Science 3 · Unit 2: Mixing materials · Cambridge Primary Science Stage 3

Questions

1. 1. What does a filter do?

   • separates salt from water
   • makes solids dissolve
   • separates insoluble solids from a liquid
   • turns liquids into gases
   Check

2. 2. Why do solids stay in the filter?

   • They are lighter than water.
   • The pieces are too big to pass through the holes.
   • They are magnetic.
   • They dissolve.
   Check

3. 3. How is filter paper different from a sieve?

   • It has much smaller holes.
   • It has no holes.
   • It has much bigger holes.
   • It is magnetic.
   Check

4. 4. What is a funnel used for when filtering?

   • to hold the filter paper
   • to heat the mixture
   • to stir the mixture
   • to measure the water
   Check

5. 5. Why is filter paper good for filtering?

   • It is magnetic.
   • It has very tiny holes and stays strong when wet.
   • It dissolves in water.
   • It is waterproof.
   Check

6. 6. Can a filter separate sugar from water?

   • Only if you stir it.
   • Yes, the water stays in the filter.
   • No, because the sugar has dissolved.
   • Yes, the sugar stays in the filter.
   Check

7. 7. Can a filter separate salt from cooking oil?

   • No, filters only work with water.
   • No, because salt dissolves in oil.
   • Yes, because salt is insoluble in oil.
   • No, oil is a solid.
   Check

8. 8. What is the right order for filtering?

   • pour the mixture into the cup first
   • pour the mixture, then add the funnel
   • filter paper in the cup, then pour
   • cup under funnel, filter paper in funnel, pour the mixture
   Check

9. 9. Large filters clean waste water. What does the water drip through?

   • a magnet
   • layers of rock, gravel and sand
   • layers of salt and sugar
   • one sheet of plastic
   Check

10. 10. Why should you not drink water from your layered filter?

    • It is too cold.
    • It tastes of plastic.
    • It is a gas.
    • It could still have tiny dirt or germs in it.
    Check

11. 11. Arun and Sofia make a filter from a cup and a paper towel. What can it separate?

    • salt and water
    • sugar and water
    • vinegar and water
    • sand and water
    Check

12. 12. Sofia predicted the filtered water would be less dirty. It came out less dirty. Was she right?

    • Yes
    • No
    Check

13. 13. How could you make your layered filter better?

    • take away the sand
    • use bigger stones only
    • add more sand or a finer fabric
    • use no layers
    Check

14. 14. Dirty water is a mixture of ...

    • only solids
    • solid and liquid materials
    • only liquids
    • two gases
    Check