A glass is half full of water, and the level is marked…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A glass is half full of water, and the level is marked. A spoon of sugar is dissolved in the water, and the level is marked again. It has hardly risen.
- Explain what happened to the sugar.
- The same is tried with a spoon of fine sand. Would the level rise? Why is it different?
Need a reminder? The key ideaShow
Matter is made of particles that are far too small to see. There are spaces between them, which is why sugar can dissolve in water with no rise in the level, and why a gas can be squeezed.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Sugar dissolves: it breaks up into its particles, and these go into the spaces between the particles of water. They spread through the water, so they add almost nothing to the volume.
Step 2. (b) Sand does not dissolve. Each grain stays whole and sinks to the bottom, and a grain is far too big to fit into the spaces between the particles of water. So the grains push the water up, and the level rises.
Answer: (a) The sugar particles fit into the spaces between the water particles. (b) Yes: sand does not dissolve, so it takes up its own space.
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