GCSE

1 (a) In this apparatus hydrochloric acid is decomposed by passing a direct electric current through it. Chlorine and hydrogen are formed. (i) Give the name of this process in which substances, such as hydrochloric acid, are decomposed by a direct electric current.
(1)
electrolysis (ii) Describe what happens when a burning splint is applied to a mixture of hydrogen and air in a test tube.
(2)

(b) (i) Complete the sentence by putting a cross ( ) in the box next to your answer. An acid is present in the stomach of humans. This acid is
(1)
B hydrochloric acid

(ii) Some people suffer from indigestion and take indigestion remedies. Which of these could cure indigestion caused by excess acid? Put a cross in the box next to your answer.
(1)
A sodium chloride B carbon dioxide C calcium carbonate D hydrogen chloride (iii) Explain how an indigestion remedy works when it cures acid indigestion.
(2)
....................................................................................................................................................................................................................................................................................6
*P41936A0620*
The Earth’s atmosphere
2 (a) This apparatus was used to find the percentage of oxygen in a sample of air. Dry air was passed backwards and forwards over the hot copper. The copper turned black. The apparatus was allowed to cool. The volume of gas in the apparatus had decreased. (i) Explain why the volume of gas had decreased.
(2)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
(ii) Complete the sentence by putting a cross ( ) in the box next to your answer. The percentage of oxygen in dry air is
(1)
A 0.1 B 1.0 C 21 D 79 (b) The composition of the Earth’s earliest atmosphere was different to that of the present atmosphere. (i) Which of these gases was present in large amounts in the Earth’s earliest atmosphere? Put a cross in the box next to your answer.
(1)
A oxygen B carbon dioxide C ammonia D nitrogen (ii) The Earth’s early atmosphere contained a larger percentage of water vapour than the Earth’s atmosphere today. Explain what happened to cause the percentage of water vapour in the Earth’s atmosphere to decrease.
(3)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................

Metals
3 (a) Use words from the box to complete the sentences.
Electricity copper carbon methane water
(2)
(i) Iron is extracted from its ore by heating the ore with........................................................................................ (ii) It is difficult to reduce aluminium ore to aluminium metal. Therefore, to produce aluminium from its ore, it is necessary to use........................................................................................ (b) Lead oxide can be converted into lead by heating it with carbon. The word equation for the reaction is
Lead oxide + carbon lead + carbon dioxide Explain how this equation shows that lead oxide is reduced and carbon is oxidised.
(2)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
(c) The table shows some information about the metals copper and aluminium Use the information from the table to explain why aluminium, rather than copper, is used for overhead power cables.
(2)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................