकताएँ हैं-
(i) इंधन
(ii) वायु (ऑक्सीजन आपूर्ति हेत)
(iii) ऊष्मा (ईधन का ताप उसके ज्वलन ताप से अधिक करने हेतु)।

प्रश्न 6.
आग बुझाने के लिए सामान्यतया जल का उपयोग क्यों किया जाता है ?
उत्तर:
आग लग जाने पर जल डालने पर जलने वाले पदार्थ का ज्वलन ताप कम हो जाता है, ऐसा करने से आग का फैलना रुक जाता है । जलं वाष्प, ज्वलनशील पदार्थ को घेर लेता है जिससे ऑक्सीजन की आपूर्ति रुक जाता है तथा आग बुझ जाती है । आग बुझाने हेतु वायु का प्रवाह रोक कर या ईंधन का ताप कम करके आग पर नियंत्रण करने का प्रयास किया जाता है।

प्रश्न 7.
तेल या पेट्रोल में लगी आग को हम जल द्वारा नहीं बुझा सकते क्यों ?
उत्तर:
जल तेल से भारी होता है अत: तेल में लगी आग में जल को डालने पर जल नीचे चला जाता है तथा तेल ऊपर तैरकर जलता रहता है, अतः इसके लिए हम जल के स्थान पर कार्बन डाइऑक्साइड (Co) का उपयोग करते हैं जो ऑक्सीजन से भारी होने के कारण आग को एक कम्बल की भांति आवरण रूप दे देती है। इससे ईंधन एवं ऑक्सीजन (वायु से प्राप्त होने वाली) का सम्पर्क टूट जाता है जिससे आग पर नियंत्रण हो जाता है।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 8.
दहन के प्रकारों को समझाइए।
उत्तर:
दहन निम्नलिखित प्रकारों का होता है-
(i) तीन दहन- कुछ पदार्थ बहुत छोटी सी चिंगारी द्वारा ही जलने लगते हैं; जैसे- गैस लाइटर द्वारा गैस का जलना आदि । इस प्रकार के दहन को तीव्र दहन कहते हैं ।
(ii) स्वतः दहन- कुछ पदार्थ बिना किसी प्रत्यक्ष कारण के, अचानक लपटों के साथ जल उठते हैं, इस प्रकार का दहन स्वतः दहन कहलाता है। जैसे – फॉस्फोरस का कमरे के ताप पर जलना आदि ।
(iii) विस्फोट- इस प्रकार का दहन पटाखों में पाया जाता है । पटाखों के जलने पर आकस्मिक अभिक्रिया होने के कारण ऊष्मा, प्रकाश एवं ध्वनि उत्पन्न होती है।

प्रश्न 9.
दहन क्रिया में कौन से पदार्थ ज्वाला प्रदान करते (क्रियाकलाप),
उत्तर:
दहन क्रिया में सभी पदार्थ ज्वाला प्रदान नहीं करते हैं । दहन के समय वाष्पित होने वाले पदार्थ ज्वाला का निर्माण करते हैं । जैसे – मिट्टी के तेल का लैम्प, मोमबत्ती का पिघला हुआ मोम ज्वाला देते हैं, क्योंकि इनका वाष्पीकरण होता है । कोयला जलकर ज्वाला नहीं देता है क्योंकि यह वाष्पित नहीं होता है ।

प्रश्न 10.
सुनार फूंकनी का उपयोग क्यों करते हैं ?
उत्तर:
सुनार फूंकनी से ज्वाला के सबसे ऊपरी भाग को फॅक कर सोने पर मारते हैं, जिस कारण आग की प्रबलता बढ़ जाती है तथा सोना और चाँदी पिघलने लगते हैं । फूंक मारने के कारण । अधजले कार्बन के कण भी जलने लगते हैं और ऊष्मा अधिक प्राप्त होती है।
HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला -2

प्रश्न 11.
स्पष्ट कीजिए –
(1) ज्वलनशील पदार्थ
(2) ईंधन का ऊष्मीय मान ।
उत्तर:
(1) ज्वलनशील पदार्थ : ऐसे पदार्थ जिनका ज्वलन-ताप बहुत कम होता है और ज्वाला के साथ सरलतापूर्वक आग पकड़ लेते हैं, ज्वलनशील पदार्थ कहलाते हैं । उदाहरण- पेट्रोल, ऐल्कोहल, द्रवित पेट्रोलियम गैस (LPG) आदि ।
(2) ईंधन का ऊष्मीय मान : किसी ईंधन के किलोग्राम के पूर्ण दहन से प्राप्त ऊष्मा की मात्रा उसका ऊष्मीय मान कहलाती है । ईंधन का ऊष्मीय मान किलोजूल प्रति किलोग्राम (kJ/kg) मात्रक द्वारा प्रदर्शित किया जाता है।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 12.
एक बंद कमरे में कोयला जलाकर सोने से क्या खतरा होता है?
उत्तर:
एक बंद कमरे में कोयले को ऑक्सीजन पूर्णतया नहीं मिलने पर इसका अपूर्ण दहन कार्बन मोनोक्साइड देता है, जिससे कमरे में सो रहे व्यक्तियों की मृत्यु भी हो सकती है।

प्रश्न 13.
अम्लीय वर्षा से क्या तात्पर्य है ?
उत्तर:
सल्फर एवं नाइट्रोजन के ऑक्साइड वर्षा के जल में घुल जाते हैं तथा अम्ल बनाते हैं । ऐसी वर्षा अम्लीय वर्षा कहलाती है । अम्लीय वर्षा फसलों, भवनों एवं मृदा के लिए अत्यन्त हानिकारक होती है।

दीर्घ उत्तरीय प्रश्न

प्रश्न 1.
एक प्रयोग द्वारा सिद्ध कीजिए कि दहन के लिए वायु आवश्यक है। (क्रियाकलाप)
उत्तर:
प्रयोग-एक जलती मोमबत्ती को मेज के ऊपर रखिए। काँच की चिमनी को मोमबत्ती के ऊपर लकड़ी के दो गुटकों की सहायता से इस प्रकार रखिए कि वायु का चिमनी में प्रवेश होता
HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला -3
रहे (चित्र (a))। देखिए, ज्वाला को क्या होता है। अब लकड़ी के गुटके हटा कर चिमनी को मेज पर टिका दीजिए (चित्रं (b)) पुनः ज्वाला को देखिए। अंत में एक काँच की प्लेट चिमनी के ऊपर रख दीजिए। (चित्र (c))| ज्वाला को पुन: देखिए। तीनों स्थितियों में क्या होता है? निष्कर्ष-हम पाते हैं कि दहन के लिए वायु आवश्यक है। अवस्था (a) में मोमबत्ती निर्बाध रूप से जलती है, जबकि वायु चिमनी में नीचे से प्रवेश कर सकती है। अवस्था (b) में, जब चिमनी में नीचे से वायु प्रवेश नहीं कर पाती तो ज्वाला में कम्पन होता है और धुआँ उत्पन्न होता है। अवस्था (c) में, ज्वाला बुझ जाती है क्योंकि उसे वायु उपलब्ध नहीं हो पाती।

प्रश्न 2.
मोमबत्ती की ज्वाला के सभी क्षेत्रों का चित्र सहित स्पष्टीकरण कीजिए।
उत्तर:
ज्वाला के तीन मुख्य क्षेत्र होते हैं –
(1) गहरा आंतरिक क्षेत्र : यह ज्वाला का भीतरी ठंडा क्षेत्र है । इसमें मोम की गर्म वाष्प होती है ।
(2) दीप्त क्षेत्र : मध्य भाग चमकीला होता है । इस क्षेत्र में कार्बन के आधे जले कण होते हैं । इन कणों के चमकने से यह क्षेत्र चमकीला है । यह कण ज्वाला से धुएँ और काजल के रूप में उत्पन्न होते हैं।
(3) अदीप्त क्षेत्र : यह ज्वाला का सबसे बाहरी भाग है। जिसका रंग फीका नीला होता है । इस भाग में ऑक्सीजन ईंधन से मिलकर पूर्ण दहन करती है। यह सबसे बाहरी अदीप्त भाग है, जिसका तापमान सबसे अधिक होता है।
HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला -4

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

प्रश्न 3.
ईंधन को विस्तार से समझाइए ।
उत्तर:
ईंधन :
घरेलू और औद्योगिक उपयोगों से संबंधित ऊष्मा ऊर्जा के मुख्य स्रोत (काष्ठ, कोयला, पेट्रोल, मिट्टी का तेल इत्यादि) ईंधन कहलाते हैं । अच्छा ईंधन वह है जो आसानी से उपलब्ध हो जाए और सस्ता हो । अच्छा ईंध न वायु में सामान्य रूप से सुगमतापूर्वक जलता है, यह अधि क मात्रा में ऊष्मा उत्पन्न करता है । यह जलने के पश्चात् कोई अवांछनीय पदार्थ नहीं छोड़ता । संभवत: ऐसा कोई भी ईंधन नहीं है जिसे आदर्श ईंधन माना जा सके।

प्रश्न 4.
ऊष्मीय मान को समझाइए । कुछ ईंधनों के ऊष्मीय मानों को लिखिए। उत्तर-ऊष्मीय मान-किसी ईंधन के 1 किलोग्राम के पूर्ण दहन से प्राप्त ऊष्मा ऊर्जा की मात्रा, उसका ऊष्मीय मान कहलाती है । ईंधन के ऊष्मीय मान को किलोजूल प्रति किलोग्राम (KI/Kg) मात्रक द्वारा प्रदर्शित किया जाता है । कुछ ईंधनों के ऊष्मीय मान निम्नवत् हैं-

ईधनऊष्मीय मान (kj/kg)
गोबर के उपले6,000-8,000
लकड़ी17,000-22,000
कोयला25,000-33,000
पेट्रोल45,000
मिट्टी का तेल45,000
डीजल45,000
मेथेन50,000
सीएनजी50,000
एलपीजी55,000
जैव गैस35,000-40,000
हाइड्रोजन1,50,000

प्रश्न 5.
ईंधन के दहन से कौन-कौन से हानिकारक उत्पाद उत्पन्न होते हैं? समझाइए।
उत्तर:
ईंधन का बढ़ता हुआ उपभोग पर्यावरण पर अत्यन्त हानिकारक प्रभाव डालता है, इनमें से कुछ निम्नवत् हैं-
(1) लकड़ी, कोयले एवं पेट्रोल जैसे कार्बन ईंधन बिना जले कार्बन कण छोड़ते हैं । ये सूक्ष्म कण दमा एवं श्वास रोग उत्पन्न करते हैं।
(2) ईंधनों का अपूर्ण दहन होने पर यह कार्बन मोनोक्साइड गैस देते हैं । यह अत्यंत विषैली गैस है।
(3) अधिकांश ईंधनों के दहन के परिणामस्वरूप पर्यावरण में कार्बन डाइऑक्साइड गैस निकलती है । वायु में कार्बन डाइऑक्साइड गैस की अधिक मात्रा को ही विश्व ऊष्णन (Glabal warming) का कारण माना जाता है।
(4) कोयले तथा डीजल के दहन होने पर सल्फर डाइऑक्साइड गैस उत्सर्जित होती है जो कि दमघोंटू और संक्षारक गैस है । इसके अतिरिक्त पेट्रोल इंजन नाइट्रोजन के गैसीय ऑक्साइड छोड़ते हैं । सल्फर एवं नाइट्रोजन के ऑक्साइड वर्षा जल में घुल जाते हैं तथा अम्ल बनाते हैं जो वर्षा के जल से मिलकर अम्लीय वर्षा करते हैं, जो कि फसलों, मृदा के लिए अत्यंत हानिकारक होती है ।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला

दहन और ज्वाला Class 8 HBSE Notes in Hindi

→ दहन (Combustion) : रासायनिक प्रक्रम, जिसमें पदार्थ ऑक्सीजन से अभिक्रिया कर ऊष्मा देते हैं।

→ दाह्य पदार्थ (Combustible Substance) : वे पदार्थ जो जलने पर प्रकाश और ऊष्मा देते हैं, दाह्य पदार्थ कहलाते हैं।

→ अदाह्य पदार्थ (Non Combustible substance) : वे पदार्थ जो जलने पर न तो प्रकाश देते हैं और न ही ऊष्मा देते हैं, अदाह्य पदार्थ कहलाते हैं।

→ ज्वलन ताप (Ignition Temperature) : वह न्यूनतम ताप, जिस पर कोई पदार्थ जलने लगता है।

→ ज्वलनशील पदार्थ (Flammable Substance) : ऐसे पदार्थ जिनका ज्वलन-ताप बहुत कम होता है और जो ज्वाला के साथ सरलतापूर्वक आग पकड़ लेते हैं, ज्वलनशील पदार्थ कहलाते हैं।

→ अग्निशामक (Fire Extinguisher) : आम बुझाने वाला यत्र ।

→ तीव्र दहन (Rapid Combustion) : दहन जिसमें गैस तेजी से जलने लगती है एवं ऊष्मा और प्रकाश उत्पन्न करती हैं, तीव्र दहन कहलाता है।

→ स्वतः दहन (Spontaneous Combustion) : दहन जिसमें पदार्थ बिना किसी प्रत्यक्ष कारण के अचानक लपटों के साथ जल उठता है, स्वतः दहन कहलाता है।

→ विस्फोट (Explosion) : अभिक्रिया जिसमें बनी गैस बड़ी मात्रा में निकलकर ऊष्मा, प्रकाश और ध्वनि उत्पन्न करती है, विस्फोट कहलाती है।

→ ईंधन (Fuel) : वे पदार्थ जो पूर्ण दहन करने पर ऊष्मा उत्पन्न करते हैं, ईंधन कहलाते हैं।

→ ऊष्मीय मान (CalorificValue) : किसी ईंधन के 1 किलोग्राम के पूर्ण दहन से प्राप्त ऊष्मा ऊर्जा की मात्रा, उसका ऊष्मीय मान कहलाती है।

→ विश्व ऊष्णन (Global Warming) : पृथ्वी के वातावरण में धीमी गति से होने वाली ताप की वृद्धि ।

→ अम्ल वर्षा (Acid Rain) : जब सल्फर और नाइट्रोजन के ऑक्साइड वर्षा जल में घल जाते हैं एवं अम्ल बनाते हैं, तब ऐसी वर्षा अम्ल वर्षा कहलाती है।

HBSE 8th Class Science Solutions Chapter 6 दहन और ज्वाला Read More »

HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2

Haryana State Board HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2

प्रश्न 1.
निम्नलिखित संख्याओं को संख्या रेखा पर निरूपित कीजिए-
(i) \(\frac{7}{4}\)
(ii) \(\frac{-5}{6}\)
हल:
(i)
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 -1
बिन्दु P संख्या रेखा पर \(\frac{7}{4}\) को निरूपित करता है ।

(ii)
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 -2
बिन्दु P संख्या रेखा पर \(\frac{-5}{6}\) को निरूपित करता है ।

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.2

प्रश्न 2.
\(\frac{-2}{11}\), \(\frac{-5}{11}\), \(\frac{-9}{11}\) को संख्या रेखा पर निरूपित कीजिए।
हल:
बिन्दु P, Q, R क्रमशः संख्या रेखा पर \(\frac{-2}{11}\), \(\frac{-5}{11}\), \(\frac{-9}{11}\) निरूपित करता है ।

प्रश्न 3.
ऐसी पाँच परिमेय संख्याएँ लिखिए जो 2 से छोटी हों।
हल:
2 से छेटी पाँच परिमेय संख्याएँ निम्न हैं-
1, \(\frac{1}{2}\), 0, -1, \(-\frac{1}{2}\)

प्रश्न 4.
\(\frac{-2}{5}\) और \(\frac{1}{2}\) के मध्य दस परिमेय संख्याएँ ज्ञात कीजिए।
हल:
सर्वप्रथम \(\frac{-2}{5}\) और \(\frac{1}{2}\) को समान हर वाली परिमेय संख्याओं में बदलेंगे ।
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 -3

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.2

प्रश्न 5.
(i) \(\frac{2}{3}\) और \(\frac{4}{5}\)
(ii) \(\frac{-3}{2}\) और \(\frac{5}{3}\)
(iii) \(\frac{1}{4}\) और \(\frac{1}{2}\) के मध्य पाँच परिमेय संख्याएँ ज्ञात कीजिए।
हल:
(i) सर्वप्रथम \(\frac{2}{3}\) और \(\frac{4}{5}\) को समान हर वाली संख्याओं में बदलेंगे ।
\(\frac{2 \times 20}{3 \times 20}=\frac{40}{60}\) और \(\frac{4 \times 12}{5 \times 12}=\frac{48}{60}\)
अत: \(\frac{40}{60}\) और \(\frac{48}{60}\) के मध्य पाँच परिमेय संख्याएँ निम्न है –
\(\frac{41}{60}\), \(\frac{42}{60}\), \(\frac{43}{60}\), \(\frac{44}{60}\), \(\frac{45}{60}\)

(ii) सर्वप्रथम \(-\frac{3}{2}\) और \(\frac{5}{3}\) को समान हर वाली संख्याओं में बदलेंगे ।
\(-\frac{3 \times 3}{2 \times 3}\) और \(\frac{5 \times 2}{3 \times 2}\)
⇒ \(\frac{-9}{6}\) और \(\frac{10}{6}\)
अत: \(\frac{-9}{6}\) और \(\frac{10}{6}\) के मध्य 5 परिमेय संख्याएँ निम्न है –
\(\frac{-8}{6}\), \(\frac{-7}{6}\), \(\frac{-6}{6}\),\(\frac{-5}{6}\), \(\frac{-4}{6}\) या, \(\frac{-8}{6}\), \(\frac{-7}{6}\), 0,\(\frac{2}{6}\), \(\frac{3}{6}\)

(iii) सर्वप्रथम \(\frac{1}{4}\) और \(\frac{1}{2}\) को समान हर वाली संख्याओं में बदलेंगे ।
\(\frac{1 \times 8}{4 \times 8}\) और \(\frac{1 \times 16}{2 \times 16}\)
⇒ \(\frac{8}{2}\) और \(\frac{16}{32}\)
अत: \(\frac{8}{32}\) और \(\frac{16}{32}\) के मध्य पाँच परिमेय संख्याएँ निम्न है –
\(\frac{9}{32}\), \(\frac{10}{32}\), \(\frac{11}{32}\), \(\frac{12}{32}\), \(\frac{13}{32}\)

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.2

प्रश्न 6.
-2 से बड़ी पाँच परिमेय संख्याएँ लिखिए।
हल:
-2 से बड़ी पाँच परिमेय संख्याएँ निम्न है –
\(-\frac{3}{2}\), -1, \(-\frac{1}{2}\), 0, \(\frac{1}{2}\)

प्रश्न 7.
\(\frac{3}{5}\) और \(\frac{3}{4}\) के बीच में दस परिमेय संख्याएँ ज्ञात कीजिए।
हल:
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 -4

HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.2 Read More »

HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1

Haryana State Board HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1

प्रश्न 1.
उचित गुणधर्मों के उपयोग से निम्नलिखित का मान ज्ञात कीजिए-
(i) \(\frac{2}{3} \times \frac{3}{5}+\frac{5}{2}-\frac{3}{5} \times \frac{1}{6}\)
(ii) \(\frac{2}{5} \times\left(\frac{-3}{7}\right)-\frac{1}{6} \times \frac{3}{2}+\frac{1}{14} \times \frac{2}{5}\)
हल :
(i) \(\frac{2}{3} \times \frac{3}{5}+\frac{5}{2}-\frac{3}{5} \times \frac{1}{6}\)
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1 -1

(ii)
HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1 -2

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

प्रश्न 2.
निम्नलिखित में से प्रत्येक के योज्य प्रतिलोम लिखिए
(i) \(\frac{2}{8}\)
(ii) \(\frac{-5}{9}\)
(iii) \(\frac{-6}{5}\)
(iv) \(\frac{2}{-9}\)
(v) \(\frac{19}{-6}\)
हल :
(i) \(\frac{-2}{8}\) का योज्य प्रतिलोम, \(\frac{2}{8}\) है; क्योंकि
\(\frac{-2}{8}\) + \(\frac{2}{8}\) = \(\frac{-2 + 2}{8}\) = \(\frac{0}{8}\) = 0

(ii) \(\frac{-5}{9}\) का योज्य प्रतिलोम = \(\frac{5}{9}\)

(iii) \(\frac{-6}{5}\) = \(\frac{6}{5}\) का योज्य प्रतिलोम = \(\frac{-6}{5}\)

(iv) \(\frac{2}{-9}\) का योज्य प्रतिलोम = \(\frac{2}{9}\)

(v) \(\frac{19}{-6}\) का योज्य प्रतिलोम = (v) \(\frac{19}{6}\)

प्रश्न 3.
(i) x = \(\frac{11}{15}\)
(ii) x = \(-\frac{13}{17}\) के लिए सत्यापित कीजिए कि – (-x) = x.
हल :
(i) x = \(\frac{11}{15}\)
x = \(\frac{11}{15}\) का योज्य प्रतिलोम = -x = \(\frac{-11}{15}\)
अर्थात् \(\frac{-11}{15}\) का योज्य प्रतिलोम = \(\frac{11}{15}\)
अभवा, –\(\frac{-11}{15}\) = \(\frac{11}{15}\) अर्थात् -(-x) = x

(i) x =\(-\frac{13}{17}\)
x = \(\frac{13}{17}\) का योज्य प्रतिलोम = -x = \(-\frac{13}{17}\)
अर्थात् \(\frac{13}{17}\) का योज्य प्रतिलोम = \(-\frac{13}{17}\)
अभवा, –\(-\frac{13}{17}\) = \(\frac{13}{17}\) अर्थात् -(-x) = x;

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

प्रश्न 4.
निम्नलिखित के गुणनात्मक प्रतिलोम ज्ञात कीजिए
(i) -13
(ii) \(\frac{-13}{19}\)
(iii) \(\frac{1}{5}\)
(iv) \(\frac{-5}{8} \times \frac{-3}{7}\)
(v) -1 × \(\frac{-2}{5}\)
(vi) -1
हल :
(i) – 13 का गुणनात्मक प्रतिलोम = \(-\frac{1}{13}\)
क्योंकि, -13 × \(-\frac{1}{13}\) = 1 (\(\frac{a}{b} \times \frac{b}{a}=1\))

(ii) \(\frac{-13}{19}\) का गुणनात्मक प्रतिलोम = \(\frac{19}{-13}\)

(iii) \(\frac{1}{5}\) का गुणनात्मक प्रतिलोम = 5

(iv) \(\frac{-5}{8} \times \frac{-3}{7}\) = \(\frac{56}{15}\)
\(\frac{56}{15}\) का गुणनात्मक प्रतिलोम = \(\frac{56}{15}\)

(v) -1 × \(\frac{-2}{5}\) ⇒ \(\frac{2}{5}\) का गुणनात्मक प्रतिलोम = \(\frac{5}{2}\)

(vi) -1 का गुणनात्मक प्रतिलोम = \(\frac{1}{-1}\)

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

प्रश्न 5.
निम्नलिखित प्रत्येक में गुणन के अन्तर्गत | उपयोग किए गए गुणधर्म का नाम लिखिए-
(i) \(\frac{-4}{5} \times 1=1 \times \frac{-4}{5}=-\frac{4}{5}\)
(ii) \(-\frac{13}{17} \times \frac{-2}{7}=\frac{-2}{7} \times \frac{-13}{17}\)
(iii) \(\frac{-19}{29} \times \frac{29}{-19}\) = 1
हल :
(i) \(\frac{-4}{5} \times 1=1 \times \frac{-4}{5}=-\frac{4}{5}\) गुणनात्मक तत्समक है।

(ii) \(-\frac{13}{17} \times \frac{-2}{7}=\frac{-2}{7} \times \frac{-13}{17}\) क्रमविनिमेयता।

(iii) \(\frac{-19}{29} \times \frac{29}{-19}\) = 1 गुणनात्मक प्रतिलोम

प्रश्न 6.
\(\frac{6}{13}\) को \(\frac{-7}{16}\) के व्युत्क्रम से गुणा कीजिए।
Solution:
सर्वप्रथम, \(\frac{-7}{16}\) का व्युत्क्रम = \(\frac{16}{-7}\)
अतः प्रश्नानुसार, latex]\frac{6}{13}[/latex] × \(\frac{16}{-7}\) = \(\frac{96}{-91}\)

प्रश्न 7.
बताइए कौन-से गुणधर्म की सहायता से आप \(\frac{1}{3} \times\left(6 \times \frac{4}{3}\right)\) को \(\left(\frac{1}{3} \times 6\right) \times \frac{4}{3}\) के रूप में अभिकलन करते हैं?
हल:
सहचारिता नियम से \(\frac{1}{3} \times\left(6 \times \frac{4}{3}\right)\) को \(\left(\frac{1}{3} \times 6\right) \times \frac{4}{3}\) के रूप में अभिकलन करते हैं।

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

प्रश्न 8.
क्या -1\(\frac{1}{8}\) का गुणनात्मक प्रतिलोम \(\frac{8}{9}\) है? क्यों अथवा क्यों नहीं?
हल:
हम जानते हैं कि, -1\(\frac{1}{8}\) = \(\frac{-9}{8}\)
नहीं, \(\frac{-9}{8}\) का गुणनात्मक प्रतिलोम नहीं है।
क्योंकि \(\frac{-9}{8}\) × \(\frac{8}{-9}\) = -1

प्रश्न 8.
क्या 3\(\frac{1}{3}\) का गुणनात्मक प्रतिलोम 0.3 है? क्यों अथवा क्यों नहीं?
हल:
हमें ज्ञात है, 3\(\frac{1}{3}\) = \(\frac{10}{3}\) 0.3 = \(\frac{3}{10}\)
\(\frac{10}{3}\) का गुणनात्मक प्रतिलोम \(\frac{3}{10}\) है।
क्योंकि \(\frac{10}{8}\) × \(\frac{3}{10}\) = 1

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

प्रश्न 10.
लिखिए
(i) ऐसी परिमेय संख्या जिसका कोई व्युत्क्रम नहीं है।
(ii) परिमेय संख्याएँ जो अपने व्युत्क्रम के समान हैं।
(iii) परिमेय संख्या जो अपने ऋणात्मक के समान है।
हल:
(i) हम जानते हैं कि ऐसी कोई परिमेय संख्या नहीं है जिसे 0 से गुणन करके 1 मिलता हो। अतः परिमेय संख्या 0 का कोई व्युत्क्रम नहीं है।
(ii) हम जानते हैं कि 1 का व्युत्क्रम 1 है और -1 का व्युत्क्रम -1 है। अतः 1 और -1 ऐसी परिमेय संख्याएँ हैं जो स्वयं के व्युत्क्रम के समान हैं।
(iii) परिमेय संख्या 0 अपने ऋणात्मक -0 = 0 के बराबर है।

प्रश्न 11.
रिक्त स्थानों की पूर्ति कीजिए
(i) शून्य का व्युत्क्रम ___________ है।
हल:
नहीं

(ii) संख्याएँ ___________ तथा ___________ स्वयं के व्युत्क्रम हैं।
हल:
1, – 1

HBSE 8th Class Maths Solutions Chapter परिमेय संख्याएँ Ex 1.1

(iii)-5 का व्युत्क्रम ___________ है।
हल:
\(\frac{1}{x}\)

(iv) \(-\frac{1}{5}\) (x ≠ 0) का व्युत्क्रम ___________ है।
हल:
परिमेय संख्या

(v) दो परिमेय संख्याओं का गुणनफल हमेशा ___________ है।
हल:
परिमेय संख्या

(vi) किसी धनात्मक परिमेय संख्या का व्युत्क्रम ___________ है।
हल:
धनात्मक।

HBSE 8th Class Maths Solutions Chapter 1 परिमेय संख्याएँ Ex 1.1 Read More »

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6

Haryana State Board HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Exercise 2.6

निम्नलिखित समीकरणों को हल कीजिए

प्रश्न 1.
\(\frac{8 x-3}{3 x}\) = 2
हल :
\(\frac{8 x-3}{3 x}\) = 2
कैंची गुणा करने पर,
⇒ (8x – 3) × 1= 3x × 2
8x – 3= 6x
– 3 तथा 6x का पक्षान्तरण करने पर,
⇒ 8x – 6x = 3
⇒ 2x = 3
∴ x = \(\frac{3}{2}\)

प्रश्न 2.
\(\frac{9 x}{7-6 x}\) = 15
हल :
\(\frac{9 x}{7 – 6x}\) = \(\frac{15}{1}\)
कैंची गुणा करने पर,
⇒ 9x × 1 = (7 – 6x) × 15
⇒ 9x = 105 – 90x
90x का पक्षान्तरण करने पर,
⇒ 9x + 90x = 105
⇒ 99x = 105
⇒ x = \(\frac{105}{99}\) = \(\frac{35}{33}\)
अतः x = \(\frac{35}{33}\)

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6

प्रश्न 3.
\(\frac{z}{z+15}\) = \(\frac{4}{9}\)
हल :
\(\frac{z}{z+15}\) = \(\frac{4}{9}\)
⇒ 9z = 4(z + 15) (कैंची गुणा करने पर)
⇒ 9z = 4z + 60
⇒ 9z – 4z = 60
⇒ 5z = 60
⇒ z = \(\frac{60}{5}\)
अतः z = 12

प्रश्न 4.
\(\frac{3y+4}{2-6y}\) = \(\frac{-2}{5}\)
हल :
\(\frac{3y+4}{2-6y}\) = \(\frac{-2}{5}\)
कैंची गुणा करने पर,
⇒ 5(3y + 4) = – 2(2 – 6y)
⇒ 15y + 20 = – 4 +12y
⇒ 15y – 12y = – 4 – 20 (पक्षान्तरण करने पर)
⇒ 3y = – 24
⇒ y = \(\frac{-24}{3}\)
अतः y = -8

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6

प्रश्न 5.
\(\frac{7y+4}{y+2}\) = \(\frac{-4}{3}\)
हल :
\(\frac{7y+4}{y+2}\) = \(\frac{-4}{3}\)
कैंची गुणा करने पर,
⇒ 3(7y + 4) = -4(y + 2)
⇒ – 21y + 12 = – 4y – 8
⇒ – 21y + 4y = – 8 – 12 (पक्षान्तरण करने पर)
⇒ – 25y = – 20
⇒ y = \(-\frac{20}{25}\) = \(-\frac{4}{5}\)
अतः y = \(-\frac{4}{5}\)

प्रश्न 6.
हरी और हैरी की वर्तमान आयु का अनुपात 5 : 7 है । अब से 4 वर्ष बाद उनकी आयु का अनुपात 3 : 4 हो जायेगा । उनकी वर्तमान आयु ज्ञात कीजिए।
हल :
माना कि हरी और हैरी की वर्तमान आयु क्रमश : 5x तथा 7x हैं।
अत: 4 वर्ष बाद हरी की आयु = (5x + 4) वर्ष
तथा 4 वर्ष बाद हैरी की आयु = (7x + 4) वर्ष
4 वर्ष बाद उनकी आयु का अनुपात = 3 : 4
प्रश्नानुसार,
\(\frac{5x+4}{7x+4}\) = \(\frac{3}{4}\)
कैंची गुणा करने पर,
⇒ 3(7x + 4) = 4 (5x + 4)
⇒ 21x + 12 = 20x + 16
⇒ 21x – 20x = 16 – 12 (पक्षान्तरण करने पर)
∴ x = 4
अत: हरी की वर्तमान आयु = 5x = 5 × 4 = 20 वर्ष
तथा हैरी की वर्तमान आयु = 7x = 7 × 4 = 28 वर्ष

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6

प्रश्न 7.
एक परिमेय संख्या का हर उसके अंश से 8 अधिक है । यदि अंश में 17 जोड़ दिया जाए तथा हर में से 1 घटा दिया जाए, तब हमें में प्राप्त होता है । वह परिमेय संख्या ज्ञात कीजिए।
हल :
माना कि परिमेय संख्या का अंश =x
तब हर = (x+8)
तो परिमेय संख्या = \(\frac{x}{x+8}\)
अंश में 17 जोड़ने पर, नया अंश = (x + 17)
हर में से 1 घटाने पर, नया हर = (x + 8 – 1) = (x + 7)
तो प्राप्त नयी परिमेय संख्या = \(\frac{x+17}{x+7}\)
अतः प्रश्नानुसार, \(\frac{x+17}{x+7}\) = \(\frac{3}{2}\)
कैंची गुणा करने पर,
⇒ 2(x + 17) = 3(x +7 )
⇒ 2x + 34 = 3x + 21
⇒ 2x – 3x = 21 – 34 (पक्षान्तरण करने पर)
⇒ -x = -13
⇒ x = 13
∴ अंश = 13
हर (x + 8) = (13 + 8) ⇒ 21
अतः परिमेय संख्या = \(\frac{13}{21}\)

HBSE 8th Class Maths Solutions Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6 Read More »

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1

Haryana State Board HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1

प्रश्न 1.
दिए हुए प्रत्येक ठोस के लिए, दो दृश्य दिए गए हैं। प्रत्येक ठोस के लिए संगत, ऊपर से दृश्य और सामने से दृश्य का मिलान कीजिए। इनमें से एक आपके लिए किया गया है।
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 -1
हल:

चित्रसामने के दृश्यऊपर से दृश्य
(a) एक बोतल(iii)(iv)
(b) एक बाट(i)(v)
(c) एक फ्लास्क(iv)(ii)
(d) कप और प्लेट(v)(iii)
(e) एक डिब्बा(ii)(i)

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1

प्रश्न 2.
दिए हुए प्रत्येक ठोस के लिए, तीन दृश्य दिए गए हैं। प्रत्येक ठोस के संगत, ऊपर से दृश्य, सामने से दृश्य और पार्श्व दृश्य की पहचान कीजिए।
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 -2
हल:

(a) एक अलमारी-(i) सामने से(ii) पार्श्व(iii) ऊपर से
(b) एक माचिस की डिब्बी-(i) पार्श्व(ii)सामने से(iii) ऊपर से
(c) एक टेलीविजन-(i) सामने से(ii) पार्श्व(iii) ऊपर से
(d) एक कार-(i) सामने से(ii) पार्श्व,(iii)ऊपर से

प्रश्न 3.
दिये गये प्रत्येक ठोस के लिए, ऊपर से दृश्य, सामने से दृश्य और पार्श्व दृश्य की पहचान कीजिए
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 -3
हल :
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 -4

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1

प्रश्न 4.
दी हुई वस्तुओं के, सामने से दृश्य, पार्श्व दृश्य और ऊपर से दृश्य खींचिए-
HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 -5
हल :
विद्यार्थी चित्र की सहायता से स्वयं बनाएँ।

HBSE 8th Class Maths Solutions Chapter 10 ठोस आकारों का चित्रण Ex 10.1 Read More »

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Haryana State Board HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

HBSE 8th Class Science Conservation of Plants and Animals Textbook Questions and Answers

Question 1.
Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called ………….. .
(b) Species found only in a particular area is known as ………….. .
(c) Migratory birds fly to far away places because of …………. changes.
Answer:
(a) wildlife sanetuary
(b) Endemic species
(c) climate.

Question 2.
Differentiate between the following:
(a) Wildlife sanctuary and biosphere reserve.
(b) Zoo and wildlife sanctuary.
(c) Endangered and extinct species.
(d) Flora and fauna.
Answer:
(a) Wildlife sanctuary is a place where wild animals are protected and preserved. Here poaching or capturing any animal is strictly prohibited. Biosphere reserves are the protecting areas meant for only conservation of biodiversity i.e. animals and plants and even the microorganisms. It also helps to maintain the culture of that area. It contains many wildlife sancturies, national parks.

(b) Zoos are smaller places having some animals protected for the public view, while wildlife sancturies protect and conserve wild animals in their natural habitats. They are spread in vast areas.

(c) Endangered species are those species which are at the verge of extinction and which are required to be protected and conserved, while extinct species are those which no more exist on the earth.

(d) Flora is the term used for wide variety of plants while fauna is used to refer to all the varieties of animals.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 3.
Discuss the effects of deforestation on the following:
(a) Wild animals
(b) Environment
(c) Villages (Rural areas)
(d) Cities (Urban areas).
(e) Earth
(f) The next generation.
Answer:
(a) Wild animals:
When forests are cut, they leave many wild animals unsheltered. Their habitat is snatched away from them and they are left to die without their natural shelter.

(b) Environment:
Environment is adversely effected by deforestation as ecological balance is disturbed. Carbondioxide is not absorbed by plants and it gets accumulated to cause global warming.

(c) Villages (Rural areas):
Villages are depended upon forests to large extent. They are closely related to forests. Some adjoining villages have to face the wrath of wild animals as unhabitated animals run to nearby villages and cause danger to them. Morever they are devoid of other benefits like fruits, fuel, wood etc. they get from forests.

(d) Cities (Urban areas):
Cities are not directly effected by the cutting of forests because they are away from forests. But changes in climate effect cities. Calamities like flood and droughts do not spare cities.

(e) Earth:
Earth is the worst effected by deforestation. Its fertile land gets converted into deserts and its temperature rises. Its environment and climate changes.

(f) The Next generation:
The next generation will not be able to see many beautiful and attractive flora and fauna. They will not get a clean and cool environment. They will have to breath poisonous gases and have to live in jungles of concrete.

Question 4.
What will happen if:
(a) we go on cutting trees.
(b) the habitat of an animal is disturbed.
(c) the’top layer of soil is exposed.
Answer:
(a) We go on cutting trees:
If we go on cutting trees, the earth will loose its top fertile soil and get converted to desert. The ecological balance will get disturbed and floods and droughts will become more frequent. Many animals will loose their shelter and there will be a scarcity of things like fruits, paper, etc. we get from forests.

(b) When the habitat of an animal is disturbed, it becomes unprotected and unconserved. It becomes prone to extinction and if not conserved and protected, it will stop to exist anymore on the earth.

(c) When the top layer of the soil is exposed, the humus is lost and fertile soil gets converted into dry sand particles. It is called desertification.

Question 5.
Answer in brief:
(а) Why should we conserve biodiversity?
(b) Protected forests are also not completely safe for wild animals. Why?
(c) Some tribes depend on the jungle. How?
(d) What are the causes and consequences of deforestation?
(e) What is Red Data Book?
(f) What do you understand by the term migration?
Answer:
(a) We should conserve biodiversity to save it from becoming extinct.

(b) Protected forests are also not completely safe for wild animals because the poachers have found access in these areas an,d still kill the wild animals inside these protected areas.

(c) Some tribes are totally dependent on forests for their food, shelter, clothes and other requirements.

(d) Causes of the deforestation are growing urbanization and industrialization. Consequences are the desertification and natural calamities. It has also rendered many species of plants and animals unprotected and unconserved.

(e) Red Data Book is the record book and source book of all the endangered animals and plants. Different record books are maintained for endangered animals and endangered plants.

(f) The term migration means the phenomenon of periodical movement of a species of brids from its owu habitat to some other habitat due to changes in climate. It is for the purpose of breeding and other specific purposes.

Question 6.
In order to meet the ever- increasing demand in factories and for shelter, trees are being continually cut. Is it justified to cut trees for such projects? Discuss this in your class and prepare a brief report.
Answer:
It is not justified to cut forests for any project. We not only cut forests, we snatch away shelters from many plants, animals and birds. They also disturb the ecological balances and cause many natural calamities. So, we should preserve and protect our forests.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 7.
How can you contribute to the maintenance of green wealth of your locality? Make a list of actions to be taken byyou.
Answer:
We can grow new plants in our locality. Take turns to water them and take care of them. The existing plants should be properly nourished. All the residents should be taught about the coming dangers due to deforestation like global warming etc. They should be encouraged to help in the maintenance of green wealth of our locality.

Question 8.
Explain how deforestation lead to reduced rainfall.
Answer:
Deforestation leads to reduce rainfall because plants are the main agents to maintain the water cycle in the environment. Plants will not absorb water from the soil and will not evaporate water from their leaves to form clouds. If clouds will not be formed then how can we expect rainfall.

Question 9.
Find out about national parks in your state. Identify and show their location on the outlipe map of India.
Answer:
For self attempt.

Question 10.
Why should paper be saved? Prepare a list of the ways by which you can save paper.
Answer:
Paper is manufactured by using, pulps of tree bark. If we will keep on cutting forests indiscriminately, then where will we get pulp from. We should save paper to protect our trees, because paper can be recycled to make- new paper. We should not throw papers here and there. Newspapers, old books, notebooks and other papers should be collected and sold to kabadiwala, so that he can further supply it for recycling.

Question 11.
Complete the word puzzle:
Down .
1. Species on the verge of extinction.
2. A book carrying information about endangered species.
5. Consequence of deforestation.
Across
1. Species which have vanished.
3. Species found only in a particular habitat.
4. Variety and variability of a plant, animal and microorganisms.
HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals-1
Answer:
HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals-2

Extended Learning – Activities And Projects

1. Plant at least five different plants in your locality during this academic year and ensure their maintenance till they grow.
Answer:
For self attempt.

2. Promise yourself that this year you will gift at least 5 plants to your friends and relatives on their achievements, or on occasions like birthdays. Ask your friends to take proper care of these plants and encourage them to gift plants to their friends on such occasions. At the end of the year count the plants that have been gifted through this chain.
Answer:
For self attempt.

3. It is justified to prevent tribals from staying in the core area of the forest? Discuss the matter in your class and note down the points for and against the motion in your notebook.
Answer:
It is not justifiable in my Qpinin to prevent triabls from the core area of a forest. It is their natural habitat. They are not any threats to animals and plants as their life is centred around plants and animals. They don’t destroy forest or kill animals unnecessarily. Forest for them is an important as for other animals and plants.

4. Study the biodiversity of a park nearby. Prepare a detailed report with photographs and sketches of the flora and fauna.
Answer:
For self attempt.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

5. Make a list of the new information you have gathered from this chapter. Which information did you find the most interesting and why?
Answer:
(i) We have learnt how deforestation is destoryed biodiversity.
(ii) We have learnt about the actual meaning ofbiodiversity.
(iii) We have also gathered new information about extinct and endangerous animals.
(iv) We did not know anything about Red Data Book-but know we have learnt about it through this lesson.

6. Make a list of various uses of papers. Obseve currency notes carefully. Do you find any difference between a currency paper and paper of your notebook? Find out where currency paper is made.
Answer:
Paper is very useful for us.
(i) Our book and notebooks are all made up of paper.
(ii) Most of our currency is made up of paper.
(iii) All legal information and other important information are encoded on papers.
(iv) Paper is used to make bags, containers, package materials, etc. The paper used to make currency is stiffer than the normal paper and is transparent to some extent.

7. Karnataka Government had launched “Project Elephant” to save Asian elephants in the state. Find out about this and other such campaigns launched to protect threatened species.
Answer:
For self attempt.

Activities

Activity No. 7.1

Add more causes of deforestation to your list and classify them into natural and man-made.
Answer:
Natural causes of deforestation:
(i) lightning fires.

Man-made causes of deforestation:
(i) animal grazing.
(ii) Wood for fuel making houses.
(iii) Wood for manufacuring of paper.

Activity No. 7.2

Animal life is also affected by deforestation. How? List the points and discuss them in your class. ,
Answer:
(i) Animals loose their shelter as trees are out.
(ii) There is shortage of food for animals due to deforestation.
(iii) Animals become easy prey to hunters and bigger animals.
(iv) Food chains are disturbed.
(v) Animals have to bear the bad effects of natural calamities.

Activity No. 7.4

List the factors disturbing the biodiversity of your area. Some of these factors and human activities may disturb the biodiversity unknowingly. List these . human activities. How can these be checked? Discuss in your class and write a brief report in or notebook.
Answer:
Main factor affecting biodiversity of an area is cutting of trees and using the forest land for construction and industrialization. Excessive rains or droughts also offer the biodiversity of an area. Certain human activities which give rise to polluting end products also disturb the biodiversity unknowningly. When plants and animals do get clean environment they either fall ill or die, thus disturbance in biodiversity.

Activity No. 7.7

Visit a nearby zoo. Observe the conditions provided to the animals. Were they suitable for the animals? Can animals live in artificial setting instead of their natural habitats? In your opinion, will the animals be confortable in a zoo or in their natural habitat?
Answer:
Conditions provided in a zoo can never be compared with the natural habitat. The condition in a zoo are not exactly suitable for animals, although it is tried best to provide best living conditions to the animals in a zoo. But in my opinion animals be most comfortable in their natural habitat.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

HBSE 8th Class Science Conservation of Plants and Animals Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is cutting of forests called?
Answer:
Deforestations

Question 2.
Write any one cause of deforestation.
Answer:
Industrialization.

Question 3.
Name any one natural cause of deforestation.
Answer:
Forest fires.

Question 4.
Write any one consequence of deforestation.
Answer:
Increasing temperature of earth.

Question 5.
What is the process of conversion qf fertile soil into sand called?
Answer:
Desertification.

Question 6.
What are places where wild animals are protected called?
Answer:
Wildlife sanctuary.

Question 7.
What is the part of earth, which supports the biodiversity called?
Answer:
Biosphere reserve.

Question 8.
Name two wildlife sanctuaries hosted by Panchmarhi biosphere reserve.
Answer:
Bori and Panchmarhi.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 9.
What do you mean by Flora?
Answer:
All plants found in a particular area.

Question 10.
What do you mean by Fauna?
Answer:
All animals in a particular area.

Question 11.
What are species found only in a restricted area called?
Answer:
Endemic species.

Question 12.
Name any fauna of Panchmarhi Biosphere,reserve.
Answer:
Bison.

Question 13.
Name any three endangered species protected in our wildlife sanctuaries.
Answer:
Black buck, white eyed buck, golden cat.

Question 14.
What do National Parks preserve?
Answer:
Flora, fauna, landscape and historical objects.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 15.
Which is the first Reserve Forest of India?
Answer:
Satpura National Park.

Question 16.
Which prehistoric evidences of human life are found in Satpura National Park?
Answer:
Rock shelters of primitive humans.

Question 17.
When was Project Tiger launched?
Answer:
1st April, 1973.

Question 18.
What are the animals facing the danger of extinction are called?
Answer:
Endangered animals.

Question 19.
Name any one extinct animal.
Answer:
Dinosaurs.

Question 20.
Name the record book having records of all endangered animals and plants.
Answer:
Red Data Book.

Question 21.
Name some migratory birds.
Answer:
Surkhab, Bar Headed Goose, Great Cormorant.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 22.
How many times a paper can be recycled?
Answer:
5-7 times.

Question 23.
What do we call the restocking the plants by growing new plants?
Answer:
Reforestation.

Question 24.
What is plantation of new plants called?
Answer:
Afforestation.

Question 25.
What is the revised Forest Policy of 1952 called?
Answer:
Forest Act, 1980.

Short Answer Type Questions

Question 1.
What do you mean by deforestation?
Answer:
Indiscriminate cutting of forests for urbanization and industrialization is called deforestation. In simple words, deforestation means to clear the forests and use the land for other purposes.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 2.
Write some natural causes of deforestation.
Answer:
Natural causes of deforestation are those causes which are not initiated by human beings. Natural phenomenon like lightening on forests cause major forest fires, which can bum a large area of forests. Forest fires due to intense heat cause spontaneous combustion and bums a vast area of forest. Similarly, floods and severe droughts also cause damage to forests.

Question 3.
Write a few consequences of deforestation.
Answer:
Deforestation. has dangerous consequences which prove fatal for wildlife and human life. It gives rise to severe droughts and floods. It converts the fertile land into desert. It increases the temperature of the earth which causes melting of polar ice and glaciers. Many important species of plants, animals and birds become extinct and other stands at the verge of extinction.

Question 4.
How deforestation reduces rainfall?
Answer:
Deforestation disturbs the water cycle and reduces the rainfall. Increased amount of carbondioxide in environment increases the temperature of the earth. Which means there is less amount of water left on the earth. This reduces the evaporation of the water to form clouds thus reduced rainfall.

Question 5.
What do you mean by biodiversity?
Answer:
Biological diversity means the variety of living things existing on earth and their inter-relationship, as well as their relationship with the environment. In other words, variety of plants, animals and microorganisms generally found in an area is called its biodiversity.

Question 6.
What do you mean by endemic species?
Answer:
Species of animals and plants which are only found in a particular geographical area is called endemic species. These plants and animals cannot be found in any other geographical area e.g., wild mango arid gaint squirrel is endemic species of Panchmarhi.

Question 7.
What do you mean by wildlife sanctuaries?
Answer:
Wildlife sanctuaries are the protected areas where wild animals are protected and conserved. The wild animals are provided with their natural habitat. Their poaching and capturing is strictly prohibited m these protected areas.

Question 8.
What is a National Park?
Answer:
National Park is the protected vast area which conserves animals, plants, landscapes and even the historical objects. They are very large areas and can even protect whole sets of ecosystems in them. India has many such National Parks like Satpura National Park, Kaziranga National Park, etc.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 9.
What are the endangered and extinct animals?
Answer:
Endangered animals are those which are facing the danger to their existence. They are threatened to stop existing on the earth, if not saved. The extinct animals are those which do not exist any more on the earth e.g. Dinosaurs.

Question 10.
What is ecosystem?
Answer:
An ecosystem comprises of all the plants, animals, microorganisms in a particular area alongwith its non-living components like climate, soil, river, deltas etc.

Question 11.
What do you know about Project Tiger?
Answer:
Project Tiger was launched by Gqf*rtnment of India on 1st April, 1973 to enusre the maintenance of a viable populati on of tigers in our country. Tigers are one of the endangered species, so to preserve it Project Tiger was launched.

Question 12.
Why do birds migrate?
Answer:
Birds migrate from one place to another due to change in climate and for specific purposes like breeding etc. When weather in their natural habitat becomes cold they migrate to other lands covering long distances to lay eggs.

Question 13.
How does recycling of paper help preserving trees?
Answer:
Paper is made from the bark of trees. If used paper is recycled to make new papers, it means we do not have to cut more trees. So, recycling paper means protecting trees.

Question 14.
What do you mean by Habitat?
Answer:
Each species can live in particular environment according to their characteristics. So, the natural surroundings of a plant or animal species where they can grow, reproduce and live comfortably are called habitats, e.g. a lion can live in jungle, but not in a city. So jungle is the habitat of the lion.

Long Answer Type Questions

Question 1.
What is Deforestation? Write its causes.
Answer:
Deforestation means indiscriminate cutting of trees in forest. Forest lands are cleared to be used for urbanisation and industrialization.
Following are different causes of deforestation:
(i) Forest land is used for urbanization. As population is growing, so is growing the need for houses. So more and more land is required.
(ii) With growing population, industries are also growing. So the cleared land is used to set-up factories and industries.
(iii) Wood of forest is used for making furniture, doors, windows of buildings etc.
(iv) Wood is cut to use as fuel for cooking.
(v) Some natural causes like forest fires etc. also cause destruction of forests.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 2.
What are the consequences of deforestation? Explain.
Answer:
Deforestation has dire consequences. Following are the consequences of deforestation:
(i) Deforestation snatches away the natural habitat of many animals, plants and birds. It puts many species in endangered zone and many get extinct.
(ii) Deforestation causes natural calamities like floods, drought etc.
(iii) Reduced rainfall and increase in earth’s temperature has caused problems like Global warming.
(iv) Increased amount of carbondioxide and other gases pollute environment.
(v) Oxygen level is decreased as well as the water level.
(vi) Fertile top layer of soil gets converted into desert.

Question 3.
What is done for the conservation of wildlife?
Answer:
Various measures are taken to conserve wildlife. Reserved and protected areas like Biosphere reserve, Wildlife sanctuaries and National parks are formed.

Biosphere Reserves are the areas which support biodiversity and culture of the reserved area. Biosphere Reserve is a vast area which contains many other protected areas.

Wildlife Sanctuaries are the areas where wild animals are conserved and protected. It is the area which is restricted and activities like killing of animals and capturing of animals are strictly prohibited.

National Parks: National Parks are meant to protect and preserve flora, fauna, landscapes and historical objects of an area. They not only protect the living organisms, but also the non-living things of that particular area.

Question 4.
What do you mean by Endemic Species? Write about any three species endemic to India.
Answer:
Species of animals and plants comfined to certain specific geographical areas are called endemic species. Following are the three species of animals endemic to India.
(i) Lion-tailed macaque:
This animal got his name from its tail which is 25 cm in length and has a tuft at the end like that of lion’s which is black in colour. It is endemic to south-west India an is one of the most threatened primates.

(ii) Asiatic lion:
Asiatic lion is now endemic to Gir National Patk only as it is believed that the last remnants of this species are found in Gir National Park in Gujarat only.

(iii) Nilgiri ibex:
These stocky goats possessing short coarse fur and a bristly main are endemic to Nilgiri Hills and the Southern postion of the Western Ghats range in Tamil Nadu and Kerela. It is actually called Nilgiri Thar and Nilgiri ibex is its local name.

Question 5.
What is migration and why animals migrate?
Answer:
Movements of animals in large number from one place to another place to escape unfavourable conditions is called migration. Animals migrate for specific purposes. When the purpose is solved, they usually come back to their endemic area.

Migration can be due to unfavourable environmental conditions, eg. The Arctic Tern migrate to Antarctic to spend its winlers. Some birds of colder regions migrate to Asiatic countries during winters. This type of migration is called seasonal migration which occur in many species of insects, birds, marine mammals and herbivorous mammals.

Migration is also done for better food or water availability in other regions due to temperature and other climatic conditions.
Some species of animals and birds also migrate for the purpose of reproduction e.g. fresh watereeds go to saltwaters from freshwater to lay eggs.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

Question 6.
What is poaching? How is it done by anti social elements and for what purpose?
Answer:
Illegal hunting of animals is called poaching. Anti-social element some time create a nexus with the forest staff for poaching; They hunt the animals for selling their skin, horn, fur and hides.

All valuable parts of these animals are used for various purposes and are sold at very high prices.
Uses for ornaments: The bones and other parts like trunks of elephants etc. are used to make ornaments.
Uses in medicines: The horns and bones of some animals like rhinoceros and tigers are used to prepare some traditional medicine specially in Asian countries.
For wall hanging and clothings: The skin, fur and hides are used for the clothing. Mufflers, coats, jackets, skirts etc. are made using leather and fur of the animals like cats, minks, bears foe fur, skin of alligators and snakes and deer and cattle are killed for leather.

Question 7.
Write a short note op migratory birds.
Answer:
Migratory birds are those birds which migrate from their natural habitat to far off areas for breeding. When the natural habitat o.f these birds become very cold, they fly off to distant lands to lay eggs, as climate there is suitable for their breding. They always fly to a specific area every year at a specific period. They migrate in groups to escape the inhospitable climate of their natural habitat.

Birds like Surkhab fly to India from Malyasia. Other birds like Bar Headed Goose, Great Cormorant etc. are also migratory birds.

Question 8.
Recycling of paper helps to protect forest and environment. Explain.
Answer:
Paper is made from trees. Innumerable trees are cut to manufacture paper. If we recycle used paper, we will not have to cut trees to manufacture new paper. Each paper can be recycled 5-7 times and can be used. If we do not throw paper here or there and collect it to be sold to the Kabadiwala, we sire saving our green wealth. It will also save the chemicals used to prepare paper and also the energy used for preparing it. The wastage mid garbage produced during this process will also be reduced and environment will remain clean.

Question 9.
How can we save CHIT green wealth?
Answer:
Our forests are our wealth. We should not destory them but conserve them. To conserve our forests, first of all we should stop cutting them. We should plant as many plants as we cut, so that the number of trees remain unchanged. People should be made aware of the bad effects of deforestation and they should be made familiar with the advantages of the trees for us. Community plantation programmes should be encouraged. Students should be encouraged to plant one plant every year. Plantation of trees is not sufficient. They need proper look after too. So, the tree we plant, should be nourished and taken care of.

Conservation of Plants and Animals Class 8 HBSE Notes

1. A vast variety of plants and animals exist on earth.
2. Deforestation is a threat to the survival of these plants and animals as major varieties of plants and animals are present in forests.
3. Indiscriminate cutting of forests is called deforestation. Land cleared by deforestation is used for other purposes too.
4. Trees cut from these forests are used to make furnitures, papers, houses and is also used as . fuel.
5. Deforestation causes floods, droughts, infertility of soil and many other natural calamities.
6. Soil looses humous due to deforestation and becomes sand, thus deforestation converts a fertile land into a desert and it is called desertification.
7. We should conserve our forests by planting more and more trees which is called afforestation. For conservation of animals; wildlife sancturies and hational parks are formed. They give shelter to our wildlife and help to preserve our endangered species of plants and animals.
8. Variety pf life existing on earth and their inter-relation is called biodiversity. In other words biodiversity is variety of plants and animals and microorganisms generally found in a specific area. Such life is supported by the area called Biosphere.
9. Species ofplants and animals exclusively found in a restricted area are called Endemic species. They are not found in any other geographical area.
10. These species which are at the verge of extinction are called endangered species.
11. Red Data Book contains a record of the endangered species.

HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals Read More »

HBSE 8th Class Science Solutions Chapter 12 Friction

Haryana State Board HBSE 8th Class Science Solutions Chapter 12 Friction Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 12 Friction

HBSE 8th Class Science Friction Textbook Questions and Answers

Question 1.
Fill in the blanks :
(a) Friction opposes the __________ between the surfaces in contact with each other.
(b) Friction depends on the __________ of surfaces.
(c) Friction produces __________.
(d) Sprinkling of powder on the carom board __________ friction.
(e) Sliding friction is __________ than the static friction.
Answer:
(a) relative motion
(b) nature
(c) heat
(d) reduces
(e) less.

Question 2.
Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangement are given below. Choose the correct arrangement:
(a) rolling, static, sliding
(b) rolling, sliding, static
(c) static, sliding, rolling
(d) sliding, static, rolling
Answer:
(c) static, sliding, rolling.

Question 3.
Alida runs her toy ear on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
(a) wet marble floor, dry marble floor, newspaper and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor.
(d) wet marble floor, dry marble floor, towel, newspaper.
Answer:
(a) wet marble floor, dry marble floor, newspaper and towel.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 4.
Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Answer:
Frictional force is acting opposite to the movement of book i.e. upwards.

Question 5.
You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer:
It is difficult to walk on a soapy floor because layer of soap makes floor smooth. The coating of soap reduces the friction and the foot cannot make a proper grip on the floor and it starts getting to slip on the floor.

Question 6.
Explain why sportsmen use shoes with spikes.
Answer:
Sportsmen use shoes with spike to increase the friction so, that their shoes do not slip while they run or play.

Question 7.
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer:
Seema will experience more frictional force because heavy object will be pressed hard against the opposite surface and produces more friction.

Question 8.
Explain why sliding friction less than static friction.
Answer:
Sliding friction is always less than static friction because two sliding objects find less time to get interlocked against, each others, irregularities of surfaces so they get less friction.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 9.
Give examples to show that friction is both a friend and a foe.
Answer:
Friction is a friend because :

  • It allows us to walk comfortably on ground.
  • It allows us to grip and catch different objects.
  • Things don’t move from their places because of friction.
  • Speeds of moving objects can be minimized or stopped by friction only.

Friction is foe because :

  • It causes wear and tear in objects of our daily use and machines we use.
  • Regular maintenance of objects moving against each other (machines and tools) wastes a lot of useful money.
  • It makes the movement of heavy objects very difficult.
  • It does not allow the regular free movement of substances.

Question 10.
Explain why objects moving in fluids must have special shapes.
Answer:
Objects moving in fluids must have a special shape called steamlined shape. Streamlined shape is that shape which overcomes the friction of fluid. They have pointed fronts with little broader middle portion which gets tapered at the back.

Extended Learning – Activities and Projects

Question 1.
What role does friction play in the sport of your choice? Collect some pictures of that sport in action where friction is either supporting it or opposing it. Display these pictures with proper captions on the bulletin board of your classroom.
Answer:
For self attempt.

Question 2.
Imagine that friction suddenly vanishes. How would life be affected. List ten such situations.
Answer:
For self attempt.

Question 3.
Visit a shop which sells sports shoes. Observe the soles of shoes meant for various sports. Describe your observations.
Answer:
For self attempt.

Question 4.
A toy to play with :
Take an empty match box. Take out its tray. Cut a used refill of a ball pen of the same width as the tray as shown in the figure below. Fix the refill with two pins on the top of the tray as shown in Fig. Make two holes on the opposite sides of the tray. Make sure that the holes are large enough to allow a thread to pass through them easily. Take a thread about a metre long and pass it through the holes as shown. Fix beads at the two ends of the thread so that it does not come out. Insert the tray in the outer cover of the matchbox.
Suspend the match box by the thread. Leave the thread loose. The match box will start falling down due to gravity. Tighten the thread now and observe what happens.
Explain your observation. Can you relate it to friction?
HBSE 8th Class Science Solutions Chapter 12 Friction 1
Answer:
For self attempt.

HBSE 7th Class Science Friction Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is friction?
Answer:
Force acting equal and opposite to the relative motion of two objects in contact.

Question 2.
What does the friction depend upon?
Answer:
Nature of object.

Question 3.
Which surface produces more friction?
Answer:
Rough.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 4.
Which surface produces less friction?
Answer:
Smooth.

Question 5.
In which direction does friction work?
Answer:
Opposite to the motion.

Question 6.
What causes-friction between two surfaces?
Answer:
Irregularities of two surfaces.

Question 7.
What happens between irregularities of two surfaces in contact which produce friction?
Answer:
Irregularities get interlocked.

Question 8.
Which surface has large number of irregularities to cause friction?
Answer:
Rough surface.

Question 9.
Between flat and sliding surfaces which surface will cause less friction?
Answer:
Sliding surface.

Question 10.
What causes chalk to write on black board?
Answer:
Friction.

Question 11.
What does friction do to soles of our shoes?
Answer:
It causes wear and tear in soles.

Question 12.
What causes a matchstick to catch fire, when rubbed on rough surface?
Answer:
Friction.

Question 13.
What does friction produce?
Answer:
Heat.

Question 14.
What are things like oils, creams and grease called?
Answer:
Lubricants.

Question 15.
How are the shoes made to counter the friction and make better grip?
Answer:
They have grooves on their soles.

Question 16.
How are athletes and other sports shoes are designed to reduce friction?
Answer:
There soles have nails fixed on them.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 17.
What is done to the tyres of the vehicles to reduce the friction?
Answer:
They are treaded.

Question 18.
What is used in cycle brakes to increase friction?
Answer:
Brake pads.

Question 19.
What does the kabaddi players use to increase friction of their hands to grip their opponents?
Answer:
They rub their hands with soil.

Question 20.
What do we use on carrom board to reduce friction?
Answer:
Talcum powder.

Question 21.
What do we use on the hinges of the door to make door move smoothly?
Answer:
Machine oil/ Oil.

Question 22.
What is avoided between two surfaces to make movement smooth?
Answer:
Interlocking of irregularities.

Question 23.
What is used to reduce friction in machines, where lubrication are not advisable?
Answer:
Oil cushion.

Question 24.
Can we eliminate friction completely?
Answer:
No.

Question 25.
What is used to make heavy luggages move easily?
Answer:
Wheels are attached to their base.

Question 26.
Which friction is applicable when wheels are used to carry heavy weights?
Answer:
Rolling friction.

Question 27.
Among Static, Sliding and Rolling friction which is the smallest?
Answer:
Rolling friction.

Question 28.
How sliding is replaced by rolling in machines?
Answer:
By using ball bearings.

Question 29.
Name any machine, where ball bearing is used to reduce friction.
Answer:
Ceiling fan.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 30.
What is frictional force exerted by liquids called?
Answer:
Drag.

Question 31.
What does frictional force on an object in a fluid depend on?
Answer:
On its speed with respect to the fluid and its shape.

Question 32.
What is the special shape given to objects moving in fluid called?
Answer:
Streamlined shape.

Question 33.
Give three examples of streamlined objects.
Answer:
Ships, boats, aeroplanes.

Question 34.
How is the shape of the body of a fish which helps it in moving in water?
Answer:
It has streamlined shape.

Question 35.
When does rolling friction come in play?
Answer:
When a body rolls on other body.

Short Answer Type Questions

Question 1.
What is friction?
Answer:
Friction is a force which comes in play when two -bodies move on each other. Friction works in opposite direction to the direction of the movement of objects.

Question 2.
What causes friction?
Answer:
Friction occurs when two bodies move on each other. Each surface has some irregularities on it. When two such objects move on each other their irregularities get interlocked and friction arises.

Question 3.
How does the nature of surface effect friction?
Answer:
Nature of the surface plays major role in production of friction. The rough surface produces more friction than the smooth surface. The rough surface has more irregularities on it than the smooth surface, so more force is required to overcome the friction caused by irregularities.

Question 4.
What is a spring balance? How does it work?
Answer:
Spring balance is a device which is used to measure the force acting on a body. It consists of a coiled spring, which is attached to pointer and scale. When some object is hung with it the spring stretches and pointer points to the graduated scale to give the measurement of the force.
HBSE 8th Class Science Solutions Chapter 12 Friction 2

Question 5.
Which friction is less static friction or sliding friction? Why?
Answer:
Sliding friction is lesser than static friction, because in sliding friction the relative motion between two surfaces is less opposed by friction as the irregularities of the two surfaces in contact do not get enough time to interlock with each other which makes the motion easy.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 6.
What would happen, if the floor we walk on, does not produce any friction?
Answer:
If there is no friction on the floor, we would not be able to stand or walk on the floor, because it is the friction which unables us to stand or walk on the surface. The grooves of our feet or shoes get locked into the irregularities of the floor and makes us stand. If friction is not there, then we would simply slip on the floor.

Question 7.
What helps us write with a pen or pencil?
Answer:
It is the friction between the hand and pen or pencil which causes us write with pen. The grooves on our fingers make a grip on the pen’s irregularities and we are able to write.

Question 8.
Why is it difficult to move an object from its static position?
Answer:
When an object is in its static position, it has better hold of the surface on which it is placed. The irregularities of the surface are interlocked properly and more force is needed to overcome the friction offered by interlocking surfaces. So it is difficult to move the object from its position of rest.

Question 9.
Why do we rub our hands in winter when we feel cold?
Answer:
We rub our hands to make them warm, when we feel cold. Rubbing hands against each other cause friction between them. Friction produces heat, this heat makes us warm. We can feel the warmth by touching our hands on our face.

Question 10.
Why do we need to decrease friction?
Answer:
Friction is an evil which causes a lot of wear and tear in objects coming under its effects. It causes a lot of wear in machine parts which rub against each other, it erodes the surfaces and destroy their symmetries. So, we lubricate surfaces to decrease the friction.

Question 11.
How can we increase friction?
Answer:
We need to increase friction of surfaces to control the movement. Friction can be increased by increasing the irregularities of the surfaces in contact. We use spikes in the shoes of the athletes so that they can lock better in the irregularities of the ground to make better grip.

Question 12.
How can we decrease friction?
Answer:
Friction can be decreased by rolling, sliding and lubricating the surfaces in contact. We use ball bearings, wheels and lubricants like oils, grease, cream etc. to decrease the friction. Rolling, sliding and lubricating decrease the irregularities of the surfaces and make them smooth.

Question 13.
What is drag?
Answer:
Drag is the frictional force exerted by fluids. Liquids and gases are collectively called fluids. So the friction caused due to movement of objects in liquids and in air medium is called a drag.

Long Answer Type Questions

Question 1.
What is friction? How do friction arise? Explain.
Answer:
Equal and opposite force exerted by relative motion between two surfaces is called friction. Friction is always exerted in opposite direction to the force exerted. Friction acts between two surfaces. It is caused due to the movement of these two surfaces in contact. Every surface has some irregularities on it. When two surfaces come in contact, these irregularities get locked with each other. When objects are moved, the friction arises in the opposite direction of the movement.

Question 2.
What factors effect the force of friction? Explain.
Answer:
Force of friction depends upon the nature of the surfaces in contact and the force with which these two surfaces are pressed against each other. Nature of the surface on which an object moves, effects the force of friction. Rough surfaces produce more friction, while smooth surfaces produce less friction. Rough surfaces have more irregularities on them so they produce more friction. Smooth surfaces allow easy movement as they have less irregularities and the interlocking of irregularities with other surface is less as compared to the rough surfaces, so they produce less friction.

Secondly, force of friction depends upon how hardly two surfaces are pressed against each other. If two surfaces are pressed hard against each other, then the friction produced will be more.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 3.
How many types of frictions do you know about? Explain.
Answer:
Friction is of different types : Static friction, sliding friction and rolling friction.
Static friction is one which is produced between two surfaces in contact with each at the position of rest. This friction is more powerful than others. It is most difficult to overcome the static friction at this positions, the irregularities are most effectively pressed against each other. This type of friction needs a lot of energy to overcome.

Sliding friction: arises when two objects in contact are in motion. It is lesser than static friction. This friction is lesser because the irregularities of both surfaces do not get enough time to get locked with each other as an object is already in motion.
HBSE 8th Class Science Solutions Chapter 12 Friction 3

Rolling friction: comes in effect when two bodies are rolling on each other. Rolling movement of both objects don’t allow the locking of irregularities, thus it is the smallest friction of all they three types. Drag is the frictional force which is exerted by the fluids on the bodies moving in it. This friction needs a lot of energy to overcome so, bodies of such objects which move in fluids are streamlined to counter the friction offered by fluids.
HBSE 8th Class Science Solutions Chapter 12 Friction 4

Question 4.
What is fluid friction and on what factors does fluid friction depend?
Answer:
Friction exerted by fluids is called fluid friction. Bodies moving in air and liquids bear friction caused by air and liquid. Air and liquids are collectively called fluids. Fluid friction is also called Drag.Drag depends upon the speed of the object with respect to fluid, nature of the fluid and the shape of the object. Slow moving objects face more friction and heavy fluids offer more friction. Objects with pointed front, face less friction. All objects moving in fluids have streamlined shape so as to minimise the friction exerted by fluids.

Streamlined objects have narrow front, broader middle portion and which tapers at the back. All living organisms moving in air and water have streamlined shapes. Birds, fish etc. have streamlined body. So, Aeroplanes, boats, ships etc are designed according to birds and fish, so that they have to face less friction and has to spend less energy to overcome the friction.

Question 5.
prove with the help of an experiment that smoothness of surface reduces friction.
Answer:
Take a pencil or pen. Now put it on a table. Slightly push the pencil and see how much distance it covers, mark the point where the pencil stops after covering the distance. Now take some.cream or oil. Make a small coating of oil on the table or spread polythene on the table if possible. Now again take the pencil and put it at the same initial point. Now push the pencil slightly and let it stop on its own as done earlier. Now mark the point where the pencil stops. See the difference in the distance. In second attempt the pencil has covered more distance. This means it had to face less friction in second attempt. It proves that smoothness of the surface reduces friction.

Question 6.
Why and how do we increase friction?
Answer:
We increase friction deliberately to control the movements and motion of the objects. We also increase the friction for better grip and hold. Friction can be increased by making surfaces coarse and pressing two surfaces harder. Coarse surface has more irregularities to grip irregularities of other surface better, thus making the things come to a halt and give a better grip if object is stationary. We use brake pads in vehicles. When brake pads are pressed by pressing the lever, it gets pressed against the tyres and arrest the movement of the tyres and with this the vehicle comes to stop.

Pens are provided with ridges at the point where we hold them for writing, so that the friction between fingers and pen becomes more and a better grip can be made to write fluently. Pens without ridges get slipped out from our hands easily.

HBSE 8th Class Science Solutions Chapter 12 Friction

Question 7.
Why and how do we decrease friction?
Answer:
We decrease friction to save the objects from wear and tear. Friction causes wear and tear on the surfaces of the objects. It causes damage to the objects specially machines and machine parts. So, we apply a film of oil or grease between the surfaces in contact, so that it produces less friction and it causes no damage to the parts. Oils, grease etc. are called lubricants, which are used to make surfaces smooth and minimise friction. In most of the cases rolling of objects is used to reduce friction. Ball bearings are used in cycles, vehicles and machines because it reduces friction. Wheels are used to move heavy objects because wheels roll on the ground thus reducing friction and this makes the dragging of heavy objects easy. Tyres carry heavy and loaded trucks on them, as they produce less friction and need lesser energy to move them.

Friction Class 8 HBSE Notes

1. Friction is the force equal and opposite to the relative motion between two surfaces in contact.

2. Force of friction acts on both the surfaces in contact.

3. There are many factors which affect friction :

  • It depends on the nature of surface.
  • It depends on smoothness of surface.
  • It depends on the hardness with which two surfaces in contact are pressed against each other.

4. Friction has no relation with area exposed to force of friction.

5. Friction is static, when it opposes the force applied on the body.

6. When two surfaces slide on each other, sliding friction comes into play.

7. Sliding friction is less than the static friction.

8. Friction is an evil which causes a lot of wear and tear on the surfaces of the objects due to opposite forces in action.

9. Wear and tear is more in case of static friction and less in case of sliding friction.

10. Friction is an evil but a necessary evil. No body would have been able to walk on the floor, if friction was not in play :

11. When two surfaces roll on each other the rolling friction is applied, for example in case of wheels under attache-cases. Rolling reduces the friction and movement becomes easy and smooth.

12. Fluids also exert force of friction and reduce the speed. To avoid friction due to fluid, bodies of objects moving in fluids have pointed and streamlined fronts and bodies.

13. Aeroplanes and ships etc. have streamlined bodies to over come the friction caused by air and liquids.

HBSE 8th Class Science Solutions Chapter 12 Friction Read More »

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Haryana State Board HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 1 Crop Production and Management

HBSE 8th Class Science Crop Production and Management Textbook Questions and Answers

Question 1.
Select the correct word from the following list and fill in the blanks:
Float, water, crop, nutrients, preparation
(a) The same kind of plants grown and cultivated on a large scale at a place is called …………… .
(b) The first step before growing crops is …………… of the soil.
(c) Damaged seeds would …………… on top of the water.
(d) For growing of crop, sufficient sunlight and …………… and …………… from the soil are essential.
Answer:
(a) Crop
(b) preparation
(c) float
(d) water, nutrients.

Question 2.
Match items in column ‘A’ with those in column ‘B’:

(A)(B)
(i) Kharif crops(a) Food for cattle
(ii) Rabi crops(b) Urea and super phosphate
(iii) Chemical fertilisers(c) Animal excreta, cow dung, urine and plant waste
(iv) Organic manure(d) Wheat, gram, pea
(e) Paddy and maize

Answer:

(A)(B)
(i) Kharif crops(e) Paddy and maize
(ii) Rabi crops(d) Wheat, gram, pea
(iii) Chemical fertilisers(b) Urea and super phosphate
(iv) Organic manure(c) Animal excreta, cow dung, urine and plant waste

Question 3.
Give two examples of each:
(a) Kharif Crop
(b) Rabi Crop
Answer:
(a) Paddy and maize
(b) Wheat and gram

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 4.
Write a paragraph in your own words on each of’the following:
(a) Preparation of soil (b) Sowing (c) Weeding (d) Threshing.
Answer:
(a) Preparation of Soil:
Soil is prepared to sow the seeds. It is tilled to loosen the soil particles for better absorption of water and manures. Loosening of soil particles add humus and nutrition to the soil for better crops. Tilling of soil is done by using ploughs which are pulled by bulls. Tractor driven cultivators are also used to till the soil.

(b) Sowing:
Sowing means implanting the seeds in the prepared soil. Seeds are first selected. Better and healthy breeds of seeds are selected. They are then sowed in the fields with the help of seed drills and funnel shaped tools. The funnel, has a long body on one end of which is placed in soil. Seeds are put in the funnel and seeds go into the soil through long pipe which is carried over in the field with help of ploughs, the lower end pierces through the soil, spreading the seeds. Some seeds are simply spread through the field by hand. Some saplings are planted directly in the field manually.

(c) Weeding:
Unwanted plants growing along the crop are called the weeds. These weeds absorb the nutrients from the soil which are ment for the crops. They are, therefore, removed from the fields. Weeds are either removed manually or by mechanical tools. Certain chemicals are also used to kill the unwanted plants growing in the crops.

(d) Threshing:
Separation of grains from the chaff is called threshing. Seeds are removed from the chaff by threshers. When the crop is harvested, it is cut alongwith the stalks. They are then separated and the grains are removed. This whole process takes place with the help of a huge machine called combine.

Question 5.
Explain how fertilisers are different from manure.
Answer:
Differences between fertilizers and manure:
(i) Fertilisers are chemical substances, while the manures are the organic substances.
(ii) Fertilisers are prepared in the factories while the manures are prepared in fields.
(iii) Fertilisers don’t provide any humus to soil while manures provide a lot of humus.
(iv) Fertilisers are rich in plant nutrients will manures are less rich in plant nutrients.

Question 6.
What is irrigation? Describe two methods of irrigation which conserve water.
Answer:
Watering the crops in the fields is called irrigation. Irrigation is done at different intervals. Irrigation should be done in a way in which water does not get wasted, two such methods which conserve water are:
(i) Sprinklers:
Sprinklers work like fountains. Long perpendicular pipes have holes at regular distances, when water is supplied, it comes out of these holes and spray water in field. These holes have rotating nozzles which sprinkle water in all directions. Limited outflow of water, controls wastage of water.

(ii) Drip System:
This system allows the water to flow drop by drop at the roots of the plants. It contains a main pipe which have further lateral pipes containing small nozzles for the outflow of the water. Nozzles are such placed that they throw water at the roots of the plants, which saves water from flowing around uselessly.

Question 7.
If wheat is sown in kharif season, what would happen? Discuss.
Answer:
If wheat are grown in Kharif season, they would not grow as they do not need ihuch water to grow. The seeds would get destroyed in excess water due to rainy season.

Question 8.
Explain how soil get affected by the continuous plantation of crops in a field.
Answer:
Continuous plantation of crops drains off the nutrients of the soil. It leaves the land unfertile and unable to bear crop. It does not give any time to the soil to replenish the absorbed nutrients by the crops, thus unable to sustain any further healthy and good crop.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 9.
What are weeds V How can we control them?
Answer:
Weeds are the unwanted plants growing along crops. They share the nutrients meant for plants and thus are harmful. We can control weeds with the help of chemicals called weedicides. Weeds are the unwanted plants growing along the main crops. They are either removed manually or by chemicals. Weedicides are sprayed in the fields to kill the unwanted plants. These weedicides do not affect the main crop. Weeds are removed or killed during their vegetative phase before flowering or bearing seeds.

Question 10.
Arrange the following boxes in proper order to make a flow chart of sugarcane crop production:
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-1
Answer:
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-2

Question 11.
Complete the following word puzzle with the help of clues given below:
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-3

Down
1. Providing water to the crops.
2. Crop grains have to be kept for a long time in proper conditions.
5. Certain plants of the same kind grown on a large scale.

Across
3. A machine used for cutting the taatured crops.
4. A rabi crop that is also one of the pulses.
6. A process of separating the grain from chaff.
Answer:
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-4

Activity 1.3

FoodSources
1. MilkCow, Buffalo, She-goat, She-camel
2. Cereals grainsPlants like wheat, rice
3. MeatGoat, Cow, Hen, Fish
4. VegetablesPlants like brinjal, potatoes, tomatoes, etc.

Extended Learning – Activity And Projects

Question 1.
Sow some seeds in the soil and arrange to water them by drip irrigation. Observe daily.
(i) Do you think it can save water?
(ii) Note the changes in the seed.
Answer:
(i) Yes, drip irrigation saves water as it doe not allow the water to flow on sides and get wasted.
(ii) Seeds slowly get germinated.

Question 2.
Collect different types of seeds and put them in small bags. Attach these bags in a herbarium file and label them.
Answer:
Do it yourself.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 3.
Collect new agricultural machine pictures and paste in a file with their names and uses.
Answer:
Tractor to drew ploughs and carriage combines for threshing.
Plough for tilling soil.
Winnowing machine for removing chaff.

4. Project Work: Visit a farm, nursery or a garden nearby. Gather information about:
(i) importance of seed selection
(ii) method of irrigation
(iii) effect of extreme cold and extreme hot wather on the plants
(iv) effect of continuous rain on the plants
(v) fertilisers / manure used.
Answer:
(i) Good seed give good crops.
(ii) Traditional and modern
(a) Traditional: Moat, Chain pumps, Dhekli and Rahat
(b) Modern: Drip irrigation and Sprinklers.
(iii) Extreme cold and heat destroy the crops.
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-5
(iv) → Continuous rain get plants decomposedand waer logged in fields.
→ Minerals and fertilisers get flown away.
→ Top fertile layers get destroyed.
(v) Enhance the productivity of soil.

For more information, visit:

  • www.krishiworld.com / html / balanced fertiliser.htm.
  • www.ikis.com / links / ap.cultivation.html.

HBSE 8th Class Science Crop Production and Management Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Why do every living organism need food?
Answer:
Every living organism needs food to grow and perform various other activities and body functions.

Question 2.
Where do we get our food from?
Answer:
We get our food from plants and animals.

Question 3.
What is agriculture?
Answer:
Growing and managing crops is called agriculture.

Question 4.
What is crop?
Answer:
When same type of plants are grown at a large scale, it is called crop.

Question 5.
Name the factors controlling crop production.
Answer:
Soil, water, sunlight and air.

Question 6.
What are the rainy season crops called?
Answer:
Kharif crops.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 7.
What are the summer season crops called?
Answer:
Zayed crops.

Question 8.
What are the winter season crops called?
Answer:
Rabi crops.

Question 9.
Name any three Kharif crops.
Answer:
Paddy, maize, cotton.

Question 10.
Name any three Rabi crops.
Answer:
Wheat, gram, mustard.

Question 11.
Name any three Zayed crops.
Answer:
Moong, musk melon, bitter gourd.

Question 12.
What is tilling?
Answer:
Tilling is the loosening and turning of the soil.

Question 13.
What are crumbs?
Answer:
Crumbs are big pieces of soil present in fields, which require tilling.

Question 14.
Which agricultural tools are Used for tilling?
Answer:
Plough, hoe and cultivators.

Question 15.
Name tools used for sowing.
Answer:
Funnel shaped pipe with plough and seed drill.

Q. 16.
What is transplantation of seeds?
Answer:
Small saplings of plants are directly plantedj in fields. This is called transplantation.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 17.
What are fertilizers and manures?
Answer:
Manures and fertilizers are the substances added to soil to enhance its fertility and nutrients.

Question 18.
Which manure is called organic manure?
Answer:
Manure obtained from the dead bodies of plants and animals.

Question 19.
Name any two important fertilizers.
Answer:
Urea, NPK (Nitrogen, Phosphorus, Potassium).

Question 20.
What is a fallow?
Answer:
An uncultivated field between two croppings is called a fallow.

Question 21.
Write sources of irrigation.
Answer:
Wells, tubewells, ponds, lakes, rivers, dams and canals.

Question 22.
What is harvesting?
Answer:
Cutting of the crop after it is mature is called harvesting.

Question 23.
What is threshing?
Answer:
Separating seeds from the chaff is called threshing.

Short Answer Type Questions

Question 1.
What do you mean by agriculture?
Answer:
The term agriculture is derived from the Latin words ‘Ager’ which means field and ‘culture’ which means cultivation. Thus, cultivation in fields means agriculture.

Question 2.
Write the names of various agricultural practices undertaken to produce a crop.
Answer:
Following agricultural practices are performed to produce the crop:
1. Soil preparation
2. Sowing
3. Adding manure and fertilizers
4. Irrigation
5. Protection from weeds
6. Harvesting
7. Storage.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 3.
How many categories of crops are sown in India based on the seasons?
Answer:
Three categories of crops are sown in India based on the seasons:
(i) Kharif crops are sown during rains.
(ii) Rabi crops are sown during winters, and
(iii) Zayed crops are grown during summers.

Question 4.
Why is the $oil turned and loosened before seeds are sown?
Answer:
The soil is turned and loosened during the process of ploughing. The ploughing loosens the soil particles and turn the soil of upper
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-6
surface. This allows the nutrients from the dead organism to be released back in the soil and better penetration and absorption of nutrients by plant roots.

Question 5.
What are manures and fertilizers?
Answer:
Manures and fertilizers are used to enhance the productivity and fertility of the field. Manure is made of waste products of animals and plants. Fertilizers are chemicals rich in nitrogen, potassium.

Question 6.
What is the role of water in production of crops?
Answer:
Water is essential for all plants. Crops should get enough water at different stages of their growth. Different crops require different amount of water in the field. The wheat crop requires moderate amount of water at the time of sowing, flowering and ripening of crop.
Therefore, corps should be irrigated properly according to their needs.

Question 7.
What are the different methods of irrigation?
Answer:
Different methods of irrigation are adopted according to the requirement of soil and size of the field. Some common methods of water supply are through small channels, which get water from tubewells and canals, lift irrigation, sprinkler, dripping irrigation, etc.
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-7

Question 8.
Define weeding. What tools are used for weeding?
Answer:
Weeds are unwanted and undesirable plants which grow alongwith the crop plants in the field. They grow rapidly than the crop plants and cause harm to them. It is, therefore, essential to remove weeds at proper time. The process of removing the weed plants is called weeding. It is done either by hand or by khurpi. It is also done by spraying chemicals or weedicides.

Question 9.
What is humus? How is it formed?
Answer:
Humus is a kind of soil rich in nutrients. It is formed by the microbial action on dead decaying bodies and leaves. It is generally formed on those spots where-there are dense layers of trees. The soil below it becomes dark having more number of pathogenic bacteria.

Question 10.
What are pesticides?
Answer:
The chemicals which are used to protect crops from the organisms called pests are known as pesticides. They are used to kill eggs and larvae of insects who could cause harm to the crops. Pesticides are sprayed in the fields by different methods at different intervals.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 11.
What safety measures are to be taken in handling pesticides and weedicides?
Answer:
Insecticides and pesticides are highly poisonous chemicals. They kill the pests. They can harm the humans also. So, certain precautionary measures should be taken while spraying pesticides and weedicides.

They should be kept away from the reach of children.
They should not be inhaled while spraying. Gloves and mouth covers should be used while spraying them.
Hands should be washed properly after their use.

Question 12.
Distinguish between pesticides and weedicides?
Answer:
Weeds are controlled by using certain chemicals called weedicides. These chemicals do not cause any damage to the crop.
Pesticides are the chemicals which are used to kill the pests growing on the crops. They kill the eggs and larvae of the insects.

Question 13.
Explain the process of harvesting?
Answer:
The removal of crop after maturity is called harvesting. The harvesting is done manually with the help of ordinary sickles in crops like wheat, paddy and maize. Even tractor driven machines are also used for harvesting wheat and paddy. Fruits and vegetables are plucked manually.

Question 14.
Explain the process of threshing,
Answer:
The crops need to be threshed to separate grains from the chaff. The mechanical harvesters help in both threshing and separating the grains. The small farmers thresh their crops by spreading the crops on the ground and walking of animals over it. Now-a-days threshing is done by threshing machines driven by tractors or electric motors, which separate grain from chaffs.

Question 15.
What factors influence the crop production?
Answer:
The factors that influence the crop production are as follow:
(i) “Soil: It is the upper layer of earth’s crust. It is the natural medium which supports plant growth.
(ii) Water: Plants require water during various stages of their growth and development such as germination, flowering, ripening, etc.
(iii) Air: Air is essential for breathing and photosynthesis.
(iv) Sunlight: It is essential for plants as a major promotion factor for photosynthesis, germination and flowering.

Question 16.
Suggest ways for the improvement of crops.
Answer:
Following ways should be adopted to improve the crops:
(i) Use of improved seeds.
(ii) Improve fertility of soil.
(iii) Protection against pests and weeds.
(iv) Better transport and storage facility.
(v) Introduction of high yielding varieties of seeds.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Long Answer Type Questions

Question 1.
What are some basic principles of crop production?
Answer:
There are certain conditions which are very important for causing the good crop yield. Good and right kind of soil, seeds, water and protection of crops from weeds and pests as well as the use of proper implements and practices- all go to determine the quality and reliability of crop yield.

A field or farm needs to be managed properly in order to get better yield. Farmers, therefore, must observe some important things which are listed below:
(i) The crop field should be open so that sunlight and air are abundantly available.
(ii) The field should be protected from stray cattle and tresspass which may destroy the crop.
(iii) The soil should be loosened and turned before sowing so that the plant roots can penetrate into it easily and are well ventilated. The latter helps in holding the plant firmly. Root and tuber crop plants need loosened soil for proper growth of the plant product.
(iv) The right amount of water should be available neither too less nor too in excess.
(v) The soil should contain sufficient nutrients for the growth of the plants.
(vi) The unwanted plants such as weeds should be removed from the soil. These weeds compete with the main plants and deprive them of their nourishment.

Question 2.
What is the use of soil for the plants?
Answer:
Soil plays an important role in agriculture in following ways:
(i) Soil fix up the plant in the soil. It holds the roots firmly and anchor the plant.
(ii) Soil has the power of retaining the water which helps the absorption by plants. It also contains minerals etc. which provides food nutrients to the plants.
(iii) It also provides space for living to useful animals such as earthworms which turn up soil and make it fertile.
(iv) Soil holds air in its gaps. This air is used by the plant for its respiration as well as for the respiration of the useful plants and bactria.

Question 3.
How are pests controlled in a crop field?
Answer:
Pests are the organisms smaller bugs which damage the crop plants in the field, during transportation, in the godowns. The common pests are birds, rats and other rodents, some animals, insects and micro-organisms belonging to different groups. They are harmful as they destroy the crop. Pests like locusts, beetles, red spiders, aphids, etc. can be controlled by three methods.
(i) Chemical control: The use of pesticides like DDT, malathion, BHC and aldrin. These chemicals are quick and effective way of controlling the growth of the pests.
(ii) Biological control: One insect feeds von other insect. In this method harmless insects are introduced in the field which will be harmful for insects and other pests.
(iii) Growing pests resistant varieties: Breeding crop varieties which are resistant to pests is a very effective and common method of pest control.

Question 4.
Why do we irrigate our crops? Explain.
Answer:
Water is required by the plants for the following activities:
(i) The seeds sown in the soil absorb water for various activities related to germination, such as activation of phenul, radicle and embryonal axis.
(ii) Water is essential for softening of soil particles so that the roots may penetrate deeply into the soil easily.
(iii) The mineral salts, manure particles, etc. dissolve in water and make the dilute solution. It is easily absorbed by the root hair.
(iv) Water is essential to maintain the turgidity of the cells and to keep them inactive form.
(v) Water is evaporated from the soil as well as from the aerial parts of the plants. Irrigation is essential to fill up the loss of water.
(vi) For the preparation of food by the plants through the process of photosynthesis, water is very essential.

Question 5.
Why an earthworm is called a friend of a farmer?
Answer:
Before sowing seeds every farmer prepares his soil for sowing. He digs the soil. He does tilling with help of tractors and ploughs. This all is done to loosen the soil particles so that air .and nutrients can be easily absorbed. Earthworm is an organism which lives under the soil and make burrows for itself. This burrowing action loosens the soil for better penetration of roots of the crops.
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-8
It create channels through the field which improves the physical properties of the soil. The burrowing action of earthworm improves soil structure, helps in formation of humus mix and till the soil and increase the supply of nutrients of the plants.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Question 6.
Write a short note of thresting and winnowing.
Answer:
When a farmer cut his crops, he has to separate the grains from the crop it is done in two ways. Manually and with machines.
HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management-9
The separation of seed from the crops by beating out the seeds (grain) from the crop is called threshing. It is done manually or by using threshers with combines.

After separating the grain from the harvested crop, it is required to separate grain from chaff. This process is done by winnowing. The grains are thrown from the height in the direction of air. The air carries away the lighter chaff or dried stems and leaves and the heavier grains drop down in form of a heap. This whole process is called winnowing.

HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management

Crop Production and Management Class 8 HBSE Notes

1. All living beings need food to live and perform various other activity.
2. We get food from plants and animals. The plant food is grown in fields making use of various processes. This is called agriculture.
3. All plants of same types grown together are called crops. Different types of crops are grown in the fields e.g. cereals (wheat, paddy rices) fruits and vegetables, etc.
4. Based on seasons many crops are grown. Rainy season crops are called Kharif. Winter crops are called Rabi and Summer crops are called Zayed crops.
5. To grow a crop a number of activities has to be performed. These are called agricultural practices. These agricultural practices include: soil preparation, sowing, adding manure and fertilizers, irrigation, protection from weeds, harvesting, storage, etc.
6. Preparation of soil includes loosening soil. This is called tilling or ploughing. Plough, cultivator and hoe are used as tools.
7. Sowing means putting the seeds in the loosened ground to grow.
8. For a healthy and good crop manure and fertilizers are added to the crop. These are chemicals which enhance the crop production.
9. When we grow crop in the field it takes all the nutrition away from the soil. This nutrition is – required for the next crop. The soil is replenished with nutrition by these fertilizers and manures. Crop-rotation is another method of replenishing nutrition in soil.
10. Crops are watered sufficiently by canals, drips and rainwater. This is called irrigation of crops. Irrigation is the most important process of crop production.
11. Undesirable plants growing among the crops are removed manually or by machines. These unwanted plants are called weeds, chemicals used to kill weeds are Called weedicides.
12. Sometimes some small animals start eating the crops. These are called pests. Special chemicals
are sprayed on the crops to kill the pests. These chemicals are called pesticides.
13. After the crops are ready, they are harvested. Grains are separated from the chaff. This process is called threshing. Threshers are used to do this process.
14. The harvested grains are then Stored in huge stores, after they are properly dried in sun. These stores kre called granaries.
15. We also get our food from animals. For this purpose some useful animals are domesticated
and reared. This is called Animal Husbandry. Animals like cows, buffaloes, goats, hens etc. are domesticated for food.

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