Haryana State Board HBSE 6th Class Science Solutions Chapter 6 Changes Around Us Textbook Exercise Questions and Answers.
Haryana Board 6th Class Science Solutions Chapter 6 Changes Around Us
HBSE 6th Class Science Changes Around Us Textbook Questions and Answers
Exercises
Question 1.
To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Answer:
Yes, this change can be reversed.
Question 2.
You accidently dropped your favourate toy and broke it. This is a change, you did not want. Can this change be reversed?
Answer:
No, this change can not be reversed.
Question 3.
Somethings are listed in the following table. For each change write in blank column. Whether the change can be reversed or not.
| S. No. Change | Can be reversed (Yes/No) |
| 1. The sawing of a piece of wood | |
| 2. The melting of ice candy. | |
| 3. Dissolving sugar in water. | |
| 4. The cooking of food. | |
| 5. The ripening of a mango. | |
| 6. Souring of milk. |
Answer:
(1) Can be reversed; Yes.
(2) No.
(3) Yes.
(4) No.
(5) No.
(6) No.
Question 4.
A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Answer:
No, we cannot reverse this change.
Question 5.
Give examples to explain the difference between changes that can or cannot be reversed.
Answer:
A change that can be reversed is called a reversed change. For example, blowing of a balloon, making aeroplane from a piece of paper by folding it and making ball from a dough etc. changes can be reversed. A change that cannot be reversed is called irreversible change. For example: Ripening of fruits, burning of paper and cooking of food, etc. cannot be reversed.
Question 6.
A thick coating of a paste of plaster of paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed.
Answer:
No, the change cannot be reversed.
Question 7.
A bag of cement lying in the open gets wet due to rain during the night. The next day the sunshines brightly. Do you think the changes, which have occured in the cement, could be reversed?
Answer:
No, the change cannot be reversed.
HBSE 6th Class Science Changes Around Us Important Questions and Answers
Very Short Answer Type Questions
Question 1.
What type of change is of climate change?
Answer:
Periodic change.
Question 2.
Can deforestation be considered as a reversible change?
Answer:
No, it is not a reversible change.
Question 3.
Can you obtain wood from saw dust?
Answer:
No, we cannot reverse this change.
Question 5.
Give examples to explain the difference between changes that can or cannot be reversed.
Answer:
- Heart beat
- Phases of moon
- Swinging of the pendulum of a clock
- high and low tide in sea every day.
Question 6.
Pickling of mango is a desirable change. How?
Answer:
Pickling of mango is always a desirable change, because we pickle mango according to our taste and desire.
Question 7.
Give an example of natural change.
Answer:
Germination of seed.
Question 8.
Give an example of irreversible change.
Answer:
Burning of paper.
Question 9.
What is a physical change?
Answer:
Change in which no new product is formed.
Question 10.
What is a chemical change?
Answer:
A change in which a new substance with different properties is formed.
Question 11.
Mention two undesirable change.
Answer:
- Breaking of glass ware
- flooding of rivers.
Question 12.
Give four examples of desirable change.
Answer:
- Turning of milk into curd
- Formation of manure from animal dung
- Cleaning of utensils
- Change of season.
Question 13.
What is pasteurisation?
Answer:
Heating and cooking of milk is known as pasteurisation.
Question 14.
State two advantages of non¬periodic change.
Answer:
- Growth of plants and animals and boiling of milk.
- Washing of cloth are some advantages of non-periodic change.
Question 15.
What is solution?
Answer:
When salt is added in water, it dissolves in water to form solution which has properties that mixed to form it.
Short Answer Type Questions
Question 1.
Can deforestation be considered as a reversible change?
Answer:
Deforestation is not a reversible change because it cannot take place in reverse direction. Forest cannot be grown quickly.
Question 2.
Give four examples of non-periodic change.
Answer:
- Occurring of earthquake
- Falling of ripening fruits from tree
- Landslides
- Train accident.
Question 3.
Is burning always a desirable change?
Answer:
Burning is always not a desirable change. It causes pollution, which is not a desirable change. Burning of house is not a desirable change, because they are harmful to us.
Question 4.
What is the advantage of pasteurising milk?
Answer:
Milk is an essential commodity. Some harmful bacteria spoil it after some time. In pasteurisation, microbes are killed and milk is prevented from spoiling for several days and can be stored without refrigeration.
Question 5.
Explosion of a cracker is a chemical change. Explain.
Answer:
When we burn a cracker, it exploide. Heat, light and smoke comes out after explosion. Many new products are formed. So it is a chemical change.
Question 6.
Most physical changes are reversible. Give reasons with two examples.
Answer:
All physical changes are reversible. Because in physical changes, no new product is formed. They can be reversed easily.
Examples:
(i) Dissolving of sugar in water is a physical change and we get back sugar and water easily.
(ii) Formation of ice from water. In melting of ice, we can get water back.
Question 7.
Identify the type of change and state whether energy is evolved or absorbed in each one of the following:
Burning of a candle, lighting of a bulb, preparation of food by green plants, volcanic eruption.
Answer:
- Burning of a candle : Chemical change, energy evolved.
- Lighting of a bulb : Physical change, energy evolved.
- Preparation of food by green plants: Chemical change, energy absorbed.
- Volcanic eruption: Chemical change, energy evolved.
Question 8.
Define the term ‘interaction’.
Answer:
When two or more substances act on each other, as a result a change may take place. This is called interaction.
Question 9.
What are the differences between chemical and physical changes?
Answer:
Difference between chemical and physical changes:
| Chemical change | Physical change |
| 1. A new substance is formed. | 1. No new substance is formed. |
| 2. It is a permanent change. | 2. It is a temporary change. |
| 3. The composition of new substances changes. | 3. No change in the composition of change takes place. |
| 4. It is irreversible. | 4. It is reversible. |
| 5. Heat/light evolved or absorbed during change. | 5. No heat light evolved or absorbed or may be evolved or absorbed. |
Question 10.
Name two similarities between the various objects in your surroundings.
Answer:
- Each object occupies space indicated by its size and shape.
- Objects are made up of materials and some are made up of combination of materials.
- The structural units of objects are called cells and molecules respectively.
Question 11.
How do you group the objects into two main categories?
Answer:
Objects can be grouped on the basis of shape, size and colour. Objects can be categorised into living and non-living objects.
- Living objects such as plants and animals.
- Non-living objects such as stone, table, chair, etc.
Living organisms show movement, respiration, excretion, breathinbg, nutrition, reproduction and sensitivity towards heat, light, sound and touch etc.
Question 12.
Why do animals and plants respire?
Answer:
All living things perform various kinds of activities. Animals move and run around. You go to school and play. For these activities energy is required. This energy living beings obtain through the process of respiration. The oxygen is used to produce energy from the food which organisms consume. Oxygen burns the food and release energy. This energy is utilised for various activities. This can be represented as follows :
Question 13.
How is the process of photosynthesis in plants helpful to the animals?
Answer:
Plants prepare their own food by the process of photosynthesis in green leaves and plants. They prepare food in green leaves in presence of sunlight with the help of carbon dioxide and water. The food prepared by plants, all animals depend for their food on plants. In this way, photosynthesis is helpful to animals.
Long Answer Type Questions
Question 1.
State the reason for each of the following :
(i) Ripening of a fruit is a chemical change.
(ii) Rotation of fan is a periodic change.
(iii) Cooked food is stored in refrigerator.
(iv) Iron sheet is coated with tin before making a can.
Answer:
(i) Ripening of fruits is a chemical change because after ripening, a new product with different properties is formed.
(ii) The rotation of fan is a periodic change, because the change occurs after a fixed interval of time.
(iii) Cooked food is spoiled by bacteria and microbes. To prevent food from spoiling, it is stored in refrigerator, where microbes are killed due to low temperature.
(iv) Iron sheet is coated with tin before making can, because tin coated sheets do not rust. It prevents iron sheet from rusting.
Question 2.
When is a change said to have taken place in a material? Explain with the help of an example.
Answer:
We have many things around us. All these things have certain properties such as state (solid, liquid or gas), position, shape, size, colour, temperature, composition and structure, etc. When one or more properties of a thing become different, we say that it has changed or a change has taken place. Changes involve different kinds of alternations in the things around us. When a change takes place, there may be a change in the state, position, shape,, size, colour, temperature, composition or structure of the material of the object. When ice melts, it forms water. Ice is a solid, whereas water is a liquid. So, the melting of ice involves a change in state (form solid to liquid state).
Question 3.
What is meant by reversible changes and irreversible changes? Explain with examples.
Answer:
Reversible change: A change which can be reversed to form the original substance is called a reversible change.
Example:
When we heat ice, it melts to form liquid water. A change from solid to liquid takes place during the melting of ice. Now, if we cool the water by keeping in the freezer of a refrigerator, it again changes into solid ice. So, the change from ice to water, by heating, has been reversed by cooling. Thus, the melting of ice to form water is reversible change.
Irreversible change : A change which cannot be reversed to form the original substance or substances is called irreversible change.
Example : If we burn a piece of paper, it changes into ash and smoke. Now, we cannot combine the ash and smoke to form the original piece of paper. So, the burning of paper is a change which cannot be reversed. Therefore, the burning of paper is an irreversible change.
Question 4.
Explain why, the burning of paper is said to be an irreversible change whereas the boiling of water is known as reversible change.
Answer:
If we burn a piece of paper, it changes into ash and smoke. Now, we cannot combine the ash and smoke to form the original piece of paper. So, the burning of paper is a change which cannot be reversed. Hence, the burning of paper is an irreversible change. When we boil water by heating, then it changes into steam. Now, if we cool the steam, then water is formed again. So, the changing of water into steam has been reversed by cooling. Thus, the boiling of water is a reversible change.
Changes Around Us Class 6 HBSE Notes
1. We can bring about a change in a substance by heating, applying forces or by mixing it with something else.
2. When a solid mix with water to form a solution and we can say that the solid has dissolved,
3. Different solids dissolve to different degrees in the same amount of water. On heating, amount of solid that can dissolve increases.
4. A change can be physical or chemical. In chemical change, a new product is formed. A physical change can reverse.
5. Slow changes : The changes that takes place over a long period of time, like hours, days, months and years is called slow change. Example : Change during growth and formation of manure.
6. Desirable changes : Changes which are useful to us such as formation of curd from milk and formation of manure from cow dung.
7. Undesirable changes: The changes which are not useful to us are called undesirable changes. Examples : Breaking of glass tumbler and spoiling of food stuffs.
8. Fast changes : Those changes which occur within a short time interval. Example : Burning of a matchstick.
9. Periodic change : A change which occurs during a definite time interval is called periodic change. Examples : Heart beat, phases of moon etc.
10. Non-periodic change: A change which does not repeat again and again after a regular interval of time. Examples : Earthquake and train accidents.
11. Reversible change : If a change can be reversed, it is called reversible change; stretching of rubber band.
12. Irreversible change : A change which cannot be reversed. Example : Burning of paper, etc.
13. Physical change : It is a temporary change in which no new substance is formed. Example : Switching of electric heater. Dissolution of sugar in water.
14. Chemical change: It is a permanent change in which an entirely hew substance is formed with different properties. It is an irreversible change.
Example: Cooking of food and formation of curd from milk.
15. There are a variety of objects found in the surroundings. The objects have a variety of shapes and size. Shape and size of each object indicate the space it occupies.
16. Objects observed around us in spite of variety in shape and size are made up of matter. Some are categorised as living while others are non-living.
17. All living things need food to carry out various activities. Food provides energy for various functions.
18. Green plants prepare their own food by using water and minerals (from soil) carbon dioxide (from air) and sunlight with the help of green pigments. Unlike plants, animals take food in the form of plants/animal products.
19. The living things may be autotrophs or heterotrophs depending upon their mode of feedings.
20. Animals do breathing and respiration. In plant respiration involves direct exchanges of gases between air and cells. Non-living objects do not carry out respirations.
21. Respiration is a process which involves exchanges of gases like oxygen and carbon dioxide.
22. All living things remove wastes like carbon dioxide, water and other salts. Animals remove wastes through excretory organs.
23. Plants secrete wastes as gum, resin, latex. Non-living objects like stone, chair etc. do not remove wastes.
24. When living things increase in size utilizing energy, it is called growth. They grow for a certain period called life span and show growth for a limiting period.
25. Plants keeps growing throughout their lives. Some trees grow for hundred of years. Non-living things do not show the process of growth.
26. Living things show response to stimuli through factors like water, light, gravity, touch etc; while non-living things do not show such mechanism of responding to stimuli.
27. All living organisms produce their own kind, as mango will produce mango, cat will produce cat and man will produce man.
28. Reproduction in living organisms is multiplication of organism and non-living organism like stone and chair do not reproduce.
29. Living organisms show movements and locomotion. All living being are made up of basic functional units called cells.