End of Unit Test
8G
Name
Class
Date
1 For each substance in the table below, below, identify whether they are elements, mixtures or compounds. Write your answer in the table. Subs Su bsta tanc nce e
Elem El emen ent, t, mi mixt xtur ure e or co comp mpou ound nd
a air b copper
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c oxygen d water
[3 marks]
2 Look at the diagrams below. below. Match the correct diagram to the description. Write the letter of the diagram in the table.
A
B
C
Description
D
Letter
a molecules of an element b molecules of a compound c a mixture of different elements d a mixture of elements and a compound
[4 marks]
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edition
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8G
End of Unit Test (continued)
3 Sonia and Aaron were given some solid silver carbonate to carry out some experiments. Silver carbonate (Ag2CO3) is a compound containing the elements silver, carbon and oxygen. First they heated the silver carbonate in a test tube. Small beads of silver metal formed and two gases were given off: carbon dioxide and oxygen. Then they collected the silver and mixed it with some tin. They heated the metals until they melted, so they could mix them together. a Use the above information to write a word equation for the chemical reaction which happened when the silver carbonate was heated. ___________________________________________________________________________________ [2 marks]
b How would Sonia and Aaron be able to tell that a chemical reaction was taking place as they were heating the silver carbonate?
___________________________________________________________________________________ [1 mark]
c From the substances in the passage, name one pure compound.
___________________________________________________________________________________ [1 mark] 1600
4 Some jewellers make things out of brass, which is a mixture of copper and zinc.
1500 1400
The graph shows how the melting point of the mixture changes as you add more zinc.
1300 1200 1100
a What is a mixture of metals called?
____________________________________ b How does adding more zinc to the mixture affect the melting point?
) C 1000 ° ( t n 900 i o p 800 g n 700 i t l e 600 M
500 400 300
200
____________________________________
100
[2 marks]
0 0
10
20
30
40
50
60
70
80
90 100
Content of zinc (%)
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8 G
8G
End of Unit Test (continued)
5 The graph shows what happens to the temperature of a solid when it was heated until it melted. 90
a What happened to the temperature in the first 4 minutes?
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_________________________
_________________________
80 70 ) C º ( 60 e r 50 u t a r 40 e p m e30 T 20 10
[1 mark]
0 0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20
Time minutes
b What happened to the temperature between 4 and 10 minutes?
___________________________________________________________________________________ [1 mark]
c What is the temperature after 2 minutes?
____________________________________ [1 mark]
d When did the liquid start to melt?
___________________________________________________________________________________ [1 mark]
e What is the melting point of the solid? Give the unit.
__________________________________ [1 mark]
f How can you tell from these results that the solid is probably pure?
___________________________________________________________________________________ [1 mark]
g The heat was turned off after 11 minutes and the tube was left to cool. On the grid above, draw the shape of the graph that you would get. Continue the line as far as 20 minutes. [2 marks]
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8G
End of Unit Test (continued)
6 Some of the materials used in jewellery making are shown in the table below. Material
Symbol/formula Properties
gold
Au
yellow solid, malleable, shiny when polished, very unreactive
diamonds
C
colourless solid, see through, very hard, unreactive
rhinestone
SiO2
colourless solid, see through, hard, unreactive
silver
Ag
silver solid, malleable, shiny when polished, unreactive
malachite
CuCO3
green solid, breaks easily, reacts when heated
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a Which materials in the table are elements?
___________________________________________________________________________________ [1 mark]
b Gold and silver are ‘malleable’. What does this mean?
___________________________________________________________________________________ [1 mark]
c How many elements are in rhinestones?
____________________________________ [1 mark]
d When malachite is heated, copper oxide and carbon dioxide are formed. The chemical name for malachite is copper carbonate. When this mineral is heated two substances are formed - coper oxide and carbon dioxide. Write a word equation for the reaction that happens when malachite is heated.
[1 mark]
____________________________________
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edition
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