Getting a Mixture Apart
- Chemistry
- Ages 8–11 · Grades 3–5
- Hands-on experiment
What you’ll find out
- In a mixture, each part keeps its own properties.
- Size, magnetism, dissolving and evaporating can each be used to separate parts.
- The order of the steps matters.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
Use what makes each part different
Imagine a bucket of gravel, sand, salt and iron filings, all mixed up. It is a mixture, so each part is still itself. The gravel is still gravel, and the salt is still salt. We can use what makes each part different to pull them apart. First, use size. Shake the mix through a sieve. The big gravel stays on top, and the smaller bits fall through. Next, use a magnet in a plastic bag. The iron filings jump up and stick to it. The sand and salt stay behind.
Dissolve, filter, dry
Sand and salt are harder to split. Their grains are about the same size, and neither is magnetic. But salt dissolves in water, and sand does not. So stir them into warm water. The salt dissolves and the sand sinks. Pour it all through filter paper in a funnel. The sand gets caught in the paper. The salty water goes through. Put the salty water in a dish on a warm windowsill. After a few days the water dries up. Salt crystals are left behind!
Curriculum links: NGSS 5-PS1-3