Key Stage 3 Science Book 2 Assessments
Explaining Chemical Changes (Orange level)
Answers
1. Which of the following conditions cannot be treated effectively by a neutralisation reaction? [1 mark]
d)
Difficulty level: moderate
Skill level: knowledge
2. Atoms of which two elements are always needed to make an alkali? [1 mark]
d)
Difficulty level: moderate
Skill level: knowledge
3. Zinc reacts with sulfuric acid to produce a gas that burns with a ‘pop’. Which of the following
statements is false? [1 mark]
c)
Difficulty level: moderate
Skill level: knowledge
4. There are several clues that a chemical reaction has happened. Which two of the following
observations are true for the reaction of an acid with a carbonate? [1 mark]
b), c)
Difficulty level: moderate
Skill level: knowledge
5. What will be formed if sulfuric acid neutralises magnesium hydroxide? [2 marks]
b), d)
Difficulty level: moderate
Skill level: application
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
6. Look at this picture of a metal reacting with an acid. What evidence is there that a reaction is taking
place?
(2 marks)
(the answer should include the following)
1) Bubbles of gas appearing
2) Over time, the amount of metal visible will decrease.
Difficulty level: moderate
Skill level: evaluation
7. Name the substances which are not gases that form when calcium carbonate reacts with hydrochloric
acid.
[2 marks]
(the answer should contain the following)
1) Calcium chloride
2) Water
Difficulty level: moderate
Skill level: knowledge
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
8. Calcium carbonate is added to hydrochloric acid in a flask on a balance. As time passes, the mass is
recorded and displayed on a graph. The graph is shown below. Explain what is happening and why. [4
marks]
(the answer should contain the following)
1) A reaction is taking place
2) Carbon dioxide is being released
3) As gas is released, so the mass descreases
4) Gradually, less gas is released and the mass settles down to a lower level
Difficulty level: hard
Skill level: evaluation
9. You are given two large bottles. Each contains a colourless liquid – one liquid is an acid, the other is an
alkali. Describe how you could decide which is which without affecting all of the liquid in each bottle. [2
marks]
(the answer should contain the following)
1) Take a small sample from each bottle
2) Add an indicator, such as litmus, to each of the samples and use the colour change to say which is
acid and which is alkaline
Difficulty level: moderate
Skill level: application
10. Which changes are characteristic of combustion reactions? [2 marks]
(the answer should contain the following)
1) A substance burns in air (reacts with oxygen in the air)
2) The reaction is exothermic (energy is transferred to the surroundings)
Difficulty level: moderate
Skill level: knowledge
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
11. Look at the diagram.
What colour would be produced if universal indicator solution is added to (a) lemon juice and (b)
ammonia?
[2 marks]
(the answer should contain the following)
1) (a) yellow-orange
2) (b) slightly purplish blue
Difficulty level: moderate
Skill level: application
12. Explain why combustion can lead to air pollution. [4 marks]
(the answer should contain the following)
1) Fossil fuels are burned in power stations and in various forms of transport, e.g. cars, lorries and
planes
2) Some fossil fuels contain sulfur impurities; when impure fossil fuels are burned, sulfur dioxide is
produced and becomes acid rain
3) Nitrogen oxides form when nitrogen in the air is oxidised during combustion
4) Sulfur dioxide and nitrogen oxides lead to acid rain
Difficulty level: moderate
Skill level: knowledge
13. Describe what happens when nitric acid is added to sodium hydroxide solution containing 2–3 drops
of litmus. Name the type of reaction that happened and the products of the reaction. [4 marks]
(the answer should contain the following)
1) The solution changes from blue to green (continuing to add nitric acid makes the solution red
eventually)
2) Neutralisation
3) Sodium nitrate
4) Water
Difficulty level: moderate
Skill level: application
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
14. Four indigestion tablets are tested by adding each to a beaker with acid in it.
Tablet brand
pH change
Time
(minutes)
A
1 to 3
20
B
1 to 5
3
C
1 to 5
4
D
1 to 4
4
Which is the most powerful antacid brand and why? [2 marks]
(answers should include the following)
1) B
2) It showed the biggest drop in pH in the shortest time
Difficulty level: hard
Skill level: application
© HarperCollinsPublishers 2014