Structure and Properties of Matter
Solutes, solvents and solutions
Name the solute and the solvent in a solution, tell a saturated solution from an unsaturated one, and say how temperature changes what will dissolve.
Stir sugar and salt into a glass of water and each sip tastes the same as the last — not salty at one moment and sweet the next. The two solids have not settled into layers or corners; they have spread evenly through the whole of the water. Stir in chalk powder instead and you get something quite different, with the powder plainly visible and drifting down.
Three words
A uniform mixture is called a solution. When a solid is mixed into a liquid, the solid is the solute and the liquid is the solvent. When two liquids are mixed, the one present in the smaller amount is the solute and the one in the larger amount is the solvent.
Worked example
Sugar syrup holds a great deal of sugar and rather little water. Which is the solute?
Check which rule applies: this is a solid mixed into a liquid, not two liquids mixed together.
The two rules give different answers here, so picking the right one is the whole question.
Try it together
Baking soda is stirred into 50 mL of water at 20 °C until some of it stops dissolving and sits at the bottom. The beaker is then heated to 50 °C.
A word or two for each answer.
1.At 20 °C the solid has stopped dissolving and is settling. What kind of solution is that, at that temperature?
Have a go
Have a go on your own. The amount of solute present in a fixed quantity of solution has a one-word name. What is it?
Ready to practice?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.