Pick the Right Separation
Match each mixture to the best technique.
What this lesson covers
Why it matters
Iron filings hidden in sand, salt dissolved in water, camphor mixed with dirt — every messy mixture has a clever trick to pull it apart. Which tool for which job?
Predict first
You have salt water and you want to collect the PURE water back. Which method should you choose?
Distillation boils the water into steam, then cools the steam back into pure liquid water, leaving the salt behind in the flask.
- Filtration
- Distillation — correct
- Magnetic separation
- Sublimation
What you do
Drag each mixture to the separation technique that works best for it.
Check yourself
Why is distillation used to get pure water from salt water?
In distillation the mixture is boiled. Water turns to steam and travels away, then a cool surface condenses it back into pure liquid water. The salt cannot evaporate, so it is left behind.
Camphor mixed with sand can be separated by sublimation. What makes this work?
Sublimation separates a solid that turns directly into vapour on heating. Camphor (and ammonium chloride) sublime, so their vapour rises and can be re-solidified, while non-subliming sand or salt is left behind.
To separate iron filings from sand, which property of iron do we use?
Iron is attracted to a magnet, but sand is not. Moving a magnet over the mixture lifts out the iron filings and leaves the sand behind.
- The water boils into steam and is cooled back to pure liquid, leaving salt behind — correct
- The salt floats to the top and is scooped off
- The water passes through filter paper and the salt stays on top
- A magnet pulls the salt out of the water
- On heating, camphor changes straight from solid to vapour while sand stays behind — correct
- Camphor dissolves in the sand
- The sand melts and drains away
- A magnet attracts the camphor
- Iron is magnetic, so a magnet pulls it out of the mixture — correct
- Iron dissolves in water while sand does not
- Iron sublimes when heated
- Iron floats on water