Question:

Which of the following is not an example of a chemical change?
a) Burning of coal
b) Melting of ice
c) Rusting of iron
d) Digestion of food

Answer:

The correct answer is option 'B', which says "Melting of ice" is not an example of a chemical change.

Explanation:

Chemical changes are the changes that involve the breaking and forming of chemical bonds between atoms and molecules. In these changes, the substance is transformed into a new substance with different properties. On the other hand, physical changes are the changes that do not involve any chemical reaction and the substance retains its chemical properties.

Let us discuss each option given in the question to understand which of them is an example of a chemical change.

a) Burning of coal:
When coal is burnt, it reacts with oxygen in air to produce carbon dioxide, water vapor, and other gases. This is a chemical change as the coal is transformed into a new substance with different properties.

b) Melting of ice:
Melting of ice is a physical change as it does not involve any chemical reaction. When ice melts, it changes from a solid state to a liquid state, but the chemical properties of water remain the same.

c) Rusting of iron:
Rusting of iron is a chemical change as it involves the reaction of iron with oxygen and water to form hydrated iron oxide or rust. The properties of iron change during this process.

d) Digestion of food:
Digestion of food is also a chemical change as it involves the breakdown of complex molecules into simpler molecules with the help of enzymes. The chemical properties of food change during this process.

Therefore, option 'B' which says "Melting of ice" is not an example of a chemical change is the correct answer.