Question

Give a reason for the following observations;
a) Naphthalene balls disappear with time without leaving any solid.
b) Water kept in an earthen pot becomes cool during summer.

Answer 1

1. Naphthalene balls are sublime, aka when bought to a condition where a normal solid should change to liquid, it skips the process and instantly changes into vapour.
2. A earthern pot has micropores, which water seeps into. The water on the micropores displaces heat energy from the water inside the pot, and via latent heat of vaporisation, cools the water to the point where it can be compared to fridge water.

Answer 2

1. napthalene balls sublime when exposed to air . They directly change into the gaseous state without changing into the liquid state.

2.Water kept in an earthen pot becomes cool during summer , this is so because an earthen pot has micropores . Water seeps out through these micropores taking heat energy form the water inside the pot and using it as latent heat of vaporisation and hence the water cools down.


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