Question

Before the doctor gives an injection, he applies spirit at that spot. At that time our skin feels very cool because:

• A. the spirit evaporates using the heat from our body.
• B. the spirit kills the bacteria present on the skin.
• C. the spirit is at low temperature.
• D. the spirit loses its heat when it is taken out of the bottle.

Answer 1

The correct option is A the spirit evaporates using the heat from our body.

Evaporation occurs when particles or molecules escape from the liquid and turn into vapours. Evaporation is a surface phenomenon.
During evaporation, heat energy is absorbed from the surrounding particles, lowering the temperature.
On application of spirit, its molecules evaporates from the surface of our skin absorbing heat from it.
Hence, when a doctor applies spirit our skin feels very cool.