Question

Identify the physical change:
A. Photosynthesis
B. respiration
C. Digestion of food
D. Melting of wax

Answer 1

Hint: In physical change, the physical properties of the substance changes like color, state, shape. In physical change formation of new products does not take place and the composition remains the same.

Complete step by step answer:
A physical change is defined as the change where no new substance is formed. In physical change, the composition of the substance remains the same but the rearrangement of the molecule can be changed. The physical change is temporary. In physical change only physical properties of the substance like shape, size, colour are affected.
The photosynthesis is the process used by plants to produce their food. In this process light energy is converted into chemical energy. The chemical reaction which takes place in photosynthesis process involves reaction between six mole of carbon dioxide and six mole of water to form one mole of glucose and six mole of oxygen. As a new product is formed in this process, therefore photosynthesis is a chemical change.
In the respiration process, the glucose available in the body undergoes an oxidation reaction to form carbon dioxide and water along with energy. As the composition is changed and a new product is formed, therefore respiration is a chemical change.
During the digestion process, the enzymes present in the stomach help to break down the food particles into simpler one. Thus, digestion is a chemical change.
In melting of wax the solid wax changes to liquid wax. As the state of the wax is changed, therefore melting of wax is a physical change.

So, the correct answer is Option D.

Note: When we burn a candle, physical and chemical change both takes place. When the candle is burned the solid wax melts down which is a physical change and the wax present near the flame burns to release carbon dioxide and heat which is a chemical change.