Practical section 0.4 : cooling

 Here is how we approached 0.4 in the aspect of cooling.

index can be found here

We use a ice and salt solution to generate a mixture below Zero, and use it to see when ice formation starts in pure water.

We used.

Pure water
Sodium Chloride
Thermometer
Beakers
Timers
Test tubes and clamps for holding them

So, what happens?

Sodim Chloride lowers the freezing point of water. That is why lakes tend to freeze faster than sea water in winter here in Denmark.

so, when we add salt into a mixture of ice and water, the freezing point of the mixture decreases and the ice begins to melt. In order for a phase change to occur, the ice draws the heat of fusion from its surroundings, which allows the temperature to decrease. 

This draws heat away from the pure water in our test tube as well, and we see formation of ice chrystals,

Using a mixture of sodium chloide and ice was a way to make ice cream in the days before electrical freezers, and ice was stored in special ice houses for that reason (and for other cooling uses as well)

Here is a shorter version of the experiment: