Question

Select the correct answer from the choices A, B, C, and D which are given. Write only the letter corresponding to the correct answer.

Jaya wants to experiment with sugar cubes. Which of the following causes a sugar cube to only change physically, not chemically.

• A. Burning the sugar cube with a match
• B. Dehydrating the sugar cube with sulphuric acid
• C. Crushing the sugar cube and dissolving it in water
• D. Chewing the sugar cube and digesting it.

Answer 1

The correct option is C

Crushing the sugar cube and dissolving it in water

Explanation for correct option:

Option C

Physical change:

• A physical change is a change in which no new substance is formed.
• A physical change is temporary and reversible.
• In physical change the chemical composition of the original substance is not altered.
• For example, drying of wet clothes, breaking of a glass tumbler, drying paints, etc.
• When we crush a sugar cube, we only change its physical appearance.
• When we dissolve it in water, its particles get into the spaces between the water particles.
• No new substance is formed and there is no chemical reaction happening. Hence, it is a physical change.

Therefore, option C is correct.

Explanation for incorrect option:

Option A

Chemical change:

• A chemical change is a permanent change in which new substances are formed.
• The chemical change is permanent and cannot be reversed by a simple physical method.
• A chemical change involves an exchange of energy in the form of heat or light.
• For example, rusting of iron, burning of wood, respiration, etc.
• When we burn a sugar cube, the chemical composition of sugar changes, and sugar reacts with oxygen to form new substances including smoke.
• Hence, it is a chemical change.

Therefore, option A is incorrect.

Option B

• When we treat sugar cube with sulphuric acid, it reacts with sulphuric acid and forms carbon, a black solid-liquid mixture.
• During this process a chemical reaction occurs and new substances are formed.
• Hence, it is a chemical change.

Therefore, option B is incorrect.

Option D

• When we chew a sugar cube, saliva, and other enzymes are secreted which break it down into simpler substances.
• Further, when it is digested, many liquids are secreted which digest, that is breaks it into very simple forms.
• So, after digestion, a new substance is formed. So, this is also a chemical change.

Therefore, option D is incorrect.