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Science questions, unit 7
Nama / NameKelas / ClassTarikh / Date

Density

28 marks. Use Practice to check each answer as you go, or Exam to answer everything first and then check.

Section A: objective questions

8 marks
Choose the best answer for each question.
1

Question 1

Which object floats on water?
Show answerHide answer
C
A cork floats. A coin, a marble and a stone sink (textbook pp. 96–97).
For the teacher: Remembering, low difficulty, standard 7.1.1
Textbook p. 97
2

Question 2

An object that is more dense than water will ______.
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A
Objects that are more dense than water sink. Objects that are less dense than water float.
For the teacher: Remembering, low difficulty, standard 7.1.2
Textbook p. 98
3

Question 3

Diagram 1 shows a sponge and a bar of soap in a tank of water. Why does the sponge float?
The sponge floats at the top of the tank and the soap lies at the bottom
Diagram 1
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C
The sponge has a lot of air space, so it is less dense than water and floats. The soap has no air space, so it sinks.
For the teacher: Understanding, low difficulty, standard 7.1.2
Textbook p. 98
4

Question 4

Diagram 2 shows a grape at the bottom of a beaker of water. What can Mei Ling stir into the water to make the grape float?
A grape at the bottom of a beaker of water
Diagram 2
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B
Salt dissolves and makes the water more dense, so the grape floats. Sand and stones do not dissolve. Plain water does not change the density.
For the teacher: Applying, medium difficulty, standard 7.1.3
Textbook p. 100
5

Question 5

Which thing uses density to keep us safe in water?
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A
A life jacket is less dense than water, so it floats and keeps us on the surface.
For the teacher: Remembering, low difficulty, standard 7.1.4
Textbook p. 102
6

Question 6

Diagram 3 shows three liquids, J, K and L, in a container. They do not mix. Which liquid is the most dense?
Three liquid layers: J on top, K in the middle, L at the bottom
Diagram 3
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D
The most dense liquid goes to the bottom. L is at the bottom, so L is the most dense. J, at the top, is the least dense.
For the teacher: Understanding, medium difficulty, standard 7.1.3
Textbook p. 101
7

Question 7

Big logs float on the river. Why?
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B
Objects that are less dense than water float. Being long or heavy does not decide it.
For the teacher: Understanding, low difficulty, standard 7.1.2
Textbook p. 99
8

Question 8

A ship and its anchor are both made of iron. The ship floats but the anchor sinks. Why does the ship float?
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D
The ship is hollow and full of air, so the whole ship is less dense than water. The anchor is solid iron, so it is more dense than water and sinks.
For the teacher: Understanding, medium difficulty, standard 7.1.4
Textbook p. 102

Section B: structured questions

20 marks
Answer all questions. Write your answers in the spaces provided.
9

Question 9

Diagram 4 shows four objects, P, Q, R and S. They are put into a basin of water. Does each object float or sink?
P is a paper clip, Q is an apple, R is a feather (quill), S is a grape
Diagram 4
[1 mark] (a)P (paper clip)
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Sink
[1 mark] (b)Q (apple)
Show answerHide answer
Float
[1 mark] (c)R (feather)
Show answerHide answer
Float
[1 mark] (d)S (grape)
Show answerHide answer
Sink
Textbook answer (p. 104): the apple and the quill float; the paper clip and the grape sink.
For the teacher: Applying, low difficulty, standard 7.1.1
Textbook p. 104
10

Question 10

Diagram 5 shows cooking oil and water in a glass. Choose the correct word.
A glass with cooking oil on top of water
Diagram 5
[1 mark] (a)Cooking oil will ______ on the surface of the water.
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float
[1 mark] (b)This is because cooking oil is ______ dense than water.
Show answerHide answer
less
[1 mark] (c)An object that is ______ dense than water will sink.
Show answerHide answer
more
For the teacher: Remembering, low difficulty, standard 7.1.2
Textbook p. 104
11

Question 11

Diagram 6 shows four objects, P, Q, R and S, in a tank of water.
P and R are on the water surface. Q and S are at the bottom of the tank.
Diagram 6
[1 mark] (a)Which objects are less dense than water?
Show answerHide answer
P and R float, so they are less dense than water.
Tick each point you got.
[1 mark] (b)Q is a bar of soap. Explain why it sinks.
Show answerHide answer
Tick each point you got.
For the teacher: Analysing, medium difficulty, standard 7.1.2
Textbook p. 98
12

Question 12

Aina put a carrot fish in 200 mℓ of water. She added sugar one spoonful at a time and stirred. Diagram 7 shows the fish before and after. The table shows her results.
Spoonfuls of sugar01234
Carrot fishSinksSinksSinksFloatsFloats
The carrot fish at the bottom of the beaker
Before
The carrot fish floating in the beaker
After
[1 mark] (a)How many spoonfuls of sugar did Aina need to make the fish float?
Show answerHide answer
Tick each point you got.
[1 mark] (b)What happens to the water when sugar dissolves in it?
Show answerHide answer
It becomes more dense
For the teacher: Analysing, medium difficulty, standard 7.1.3
Textbook p. 100
13

Question 13

Are these sentences true or false?
[1 mark] (a)A big, heavy log always sinks in water.
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False
Logs float because they are less dense than water (textbook p. 99).
[1 mark] (b)The most dense liquid stays at the bottom of the container.
Show answerHide answer
True
For the teacher: Understanding, low difficulty, standard 7.1.2
Textbook p. 99
14

Question 14

Diagram 8 shows two ways density helps us.
A boy swimming in a life jacket
Life jacket
Fish farm cages held up by blue drums
Fish farm
[1 mark] (a)How does a life jacket save a life?
Show answerHide answer
Textbook answer (p. 104).
Tick each point you got.
[1 mark] (b)The blue drums hold up the fish cages. The drums are ______ than water.
Show answerHide answer
less dense
For the teacher: Applying, low difficulty, standard 7.1.4
Textbook p. 102
15

Question 15

Diagram 9 shows an orange floating in a beaker of water. Siti says, "If I stir a lot of salt into the water, the orange will sink."
An orange floating in a beaker of water
Diagram 9
[2 marks] (a)Do you agree with Siti? Give a reason.
Show answerHide answer
Tick each point you got.
[1 mark] (b)Suggest one way to make the orange sink.
Show answerHide answer
Textbook HOTS answer (p. 104). The skin has many air spaces.
Tick each point you got.
For the teacher: Evaluating, high difficulty, standard 7.1.3
Textbook p. 104
16

Question 16

Ahmad wants to make a small raft to carry his toy across the drain in front of his house. He has these things:
ice cream sticks, coins, empty plastic bottles with caps, marbles, stones
A boy beside a drain with ice cream sticks, plastic bottles, coins, marbles and stones
Diagram 8
[1 mark] (a)Choose two things Ahmad should use to build his raft.
Show answerHide answer
Tick each point you got.
[1 mark] (b)Explain your choice.
Show answerHide answer
Tick each point you got.
For the teacher: Creating, high difficulty, standard 7.1.4
Textbook p. 102