Sieving, filtering, magnets and more. Read, watch filtration, match the method, then play.
What it is
A mixture is two or more things mixed together. We separate them to remove something unwanted, or to keep the useful part.
Why it works
Sometimes the mixed-in thing is harmful or useless, like stones in rice, and sometimes the part we want is mixed in, like salt in sea water, so separating helps either way.
Why it matters
Separating mixtures is something we do in kitchens, farms and factories every day.
A few examples
We pick stones from rice to remove them. We dry sea water to keep the salt.
What it is
The best method depends on the mixture. Sieving sorts by size, filtration removes insoluble solids from a liquid, a magnet pulls out iron, winnowing uses wind, and evaporation gets dissolved solids back.
Why it works
Each method uses a difference between the things mixed, such as size, weight, magnetism or whether something dissolves, so we choose the one that fits.
Why it matters
Choosing the right method is the key skill in separation.
A few examples
Sand and pebbles: sieving. Muddy water: filtration. Iron and sand: a magnet.
What it is
We can look at a mixture and decide which method would separate it best, then group mixtures by method.
Why it works
Grouping mixtures by method builds the habit of spotting the useful difference, like magnetism or size, before we act.
Why it matters
This quick thinking is exactly how separation problems are solved.
A few examples
Muddy water is filtered. Iron and sand uses a magnet. Grain and husk is winnowed.
What it is
Handpicking removes a few visible impurities by hand, good for small amounts. Winnowing uses wind to blow away the lighter part, like husk from grain.
Why it works
These simple methods use what we can see or the difference in weight, needing no special tools, just hands or moving air.
Why it matters
Farmers and cooks have used these methods for centuries.
A few examples
We handpick stones from rice. We winnow grain to blow away the light husk.
What it is
In muddy water, heavy solids settle as sediment. Pouring off the clear water is decantation. Fine bits are then removed by filtration.
Why it works
Because heavier bits sink and finer bits are caught by filter paper, these steps together give clean water from a muddy mixture.
Why it matters
This is how dirty water is cleaned in many everyday situations.
A few examples
Mud settles as sediment. Clear water is decanted off. Filtration removes the rest.
What it is
When a solid is dissolved in water, filtering will not work. Instead we use evaporation: the water leaves as vapour and the solid is left behind.
Why it works
Since the dissolved solid spreads through the water, only removing the water by evaporation leaves it behind, which is how salt is recovered.
Why it matters
This is how sea salt is made and how we separate what has dissolved.
A few examples
Salt water dries in the Sun, the water evaporates, and the salt is left behind.
Muddy water is poured into the filter. Clean water drips through and the mud stays behind on the paper.
Drag each mixture to the best way to separate it. sorted 0/8
Have a go first, then tap to see the clear steps.
Q1. Why do we pick small stones out of rice?
Q2. Which method separates iron filings from sand?
Q3. How would you separate mud from muddy water?
Q4. What method uses wind to separate light husk from grain?
Q5. How do we get salt back from salt water?
Q6. Pouring off the clear water above settled mud is called what?