A mixture is two or more materials jumbled together — and what has been mixed can usually be un-mixed. At Mixing Marsh, Year 4 scientists learn which materials dissolve, and how to choose the right way to separate a mixture.
What your child will learn
- Know that a mixture can be separated because its parts are not joined
- Sort materials into soluble (dissolves) and insoluble (does not dissolve)
- Separate mixtures by sieving, filtering, using a magnet and evaporating
- Choose a method by thinking about how the parts are different
Use the difference
Every separating method relies on a difference. A sieve uses size: small grains fall through, big ones don’t. A magnet uses magnetism: it lifts out iron. A filter holds back solid bits while liquid passes through.
Dissolved, not gone
When salt dissolves in water it breaks into pieces too small to see, making a solution. It hasn’t disappeared — you can taste it. A filter can’t catch it, but if the water evaporates, the salt is left behind as crystals.
Example questions
Here are a few questions like the ones in the first quest. Can you solve them?
1. What could you use to pull iron nails out of sawdust?
🧲- A magnet
- A sieve
- A fan
- A spoon
Show answer
Answer: A magnet. Iron is attracted to a magnet; sawdust is not.
2. True or false? A fruit salad is a mixture.
Show answer
Answer: True. The pieces of fruit are mixed, and you could pick them apart again.
3. Muddy water is poured through paper in a funnel. What is this called?
- Freezing
- Melting
- Filtering
- Dissolving
Show answer
Answer: Filtering. The filter paper traps the mud and lets the water through.
Tips for grown-ups
- Mix sand, salt and paper clips, then work out together how to get each one back.
- Leave a saucer of salty water on a sunny windowsill and watch the crystals appear.
- Use a tea strainer or coffee filter and talk about what gets through.