Question

Which of the following is a physical change?
A.Rusting of iron
B.The burning of coal
C.Cooking food
D.Converting ice into water

Answer 1

To answer this question, you must recall changes in which the substance does not undergo a change in composition. Changes that are reversible and change only the physical appearance are known as physical changes. Chemical changes are usually irreversible changes.

Complete step by step solution:
We know that there are two types of changes that generally occur in matter, namely physical changes and chemical changes.
Physical changes are the changes that take place when a substance is boiled, melted, condensed or precipitated and only the physical properties of the substance are affected. Chemical changes generally involve chemical reactions.
Using the definitions above, we can now classify the given options as physical or chemical changes.
Option A involves the rusting of iron. Rusting involves the oxidation of iron by air or by the oxygen present in air. It is known as aerial oxidation. It involves a change in the chemical composition of the substance and thus is a reversible change.
Option B is the burning of coal. We can clearly say that the combustion of a substance with oxygen is a chemical reaction and thus we can say that combustibility is a chemical property. So the burning of coal is a chemical change.
Option C is cooking food. We know that once cooked, food cannot be uncooked. Its chemical composition changes and it is irreversible. Thus cooking food is a chemical change.
Option D is converting ice to water. There is no change in the chemical composition of water. The process is reversible and ice can be obtained back by freezing. Thus it is clear that it is a physical change.

The correct option is D.

Note: We can easily find the answer to this question just by using the fact that chemical changes are reaction which involve the formation and breakage of bonds and are irreversible unlike physical changes which are reversible.