Solute, solvent and solution

You've probably taken ORS (Oral Rehydration Solution) when you were ill. It keeps the body from drying out, and you learnt to make it at home in Grade 6: sugar and salt stirred into water.

Why does every sip of ORS taste the same, never salty in one sip and sweet in the next? Because the sugar and salt spread evenly all through the water.

Now stir chalk powder, sand or sawdust into water. They don't spread evenly: you can see them, and they settle. Those are non-uniform mixtures.

A uniform mixture, such as salt or sugar in water, is called a solution.

When a solid dissolves in a liquid, the solid is the solute and the liquid is the solvent. The solute dissolves in the solvent to make the solution.

Solute + Solvent → Solution

When two liquids make a solution, it's not always clear which is dissolving which. Then the one there is less of is called the solute, and the one there is more of is the solvent.

A neat exception: the chashni of gulab jamun is a lot of sugar in a little water. Even so, water is the solvent and sugar the solute. The smaller-amount rule is only for two liquids; a solid dissolved in a liquid is always the solute, however much of it there is. It's the job that decides, not the amount.