This lake has frozen over due to the cold weather. As liquid water freezes, its molecules gain/lose thermal energy. How does the motion of the water molecules changes during freezing

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Physics

Tristian Pratt

27 September, 05:57

This lake has frozen over due to the cold weather. As liquid water freezes, its molecules gain/lose thermal energy. How does the motion of the water molecules changes during freezing

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Cynthia Fitzgerald · Answer 1

I know that during melting, there is no temperature change as the heat energy is used to do work against potential bond energy but why doesn't temperature change when freezing?

Freezing is the opposite process of melting. If the temperature does not increase as the ice melts, the temperature will not decrease as water freezes.

Melting and freezing are entropy changes. Entropy measure the amount of disorder in a system. A system, like ice, which has less freedom of motion, has less disorder. A system, like liquid water, which has more freedom of motion, has more disorder.

So water has more entropy than ice.

Ice is a very ordered arrangement of H2O molecules in a crystalline form. As heat energy is added to ice, the energy is used the break the bonds between the H2O molecules in the ice crystals. So, the temperature remains constant. You might say that the energy that is added to the ice is used to increase the entropy of the system, instead of increasing the temperature of the system.