Endothermic reaction

I think most of you have heard of what is endothermic reaction. It is a chemical reaction when heat is taken in and end up the container that contain the chemical will be very cold.

Today this experiment is to show that when 2 chemical react the endothermic reaction can actually freeze a thin film of water on the wooden block and then the beaker can actually stick onto the wooden block.

This experiment is very easy. All you need is Barium hydroxide (app 2-4g) and Ammonium thiocyanate (app 2-4g). Mix both together with a bit of deionised water soon (ard 1min), you can see that the film of water actually freeze and stick on the beaker. (definately is not surface tension as we tried to push the block slightly, it still will not drop).

We tried subsituite Barium hydroxide with Calcium hydroxide but it will not work even though you can feel the coldness around the beaker. So try it out yourself if you do not believe it.