2. Add 5 g of sugar and measure the new mass. 3. Explain what happened. Was mass conserved? 4. Repeat the experiment using a graduated cylinder. This time measure the volume of the water before and after adding a measured volume of sugar.
5. Explain what happened. Was volume conserved? Soluble
substances are able to dissolve
in a liquid.
In the above activity, sugar and water are mixed together to form a solution. It is not possible to see the sugar molecules once they are in solution. Substances like sugar that dissolve in water are called soluble substances. The diagram in Fig. 1 shows how this happens. The lump of sugar separates into tiny molecules and these molecules spread out between the water molecules. It is no longer possible to see the sugar molecules as they are too small to be seen individually.
Water Sugar Sugar dissolved in water
Single sugar molecules are too small to see
Fig. 1 How sugar dissolves in water. An insoluble
substance does not dissolve in a liquid.
Fig. 2. shows sand and water mixing. The sand particles cannot fill the gaps between the water molecules so they do not dissolve. Instead they settle to the bottom of the container. Sand is insoluble in water.
Water Sand Solvent The liquid in
which a substance dissolves.
Fig. 2 Sand is insoluble in water. Solute
A substance that dissolves in a liquid.
Solution
A mixture of a solute and a solvent.
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We call the part of a solution that does the dissolving (usually a liquid) the solvent. We call the part that dissolves (usually a solid) the solute. A solution is a mixture of a solute and a solvent.
Solvent Solute Solution Fig. 3 A solution of sugar in water. Solute Solvent
