# Solutions for temperature reduction

We measure with a thermometer temperature of water. Prepare solutions for temperature reduction:

1) from 120 g of ammonium nitrate in 200 ml of water and 2) with 60 g of ammonium chloride in 200 ml of water in glass beakers.

Let's drop thermometers and thermoscopes into the solutions for lowering the temperature, which will show a sharp drop in temperature. Let us immerse the test tubes with 1-2 ml of water. After a few minutes, the water in the test tubes will freeze. Solutions have such temperatures: the first from -13 to -13,6 degrees Celsius, and the second -13,3 degrees Celsius.

Each liquid freezes at a certain temperature. But in solutions, the presence of a dissolved substance lowers the temperature of the solvent, and the stronger, the more concentrated the solution. In most cases, only the solvent crystallizes out of the solution upon freezing, as a result of which the concentration of the solution increases during freezing. This results in an even lower freezing point. Thus, the solution freezes not at a certain temperature, but in a certain temperature range. The difference between the freezing temperatures of a pure solvent and a solution is called a decrease in the freezing point of the solution. The lowering of the freezing point also explains the fact why salt is thrown over it, usually calcium chloride CaCl2. Dissolution of calcium chloride is an exothermic process, as a result of which a large amount of heat is released, therefore, dissolving, calcium chloride contributes to the melting of ice.