8ef test

Clevedon Community School

Science Department

Year 8 EF Test

Elements, Compounds and Reactions

26 min

43 marks

Answer all the questions

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1.

(a)

The table below shows the melting points of four metals.

(i)

metal

melting point, in °C

gold

1064

mercury

–37

sodium

98

iron

1540

Which metal in the table has the highest melting point? ............................................................

1 mark

(ii)

Which metal in the table has the lowest melting point? ............................................................

1 mark

(b)

Gold can be a gas or a liquid or a solid.

Choose from these words to fill the gaps below.

When gold is heated from room temperature to 1070°C, the gold changes from a ................................. to a ................................... .

1 mark

(c)

5 g of gold is melted and all of it is poured into a mould to make a pendant as shown below.

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What is the mass of the gold pendant? ........................... g 1 mark

(d)

The table below shows how the four metals react with oxygen when heated in air.

(i)

metal

reaction when heated in air

gold

no change

mercury

slowly forms a red powder

sodium

bursts into flames straight away

iron

very slowly turns black

Which is the most reactive metal in the table? ............................................................

1 mark

(ii)

Which is the least reactive metal in the table? ............................................................

1 mark Maximum 6 marks

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2.

The diagram shows a key which can be used to identify different chemicals.

Is the chemical green?

no

yes

When dilute hydrochloric acid is added, does the chemical fizz? no

Does the chemical dissolve in cold water? no

yes

calcium sulphate

(a)

sodium sulphate

When dilute hydrochloric acid is added, does the chemical fizz?

yes

no

Does the chemical dissolve in cold water? no

calcium carbonate

nickel sulphate

yes

nickel carbonate

yes

sodium carbonate

Use the key to identify chemicals A, B and C. (i)

Chemical A is a white powder. It fizzes when dilute hydrochloric acid is added. It dissolves in cold water.

Chemical A is .........................................................................................

1 mark

(ii)

Chemical B is a green powder. It does not fizz when dilute hydrochloric acid is added Chemical B is .........................................................................................

1 mark

(iii)

Chemical C is a white powder. It does not fizz when dilute hydrochloric acid is added. It is insoluble in cold water.

Chemical C is .........................................................................................

1 mark

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(b)

Nickel carbonate is green. It is the nickel that makes nickel carbonate green, not the carbonate. Explain, using information from the key, how you know that this is true. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................

2 marks Maximum 5 marks

3.

Some chemical reactions change raw materials into useful substances. (a)

Draw lines to connect each raw material to the substance produced from it. raw material

substance produced

clay

•

•

glass

ore

•

•

metal

sand

•

•

pottery

wood

•

•

paper 4 marks

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(b)

Listed below are five changes.

Tick the boxes by the two chemical changes. making yoghurt from milk

boiling water in an electric kettle

burning petrol in a car engine

diluting orange juice with water

making aluminium cans from a block of aluminium metal 2 marks Maximum 6 marks

4.

At school Ellen heated some copper powder until it went black. (a)

Give the name of the black substance formed when copper reacts with oxygen. .............................................

1 mark

(b)

Ellen added the black substance to some dilute sulphuric acid. The black substance reacted with sulphuric acid forming a blue solution of copper sulphate.

What type of substance is copper sulphate?

Tick the correct box. an acid

a compound

an element

a mixture 1 mark

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(c)

(i)

Ellen poured 20 cm3 of the blue copper sulphate solution into a dish, A, as shown below.

copper sulphate solution dish A She left the dish in a room at 21째C for two days.

What two changes would Ellen observe in dish A two days later?

1. .......................................................................................................

2. .......................................................................................................

2 marks

(ii)

Ellen poured 20 cm3 of the same blue copper sulphate solution into another dish, B. She put a lid on dish B and left it in the room at 21째C for two days.

lid

copper sulphate solution dish B After two days the contents of dish B looked different from the contents of dish A. Give one difference Ellen would observe and explain how the lid caused this difference. ............................................................................................................. ............................................................................................................. .............................................................................................................

2 marks Maximum 6 marks

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5.

Gold, iron and magnesium are elements which conduct electricity.

Sulphur and phosphorus are elements which do not conduct electricity.

When iron and sulphur are heated together, they react to form a new substance called iron sulphide.

(a)

From the substances named above, give: (i)

the name of a metal; .................................................................................................................

1 mark

(ii)

the name of an element which is a non-metal; .................................................................................................................

1 mark

(iii)

the name of an element which will rust; .................................................................................................................

1 mark

(iv)

the name of a compound. .................................................................................................................

1 mark

(b)

When magnesium and sulphur are heated together, they react.

Write the name of the compound which is formed when magnesium reacts with sulphur. ..........................................................................................................................

1 mark Maximum 5 marks

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6.

Two pupils heated some copper carbonate in a crucible. They recorded the mass of the crucible and contents before and after heating.

empty crucible

crucible and copper carbonate

crucible and copper oxide

mass = 50.00 g

mass = 51.24 g

mass = 50.80 g

The word equation for this reaction is: copper carbonate ď‚Ž copper oxide + carbon dioxide (i)

What mass of carbon dioxide is given off in this reaction?

Give the unit. .................................................................................................................

1 mark

(ii)

What is the name of this type of chemical reaction?

Tick the correct box. combustion oxidation reduction thermal decomposition 1 mark

(b)

The pupils then heated some magnesium in another crucible. They worked carefully and did not lose any of the magnesium oxide which formed.

They recorded the mass of the crucible and contents before and after heating.

(i)

empty crucible

crucible and magnesium

crucible and magnesium oxide

mass = 50.00 g

mass = 50.12 g

mass = 50.20 g

Write a word equation for the reaction. .................................................................................................................

1 mark

(ii)

Why does the mass of the contents of the crucible increase in this reaction?

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

1 mark

(iii)

What is this type of chemical reaction called? .................................................................................................................

1 mark Maximum 5 marks

7.

Copper can be obtained form its ore, copper sulphide, in two stages.

First stage

heating the ore in air Copper sulphide reacts with oxygen from the air to form copper oxide and sulphur dioxide gas.

Second stage

heating the copper oxide with carbon Copper oxide reacts with carbon to form copper and carbon dioxide gas.

(a)

Give the names of three elements mentioned above.

1. .................................................................................................................

2. .................................................................................................................

3. .................................................................................................................

1 mark

(b)

Give the name of one compound mentioned above. ..........................................................................................................................

1 mark

(c)

Give the name of the compound, mentioned above which causes ‘acid rain’. ..........................................................................................................................

1 mark Maximum 3 marks

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8.

The diagrams represent the arrangement of atoms or molecules in four different substances, A, B, C and D.

A

B

C

D not to scale

Each of the circles, (a)

(i)

,

and

represents an atom of a different element.

Which substance is a compound? …………

1 mark

(ii)

Which substance is a mixture? …………

1 mark

(iii)

Which two substances are elements? ………… and …………

1 mark

(iv)

Which two substances could be good thermal conductors? ………… and …………

1 mark

(v)

Which substance could be carbon dioxide? …………

1 mark

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(b)

The following experiment was set up. Test-tubes containing substances B and C were placed together as shown. The substances did not react.

They were left for five minutes.

test-tubes put together + mixture of substance B and substance C substance B (i)

substance C How many molecules are there in the mixture compared to the total number in substances B and C? ……………………………………….……………………………………….

1 mark

(ii)

Complete the diagram which is a model of this experiment.

+

substance B

substance C

mixture 1 mark Maximum 7 marks

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