CBSE Class 6 Science Changes Around Us Assignment

Class-VI
L-6 Changes Around Us

Question 1. Can you change the shape of paper by folding?
Answer: Yes, we can change the shape of a piece of paper by folding it, such as making a paper boat or a paper aeroplane.
In simple words: Folding paper changes its shape temporarily without destroying the paper.

Exam Tip: Folding paper is a classic example of a physical and reversible change.

Question 2. Can all changes always be reversed?
Answer: No, not all changes can be reversed. Some changes are permanent and cannot be undone.
In simple words: Only some changes can be reversed back to their original state, while others result in new substances.

Exam Tip: Distinguish between reversible changes (like melting ice) and irreversible changes (like burning wood or cooking food).

Question 3. List five changes which can be reversed.
Answer:
i) Folding a piece of paper
ii) Melting of ice into water
iii) Inflation of a balloon
iv) Dissolving salt in water
v) Stretching a rubber band
In simple words: Reversible changes are those where the original substance can be recovered easily.

Exam Tip: Always list simple physical changes when asked for examples of reversible changes.

Question 4. List five changes which cannot be reversed.
Answer:
i) Burning of paper or wood
ii) Cooking of food (e.g., baking a roti)
iii) Ripening of fruits
iv) Curdling of milk
v) Growth of a plant from a seed
In simple words: Irreversible changes form new substances and cannot be changed back to the original form.

Exam Tip: Chemical changes or permanent alterations are generally irreversible.

Question 5. Define Evaporation?
Answer: Evaporation is the process by which a liquid turns into a gas or vapor when heated or exposed to air. For example, water changes into water vapor on heating.
In simple words: The process of liquid turning into gas is called evaporation.

Exam Tip: Mention both the phase change (liquid to gas) and the role of heat for complete marks.

Question 6. What is melting?
Answer: Melting is the process by which a solid changes into a liquid on heating. For example, ice melts into water when kept at room temperature or heated.
In simple words: Solid turning into liquid upon heating is melting.

Question 7. Write True or False against each statement:
i. Change occur in boiled egg can be reversed. 
Answer: False
ii. Change in position of stretched rubber band can be reversed. 
Answer: True
iii. Melting of ice cream is reversible change. 
Answer: True
iv. Curding of milk can be reversed. 
Answer: False
In simple words: Boiling an egg or curdling milk changes the substance permanently, while stretching rubber or melting ice cream can be undone.

Exam Tip: Read each statement carefully to identify if a new permanent substance is formed.

Question 8. State whether the following changes can be or cannot be reversed:
i) Making folded aeroplane from paper
Answer: Can be reversed
ii) Baking of roti on tawa
Answer: Can not be reversed
iii) Burning of candle
Answer: Can not be reversed (Note: Melting of the wax part of a candle is reversible, but burning the wick and gas production is irreversible; overall burning is classified as irreversible).
iv) Melting of wax.
Answer: Can be reversed
In simple words: Paper folding and wax melting can be undone, but baked roti and burning candles cannot be turned back to their original state.

Exam Tip: Be careful with candle burning questions - melting wax is reversible, but burning the wick is irreversible.