Question

char baar yeh question post kar chuka hoon koi toh ans dedo

1. You forget a toast in toaster and it turns black. Can this change be reversed?

2. You blow dry your wet hair, How can you reverse this change?

3. Why is cooking of food an irreversible change?

4 Give an example of a physical change that cannot be reversed.

5. What kind of change is observed when copper utensils appear to be greenish in
colour?

6 Which of these changes can be reversed: grain to flour, bud to flower, melting of
ghee and ripening of fruits?

7 Define the following:
a. Reversible change
b. Physical change
c. Irreversible change
d. Chemical change
G. Answer the following questions in detail.

1. Explain with the help of examples, the difference between the changes that can be
reversed and those that cannot be reversed.

2. Explain the type of changes involved in this sequence
lce cube placed in sun —— puddle of water — disappearance of puddle

3. What are physical changes? Give two examples.

4. Why is getting a new hair cut considered to be a physical change?

5 What do you observe when fireworks explode? Is anything new formed? What type
of change is it?

6. Squeezing oranges for juice is a physical change. Justify.

7 Why does the idli batter rise when kept overnight without refrigeration?

8. Places such as the mountains, where temperatures get very low during winters, the
plastic pipes meant for water transportation break. Why do you think it happens?

9. Differentiate between:
a, reversible and irreversible changes
b. physical and chemical changes
c evaporation and condensation
d. expansion and contraction

10. Look at the following pictures and write down as to whether the changes are
reversible or irreversible. For reversible changes, draw a second arrow below the
first in the opposite direction.​​

Answer 1

Answer:

1.no

2. yes

3.When we heat raw food materials, we get cooked food. The cooked food cannot be converted back into raw food. So, the cooking of food is an irreversible change. this is a chemical change .

4.use an egg in our recipe, we need to crack it open. This is a physical change because the egg is now in two parts, but the egg did not transform into a chicken, or into any other substance for that matter; it is still an egg. If we were to take our wooden spoon and grind it down to sawdust, we could see another example of physical change. The spoon would change form, but it would still be wood.

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Answer 2

1. no
2. by making our hair wet
3. bcoz a new substance is formed
4. grinding wood into saw dust
5. chemical change
6. melting of ghee
7. a. change which can be reversed is called reversible change.

b. Change which affect only physical properties of a metal

c. change which can't be reversed

d. change which affect chemical properties of a metal