Dissolves sugar glass in water

Pure sugar - water rises?

Does the water level actually change when sugar and / or salt are dissolved in water?

We made the following experiment for this:

We filled two water glasses about 2/3 full with water and recorded the water level with a marker. We put a heaped tablespoon of rice grains in one glass and the same amount of sugar in the other. The children already knew that rice does not dissolve in water. The rice was only used as a comparison.

As expected, the sugar and rice sank to the bottom of the appropriate glass. The water level in both glasses has risen, it was well above the mark.

The sugar glass was then stirred diligently so that the sugar dissolved quickly. Attention was paid to the change in the water level. And indeed, it seemed as if the water level in the sugar glass had decreased a bit when it was loosened.

Things that drown in water displace water upwards. This means that the water level is rising. In fact, just as much water is displaced as the object occupies space. In our case, this meant displacing a heaping tablespoon of water at a time.

The peculiarity of sugar is that it dissolves in water.

The following happens when loosening: Many small water particles wrap themselves like a coat around tiny sugar particles and thus loosen them. So the sugar hasn't gone away and it still needs its place. In a solution, however, water and sugar particles are so cleverly arranged that they actually take up a little less space. That's why the water level really drops a little when loosening.

Overall, the particles in a solution are closer together than in pure tap water. A solution is therefore denser than tap water. A nice experiment on this subject is "salt water is denser".

We tried the following variant: One size Amount of sugar cubes and coarse salt crystals were each poured into a 2/3 full glass of water. We recorded the water level "before and after"!

The goal was to dissolve salt and sugar in the water. We tried to accelerate the dissolution process by stirring. But the salt in particular took hours to dissolve. We were able to observe how the water level that had risen at first slowly decreased and then at the end clearly perceptible was below the black line.