Physics
(a) Which contains more heat, 1 kg water at 100°C or 1 kg steam at 100°C?
(b) Name a substance that contracts on melting and expands on solidification.
(c) In cold countries, juice bottles are placed underwater, so as to avoid freezing. Why?
Answer
(a) 1 kg of steam at 100°C contains more heat than 1 kg of water at the same temperature. This is because the heat energy in the steam includes the additional latent heat of vaporization, which is the energy required to change water from liquid to vapor at its boiling point.
(b) Ice contracts on melting and expands on solidification.
(c) The reason for keeping juice bottles underwater is that water due to it's high specific heat capacity can impart a large amount of heat before reaching to it's freezing point. Hence, bottles kept in water remain warm and do not freeze when there is considerable fall in surrounding's temperature.
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