Some substances dissolve when you mix them with water. When a substance dissolves, it looks like it disappears. But in fact it has just mixed with the water to make a transparent (see-through) liquid called a solution.
Dissolving happens when the solute breaks down into tiny particles that fit in between the gaps of the solvent particles.
When you mix sugar (the solute) with water (the solvent), the sugar dissolves to make a transparent solution. Salt dissolves in water too.
Heat can help some substances dissolve faster in water. Salt, for example, will dissolve quicker in hot water than in cold water.
At some point, the solvent (the liquid doing the dissolving) won’t be able to take any more of the solute (the solid being dissolved). This means that the solution is saturated.
Substances that dissolve in water are called soluble substances.
Substances that do not dissolve in water are called insoluble substances.
When you mix sand or flour with water, they do not dissolve.