When you put salt on ice, it lowers the melting point. How does this work?

Question

I did a phase change demo where i had to put salt on ice and watch the ice melt at a lower temp. Now I would like to know why. How does this work?

Answer 1

When you add salt to water, you introduce dissolved foreign particles into the water. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. For a solution of table salt (sodium chloride, NaCl) in water, this temperature is -21°C (-6°F) under controlled lab conditions.

Decrease of free energy of salt due to decrease in temperature is less than the corresponding decrease for water.

So, when salt is mixed in water, the free energy of the system decreases less with decrease in temperature than it would have decreased if water were present alone. As a result, the free energy for the corresponding solid state (to be formed if the mixture freezes) becomes lower than the free energy of pure water only at a relatively lower temperature. That is why the melting (or freezing) point decreases.


JUST CHECK THIS OUT:
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-salt-melts-ice.shtml

it's so much fun haha.
and it explains it pretty well.

Answer 2

Salt helps ice melts faster

Answer 3

The ions in the salt interfere with the formation of the crystals of ice by binding to the molecules of water, forming a solution that requires lower temperatures to slow the molecular vibration to the point that lower molecular attraction can form crystals.

Answer 4

it jz does