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HCS (Haryana)Prelims2022General Studies
Question
Following are some processes involving changes of state: 1. Evaporation of water 2. Burning of candle 3. Dissolution of sugar in water 4. Electrolysis of water to form hydrogen and oxygen Select the correct Option
Options
- A 2, 3 and 4 involve chemical change only
- B 1, 2 and 3 involve physical change only
- C Only 1 is a physical change
- D 2 involves both physical and chemical change
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Correct Answer
D 2 involves both physical and chemical change
Model Answer
Burning of candle
- Physical Changes in Burning Candle include Candle wax turning into liquid wax when heated and because it turns back into solid wax when it cools. Changes like this can be reversed.
- Chemical Changes in Burning Candle new substances such as carbon monoxide, carbon soot, water vapours, heat, and light during the process of evaporation. This is a change that can't be undone.
Dissolution of sugar in water
- Since the dissolution would not necessitate the creation of something new, it is a physical change rather than a chemical one.
- When you dissolve sugar in water, you get nothing more or less than a "sugary" solution.
- Electrolysis of water to form hydrogen and oxygen:
- Because you are separating the water into its components, hydrogen and oxygen, it undergoes a chemical transformation and ceases to be water.
- 2H2O (l) → 2H2(g) + O2(g)
Evaporation of water
- The chemical composition of a liquid does not change when it evaporates. As a result, evaporation, which transforms a liquid into a gas, is a physical change.