Question

E. Long Answer Type Questions


1. Describe an activity to show that mixing of vinegar and baking powder is a chemical change.

2. How can you say that burning of a substance is an irreversible change?

3. Encircle the odd one out and give reasons for your choices.
(a) Souring of milk, inflating a balloon, cooking of food, burning of coal

(b) Making of ice cubes, melting of butter, frying of potatoes, heating of water

4. How would you show that chemical changes are irreversible?​

Answer 1

Explanation:

Describe an activity to show that mixing of vinegar and baking powder is a chemical change.

2. How can you say that burning of a substance is an irreversible change?

3. Encircle the odd one out and give reasons for your choices.

(a) Souring of milk, inflating a balloon, cooking of food, burning of coal

(b) Making of ice cubes, melting of butter, frying of potatoes, heating of water

4. How would you show that chemical changes are irreversible

Answer 2

Explanation:

1. take 5ml of vinegar in a beaker. Add a spataful of baking powder to it. A hissing sound is produced and carbon dioxide gases envolved,which is the new substance formed in the process. this shows that mixing of vinegar and baking powder is a chemical change.
2. Burning of a substance is an irreversible change.We can prove it by an example of burning of paper.When we burn a paper,it changes into ash and smoke is produced.We can not get back the paper from the ash and smoke.So,we can say that burning of a substance is an irreversible change.
3. a) inflating a balloon is different reason- inflating a balloon is a physical change as only size of the balloon changes other all are chemical changes.

• b) frying of potatoes is different reason-it is a chemical change as we can not get back the raw potatoes after frying.other all are physical changes.
• 4. we can show that chemical changes are irreversible by following activity--------____same as answer number 1