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Reversible Changes

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Reversible Changes
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12/12/2011
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1. Changes



(a) Kim and Juan change the way some things look. The pictures below show the

changes.



Which changes are reversible? Tick ONE box for each change.



Is this change reversible?



Yes No



Bread Toast









Ice Water









Paper Ash









Plasticine Plasticine snail









2 marks

2. Drying sponge



(a) Dinesh puts a wet sponge on some scales.

He records its mass during the day.



He draws a graph of his results.



50



40





Mass of 30

sponge

(g) 20



10



0

0 1 2 3 4 5 6

Time (hours)



What is the mass of the wet sponge at the start of the investigation?



..................................................... g

1 mark







1

5(b) Describe how the mass of the wet sponge changes over the first four hours.



......................................................................................................................

1 mark



(c) What process causes the mass of the drying sponge to change?



......................................................................................................................

1 mark



(d) What is the mass of the dry sponge?



..................................................... g

1 mark



(e) Some other children discuss Dinesh’s results.

Look at their ideas below.



Use the graph to help you write true or false next to each idea.



The sponge dried

most quickly in the

first two hours. Bob









The sponge was

still drying after

Ruth five hours.









There was 20g of

Komal water in the

sponge at the start.







1 mark

3. Popcorn



(a) Sasha watches her father make some popcorn.



These pictures show what he does.



1. Put the corn in a saucepan. 2. Add some oil.









3. Put a lid on and heat the corn. 4. Add some salt.

sa

lt









2

Use the pictures.



Tick ONE box after each sentence to show if it is true or false.



The pictures show that as the corn pops, it...



True False





gets bigger.





changes to a darker colour.





changes shape.





gets smoother.

2 marks



(b) After the corn is cooked it is hot.



What should Sasha measure to find out how hot the popcorn is?

Tick ONE box.



Sasha should measure the...





mass. temperature.





volume. time to cook.

1 mark



(c) Look at the pictures above.



Tick ONE box to show what is most likely to cause the corn to change.



salt oil





heat saucepan

1 mark



(d) When corn is popped, a new material is formed.



This change is not reversible.



Describe a different non-reversible change where another new material is

formed.



.....................................................................................................................



.....................................................................................................................

1 mark



3

4. Heating and Cooling



(a) Some children want to see how food changes when it is heated and cooled.



They have five different kinds of food.







margarine



egg





chocolate





bread crisp



They use a small candle to heat each kind of food, then leave each to cool.









peg



candle







They use a peg to hold the food over the lighted candle.



Why is it safer to hold the food with a peg instead of with the hand?



......................................................................................................................



......................................................................................................................

1 mark



(b) To be safe, they put sand around the candle to hold it upright.



Give another reason why sand is a good material to have around a

lighted candle.



......................................................................................................................



......................................................................................................................

1 mark

(c) When margarine is heated, it melts and becomes a liquid.



When it cools, it goes back to a solid.



This is a reversible change.



Complete this table.



Write yes or no in each box.









4

Is the change

Food Change when heated

reversible?









2 marks



5. Water



(a) Scott has a plastic bottle with water in it.



He wants to freeze the water by putting the bottle in a freezer.



Complete the labels by writing solid or liquid in each box.



(i) The bottle before going into the freezer.





bottle









water









1 mark



(ii) The bottle just after being in the freezer for 24 hours.





bottle









ice









1 mark



6. Ice



(a) Some children pass round a block of ice.

Their hands feel cold and wet.







5

What is the name for the process when ice changes to water?



......................................................................................................................

1 mark



(b) What causes the ice to change to water as they pass the block round

from hand to hand?



......................................................................................................................

1 mark



(c) The children have four identical frozen ice sticks.

They put each one in a different place in the classroom.

They leave each of them for half an hour.









ice

stick









They cut open the plastic wrappers and pour out the liquid.



They measure the volume of liquid from each ice stick to find out how

much ice has turned to liquid.



Here are their results.



Volume of liquid after half an hour



Anna's Marcel's Gina's Daljit's

Place

desk desk desk desk





Volume of liquid

(cm3 ) 12 16 9 15









Use the table to answer the following questions.



At whose desk did most of the ice stick stay frozen?



......................................................................................................................

1 mark



(d) (i) Which of the four desks was in the warmest part of the classroom?



............................................................................................................

1 mark



(ii) Explain how you know which place was warmest.



............................................................................................................



............................................................................................................

1 mark





6

7. Acid rain



(a) Sometimes rain mixes with pollution in the air to form acid rain.



Some children want to find out what happens when acid rain falls on rocks.



Vinegar can be used to show the effects of acid rain. The children

add vinegar to chalk rock. The pictures below show what happens.



bubble







vinegar



dish



Chalk rock Chalk rock and

vinegar





Bubbles are produced.



Write true or false next to each sentence below.



The change is non-reversible. ...............................................



The bubbles evaporate. ...............................................

1 mark



(b) Write solid, liquid or gas next to each material in the table.



Material Solid, liquid or gas?



inside the

bubble



vinegar



chalk rock

1 mark



(c) The children test more rocks. The table below shows their results.



Are bubbles produced

Rock

when vinegar is added?



granite no



sandstone no



limestone yes



slate no



pumice yes









7

Look at these pictures of a statue. The statue is in a city that has acid rain.









Statue when new Same statue after 200 years



Use the table to name ONE rock that this statue could have been made from.



...............................................

1 mark

8. Puddle



(a) It rained in the night. There was a puddle in the playground.



During the morning the puddle became smaller.



Children measured the width of the puddle at different times.

Plan of puddle









11:30 a.m.





10:30 a.m.





10:00 a.m.





Draw a ring on the plan to show the size of the puddle at 11 o’clock.

1 mark







(b) The puddle got smaller. No water soaked into the playground.



Explain what happened to the water.



......................................................................................................................

1 mark



(c) The graph shows how a puddle 150 cm wide changed on a cold day.



Draw a different line to show how a puddle 150 cm wide changed on a

warmer day. 150



125

2 marks

100



width of 75

(d) Explain why the two lines are different. puddle

in cm

50

............................................................................

25 B

................................................................1 mark

0

7.00 8.00 9.00 10.00 11.00 12.00

time of day

8

(e) What happened at B?



......................................................................................................................

1 mark



9. 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.



Mixture Observations

Bag A: Brown sugar Water turns brown and cannot

and water. see the sugar after a while.









Bag B: Oil and water. Oil floats on top of the water.









Bag C: Bicarbonate of Lots of fizzing. It looks frothy.

soda and vinegar. Bag puffs up.









Bag D: Bicarbonate of Bicarbonate goes in a lump

soda and oil. at the bottom.









(a) Write the names of the THREE liquids that the children used.



(i) ...............................................



(ii) ...............................................



(iii) ...............................................

1 mark



(b) Look at the table. In one bag dissolving was the only change.



In which bag was dissolving the only change?



......................................................................................................................

1 mark



(c) The mixture in Bag C fizzed and the bag puffed up.



Why did Bag C puff up?



..........................................................................................................1 mark



9

(d) Three of the mixtures can be separated to get the starting materials back

again. One of the mixtures cannot be separated.



Which bag has a mixture that cannot be separated?



..........................................................

1 mark



10. Adding water



(a) Safara wants to find out what happens when solids are mixed with water.



She adds water to four different solids and stirs the mixtures. After 20 minutes

she draws pictures of her results.





colourless cloudy

liquid liquid



solid brown

pieces solid

beaker A beaker B





colourless coloured

liquid liquid

bubble



beaker C beaker D



The table below names the four solids that Safara mixed with water.



Which solid was in each beaker?



Write A, B, C or D to complete each row of the table.



Solid Beaker



soil



vitamin tablet



plastic beads



salt

1 mark



(b) Explain what happened to the solid in beaker C.



.....................................................................................................................

1 mark



(c) In which beaker was there a non-reversible change?



Beaker ............................................

1 mark



(d) Safara wants to separate the soil from her mixture of soil and water.







10

Tick ONE box to show which equipment would be best for separating the soil

from the water.





35



30



25



20



15



10



5



0









1 mark



(e) Safara wants to separate the salt from her mixture of salt and water.



Describe how Safara could get solid salt back from the salt and water mixture.



.....................................................................................................................



.....................................................................................................................

1 mark



11. Temperature



(a) John has four jars with water in them.









He measures the temperature of the water in each jar using a thermometer.

These are the four readings he takes in °C.



0° 15° 40° 60°



Fill in the table by putting these temperatures in the correct places.





Jar with: Temperature of water, C



cool water



water and ice



hot water



warm water

1 mark





11

(b) The temperature of the classroom is always 18°C.



What will happen to the ice floating in the water?



......................................................................................................................



......................................................................................................................

1 mark







(c) John puts out two new jars of water.



He writes the temperatures on the jars.



Next morning, the temperatures of the water in the jars have changed.



The room temperature is still 18°C.



Write in the boxes the temperatures of the water the next morning.









12 ºC 48 ºC





ºC ºC

1 mark



12. Sun and Light









Clothes were drying on a washing line.



The water in the clothes turns into water vapour in the air.



(a) Write the name of the change from water to water vapour.



......................................................................................................................

1 mark







(b) Rain forms from water vapour in the air.



Write the name of the change from water vapour to liquid.



......................................................................................................................

1 mark







12

13. Mixing Liquids



(a) Some children add vinegar to warm milk. They stir the mixture before it cools

down. The mixture changes very quickly.









Before mixing: After mixing:

milk and vinegar liquid and a white solid



This change is not reversible.



Can the children get the milk and vinegar back?



Tick ONE box in each row.



Yes No





(i) Can they get the milk back?





(ii) Can they get the vinegar back?

1 mark



(b) Which of the following suggests that this change is NOT reversible?



Tick ONE box.



In their test...



they stirred the mixture. there was liquid left.





a solid formed. the change was quick.

1 mark

(c) Nizam thinks that the more vinegar they use in the mixture, the bigger the white

ball will be.



Complete the sentence below to show how the children could test Nizam’s idea.



Put the same amount of milk in three identical containers and then



......................................................................................................................



......................................................................................................................

1 mark



(d) The children test Nizam’s idea. They try measuring around the white balls. But the

balls squash easily and the measurements change.



13

Before After









What better method could they use to find out if some of the white balls are bigger

than others?



......................................................................................................................



......................................................................................................................

1 mark



14. Washing day



(a) Some children have washed a jumper.







Why does the jumper feel heavier after it is washed?



......................................................................................................................

1 mark

(b) The children want to find out how long the jumper takes to dry.



They hang the jumper up to dry.







Name the process that completely dries the jumper.



......................................................................................................................

1 mark



(c) The children weigh the jumper every hour.



They make a graph of their results.









How many hours did the jumper take to dry?



.....................................................…hours

1 mark





14

(d) The children repeat their test the next day. They wash and dry the same jumper in

the same way. The jumper dries more quickly.



Give ONE possible reason why the jumper dries more quickly when they repeat

their test.



......................................................................................................................

1 mark



15. Dissolving



Sue has three different types of sugar.

She has:



large grain sugar



medium grain sugar

Sugar A: large grains

small grain sugar.









Sugar B: medium grains Sugar C: small grains



Sue measures how long it takes for 10g of each type of sugar to dissolve in 50cm3 of

water.



She keeps the amount of stirring the same each time.



Sue does her test three times. Here are her results.



Type of sugar Time taken for sugar to dissolve at

room temperature (seconds)



Sugar A: large grains 360 365 370



Sugar B: medium grains 190 215 200



Sugar C: small grains 160 165 161



(a) Look at the table.



Which type of sugar dissolved fastest?



......................................................................................................................

1 mark



(b) Sue's test was fair. She did her test more than once.



Explain why Sue did the test more than once.



......................................................................................................................

1 mark





15

(c) Use the table to say how the size of the sugar grains affects the time it takes for

the sugar to dissolve.



......................................................................................................................



......................................................................................................................

2 marks

16. Burning Candles



(a) Dianne put a wax candle on some scales.



The teacher lit the candle and left it to burn.







Dianne noticed a liquid around the bottom of the wick.









What is this liquid?



......................................................................................................................

1 mark



(b) Write the name of the process when a solid turns to a liquid.



......................................................................................................................

1 mark



(c) Dianne measured the mass of the candle every 30 minutes.



Her results are shown on this graph.









Look at the graph.



What happened to the mass of the candle while it was burning?



......................................................................................................................

1 mark







16

(d) Gareth said, ‘When the candle wax burns, the change can be reversed.’



Dianne did not agree with him. She said, ‘This change is irreversible’.



Explain why Dianne is correct.



......................................................................................................................



......................................................................................................................

1 mark

17. The water cycle



(a) This picture shows part of the water cycle.









stream



river



sea







Tick ONE box to say what the arrow shows.



cold water rising water vapour condensing





water evaporating gas changing to liquid

1 mark



(b) Tick ONE box in each row to show if each sentence is true or false.



Clouds form ...



True False



from water produced by condensation.





from water vapour in the air.

1 mark



(c) In the water cycle, water from the sea becomes rain water.



Why is rain water not salty when it comes from salty sea water?



......................................................................................................................



......................................................................................................................

1 mark









17


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