Separating Mixtures Low Demand Questions

Transcription

1 Separating Mixtures Low Demand Questions 1. Pond dipping Abdi is collecting some living things from a pond. He pulls a net through the water. Describe how the net separates the water and pond life. (b) Abdi empties the net into a container of water. He decides to sort the animals he collected into groups. Abdi puts these two animals into the same group. Describe ONE feature that both these animals have. Abdi sorts four more of the pond animals into groups. Write A, B, C and D to show which group each animal belongs to in the diagram below. Some different animals have already been sorted.

2 2. Paper making 2 marks Some children want to recycle the scrap paper from their classroom. This is what the children do: Step 1: Cut the scrap paper into pieces Step 2: Put the pieces into a bowl. Step 3: Add water and leave overnight Step 4: Mash up the mixture. Now it is called pulp The children spread the pulp on to some wire mesh to dry. When the pulp is dry, it forms a sheet of recycled paper. The mesh has holes in it.

3 How do the holes in the mesh help the pulp to dry? (b) The children leave the pulp in their classroom. After two days, the pulp is completely dry. Name the process that causes the pulp to dry completely. What could the children do to make the pulp dry faster? 3. Mixing materials Seema and Alan are mixing materials. They put different materials in four clear plastic bags. They tie the top of each bag. They watch what happens and record their observations.

4 Mixture Bag A: Brown sugar and water. Observations Water turns brown and cannot see the sugar after a while. Bag B: Oil and water. Oil floats on top of the water. Bag C: Bicarbonate of soda and vinegar. Lots of fizzing. It looks frothy. Bag puffs up. Bag D: Bicarbonate of soda and oil. Bicarbonate goes in a lump at the bottom. Write the names of the THREE liquids that the children used. (i)... (ii)... (iii)... (b) Look at the table. In one bag dissolving was the only change. (d) In which bag was dissolving the only change? The mixture in Bag C fizzed and the bag puffed up. Why did Bag C puff up? Three of the mixtures can be separated to get the starting materials back again. One of the mixtures cannot be separated.

5 Which bag has a mixture that cannot be separated? Water and Salt Kiran puts 50cm 3 of water in a plastic beaker. He puts it in a freezer. He looks at the freezer thermometer. What is the temperature in the freezer?... C

6 (b) The water in the beaker turns to ice. Kiran takes the beaker out of the freezer. He puts it into a fridge. The diagrams below show what happened. beaker of water water turns to ice ice melts freezer fridge Why did the ice in the beaker melt in the cold fridge? Tick ONE box. the fridge was colder than the room there was less food in the fridge the fridge was bigger than the freezer the fridge was warmer than the freezer there was more air in the fridge Kiran puts 50cm 3 of water in another beaker. He adds 5g of salt. (d) What happens to the salt when Kiran mixes it with the water? Kiran leaves the beaker with water and salt in a warm place for a week. Complete the following sentences to describe what happens to the water and salt. (i) The water... (ii) The salt...

7 5. Powder The children grind up some green, sugar-coated chocolate sweets. They end up with a mixture of powder and some larger pieces. Which method should be used to separate the largest pieces of sweets from this mixture? Tick ONE box. sieving evaporating (b) filtering dissolving They add the mixture of powder and small pieces to water in a jar and stir. They leave the mixture to stand for two hours. Colour comes from the mixture. The liquid in the jar turns green. What process made the liquid turn green? After two hours there are still some small brown pieces left in the green liquid. Which method should be used to separate these brown pieces from the green liquid? Tick ONE box. condensing evaporating

8 filtering dissolving (d) The separated green liquid is heated gently on a radiator until only a green solid is left in the bottom of the dish. (e) 2 marks Explain what has happened to the water. How does the time taken for the mixture to dry depend on the temperature of the radiator?