The chapter Changes Around Us introduces students to the different types of changes that occur in our surroundings. It explains how some changes can be reversed, while others cannot. Through everyday examples like melting of ice, cooking food, and breaking objects, students learn about reversible and irreversible changes.
The chapter helps to categorize changes based on factors such as heating, cooling, applying force, or mixing substances. It emphasizes that while some changes are temporary, others are permanent, providing a fundamental understanding of physical and chemical processes in nature.
Learning Objectives
By the end of this chapter, students will be able to:
Changes Around Us Questions and Answers
Explore ‘Changes Around Us’ Class 6 Science with questions and answers. Learn about reversible and irreversible changes through simple explanations and examples—the perfect study guide for BOSEM students.
Textbook Exercise Changes around us
Q1. To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Ans: Yes, this change can be reversed by unfolding the dress again.
Q2. You accidentally drop your favourite toy by breaking it. This is a change you did not want. Can this change be reversed?
Ans: No, this change cannot be reversed.
Q3. Some changes are listed in the following table. For each change, write in the blank column whether the change can be reversed or not.
Ans:
| Change | Can be reversed (Yes/No) |
|---|---|
| Sawing of a piece of wood | No |
| Melting of ice candy | Yes |
| Dissolving Sugar in water | Yes |
| Cooking food | No |
| Ripening of mango | No |
| Souring of milk | No |
Q4. A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Ans: It depends on what type of materials is used to draw the picture. If the pencil is used to draw the picture then the change can be reversed by erasing the drawing with an eraser. If pen or colours are used to draw the picture then the change cannot be reversed.
Q5. Give examples to explain the differences between changes that can or cannot be reversed.
Ans:
| Change that can be reversed | Change that cannot be reversed |
|---|---|
| Melting of ice cube | Sawing of a piece of wood |
| Dissolving sugar in water | Cooking food |
| Inflation of balloon | Ripening of mango |
| To roll out a roti from a dough | Milk changes into curd |
| Making aeroplane by folding paper | Burning or incense sticks or wood |
| Stretching of rubber band | Making paper toys by cutting the paper |
| Drawing a picture with a pencil | Growth of living beings |
Q6. A thick coating of plaster of Paris (POP) paste is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be reversed?
Ans: No, the change in Plaster of Paris cannot be reversed.
Q7. A bag of cement lying in the open gets wet due to rain during the night. The next day, the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Ans: The changes cannot be reversed because the cement that hardened up after getting wet cannot be obtained back to its original state.
Changes around us Notes
- Many changes are taking place around us. some changes occur naturally on their own while some are induced by humans.
- Changed may be in shape, position, size, height, colour, state, internal composition etc.
For example Inflation of balloons, from a seed growing to a new plant, flowers bloom and then wither away, we grow taller leaves colour change, ice melts into water, incense sticks change into ash and smoke when burned etc. - Types of change
Reversible changes: Reversible changes mean the changes which can be reversed back into their original form. For example: Making a toy aeroplane by folding paper, inflation of balloon etc.
Irreversible changes: These are permanent changes that cannot be reversed. Examples: burning an incense stick, cooking food, etc. - Substances change their form by heating cooling or by mixing two or more substances together.
Examples
a. The water changes into water vapour when heated. (Evaporation)
b. Water vapour changes into liquid when cooled. (Condensation)
c. Ice melts into water when heated. (Melting)
d. Dissolving sugar into water.
Changes Around Us Extra Questions
Q1: What is the difference between reversible and irreversible changes?
Answer: Reversible changes can be undone, like melting ice or folding clothes. Irreversible changes cannot be undone, such as burning paper or cooking food.
Q2: Can you reverse the formation of curd from milk? Why?
Answer: No, the formation of curd from milk is an irreversible change because once the milk turns into curd, it cannot be turned back into milk.
Q3: Why is breaking a toy an irreversible change?
Answer: Breaking a toy is an irreversible change because once it is broken, it cannot be restored to its original form.
Q4: What are fast and slow changes? Give examples.
Answer: Fast changes happen quickly, like the bursting of a balloon, while slow changes take time, like the rusting of iron.
Q5: Is dissolving sugar in water a reversible change?
Answer: Yes, dissolving sugar in water is a reversible change because the sugar can be recovered by evaporating the water.
Q6: Can we obtain wood from sawdust? Why or why not?
Answer: No, we cannot obtain wood from sawdust because it is an irreversible change. Once wood is turned into sawdust, the process cannot be reversed to form solid wood again.
Q7: Is ironing clothes a reversible change? Explain.
Answer: Yes, ironing is a reversible change because wrinkles can reappear on clothes after they are worn or washed. The process of removing wrinkles can be repeated as needed.
Q8: Give two examples each of reversible and irreversible changes.
Answer: Reversible changes: Melting of ice, dissolving sugar in water.
Irreversible changes: Burning of paper, breaking a glass.
Q9: How is the growth of a plant an irreversible change?
Answer: The growth of a plant is an irreversible change because once a seed grows into a plant, it cannot return to its seed form. The biological process is permanent.
Q10: What are the different ways to bring about a change?
Answer: Changes can be brought about by heating, cooling, mixing substances, or applying force. For example, heating can melt ice, while applying force can break an object.
Q11: Is folding paper a reversible change? Why?
Answer: Yes, folding paper is a reversible change because the paper can be unfolded and restored to its original shape. No new substance is formed during this process.
Q12: Why is the burning of a candle an irreversible change?
Answer: The burning of a candle is an irreversible change because the wax is transformed into carbon dioxide and water vapour, and it cannot be changed back into a candle again.
Q13: How does the formation of clouds show reversible changes?
Answer: The formation of clouds is a reversible change because it involves the phase transformation of water. Water evaporates into vapour (a gas), rises into the air, and condenses back into liquid in the form of droplets to create clouds. This process can reverse when these droplets fall as rain, returning to their original liquid form.
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