Question

Which of the following are chemical changes?
A. growth of a plant
B. rusting of iron
C. mixing of iron filings and sand
D. cooking of food
E. digestion of food
F. freezing of water
G. burning of a candle

Answer 1

Hint: As we know that in a chemical change, a product is formed from the combination of two substances. It is found that chemical reactions are also irreversible except by further chemical reactions.

Complete step by step answer:
A. growth of a plant- It is basically an irreversible change. It is found that photosynthesis is a chemical change process that involves formation of new products. Hence, we can say that it is a chemical process.
B. rusting of iron- It is basically an irreversible process, that involves formation of new products. Hence, we can say that it is a chemical process.
C. mixing of iron filings and sand- It is basically a reversible process, as by using a magnet these can be easily separated.
D. cooking of food- It is basically an irreversible process, where some reactions take place that form a different product. Hence, we can say that it is a chemical process.
E. digestion of food- we can say that it is a chemical change, as digestion of food produces different reactants.
F. freezing of water- It is basically a reversible process, as it is a physical change. For example ice can be melted to get water.
G. burning of a candle- we can say that it is a chemical change, as it is found that wax is made up of hydrocarbons that melts and becomes a gas. It is also found that the hydrocarbons are broken.
So the correct answer is “A, B, D and G”:

Note: - We should note that the physical changes are exactly opposite to that of chemical changes. As we know that they are basically reversible changes without involvement of energy.