Stir raisins into cereal and you have a mixture: each part keeps its own look and taste, and you can pick the raisins back out.
Key idea
A mixture is two or more things mixed together that keep their own properties. A solution is a mixture in which one thing dissolves evenly into another, like sugar in tea.
You can separate mixtures: pick out pieces by hand, pour through a sieve or filter, pull iron filings out with a magnet, or let the water evaporate to get dissolved salt back.
Why it works
The salt in salt water is not gone. It broke into pieces too small to see, spread through the water. Taste it, or let the water dry up, and the salt is there.
Worked example: Mass in a solution
You stir 20 g of salt into 200 g of water. What is the mass of the salt water?
- Dissolving does not destroy any matter.
- 20 g + 200 g = 220 g.
Answer: 220 g
Common mistake
Thinking dissolved salt has disappeared, so the salt water weighs the same as the water alone.
Try it at home
- Stir a spoonful of salt into a small glass of warm water until you cannot see it.
- Pour a little onto a dark plate and leave it in a sunny spot for a day or two.
- When the water has evaporated, the salt crystals are left behind.