Question

A thermometer shows a certain temperature on its scale. When its bulb is covered with a piece of cloth, soaked in spirit, it is observed that the reading of the thermometer decreases. Give reason for this observation.

Answer 1

1. Spirit is a volatile liquid, i.e., it evaporates very quickly at normal temperature and pressure.
2. When the thermometer bulb is covered with a spirit socked cloth the spirit from the cloth start to evaporate.
3. The spirit takes the latent heat from evaporation from the thermometer bulb.
4. As a result, the thermometer loses heat and the reading on the thermometer scale decreases.