Question

Saw whether changes are physical, chemical, reversible or irreversible changes

1. Evaporation of alcohol
2. Expansion of air
3. Melting of butter on toast
4. Cooling a mixture of air and kerosene vapours
5. Decomposition of organic matter
6. Burning of a sparkler
7. Pulling copper into a thin wire
8. Mixing solid sulphur and iron fillings
9. Chewing of food
10. Photosynthesis
11. Digestion of food
12. Burning a mixture of air and kerosene
13. Cutting vegetables
14. Cloud formation in the sky
15. Burning of wood
16. Tarnishing jewellery

Answer 1

A physical change is where only the state of matter is changed and no chemical reaction takes place and no new product is formed.
A chemical change is such where a new substance is formed by a chemical reaction.

1. Evaporation of alcohol- physical change, reversible
2. Evaporation of alcohol - physical change, reversible
3. Melting of butter on toast - physical change, irreversible
4. Cooling a mixture of air and kerosene vapours​ - physical change, reversible
5. Decomposition of organic matter - chemical change, irreversible
6. Burning of a sparkler- chemical change, irreversible
7. Pulling copper into a thin wire - physical change, reversible
8. Mixing solid sulphur and iron fillings - physical change, reversible
9. Chewing of food - chemical change, irreversible
10. Photosynthesis - chemical change, irreversible
11. Digestion of food - chemical change, irreversible
12. Burning a mixture of air and kerosene - chemical change, irreversible
13. Cutting vegetables - physical change, irreversible
14. Cloud formation in the sky - physical change, reversible
15. Burning of wood - chemical change, irreversible
16. Tarnishing jewellery - chemical change, reversible