Key Stage 3 Science Book 2 Assessments
Explaining Chemical Changes (Purple level)
Answers
1. Which of the following conditions cannot be treated by a neutralisation reaction? [1 mark]
d)
Difficulty level: moderate
Skill level: knowledge
2. Which of the following statements is false? [1 mark]
b)
Difficulty level: difficult
Skill level: knowledge
3. Atoms of which two elements are always needed to make an alkali? [1 mark]
d)
Difficulty level: moderate
Skill level: knowledge
4. Which of the following will neutralise stomach acid most quickly? [1 mark]
c)
Difficulty level: difficult
Skill level: application
5. 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
6. When Battersea Power Station was built in the 1930s, it had scrubbers to remove sulfur dioxide.
Water was used to dissolve the gas and, in the presence of an iron oxide catalyst, it was converted into
sulfuric acid. However, the scrubbing process was discontinued in 1960. Which of the following was the
reason the process was stopped?
[1 mark]
c)
Difficulty level: difficult
Skill level: knowledge
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
7. Which two of the following explain why alkali is usually found in toothpaste? [1 mark]
a), d)
Difficulty level: moderate
Skill level: application
8. Which two of the following describe what happens when magnesium burns in air? [1 mark]
a), c)
Difficulty level: knowledge
Skill level: knowledge
9. 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
10. Explain the difference between a base and an alkali. [2 marks]
(the answer should contain the following)
1) A base neutralises acids (to form a salt and water); it may be soluble or insoluble in water
2) An alkali is a base that dissolves in water
Difficulty level: difficult
Skill level: knowledge
11. 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
© HarperCollinsPublishers 2014
Key Stage 3 Science Book 2 Assessments
12. 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: difficult
Skill level: application
13. Explain why the idea that all chemical reactions heat up the surroundings is a misconception. [2
marks]
(the answer should contain the following)
1) Many reactions transfer energy to the surroundings, heating them; these are exothermic reactions
2) However, sometimes energy is transferred from the surroundings to the reacting substances and the
temperature of the surroundings decreases; these are endothermic reactions
Difficulty level: difficult
Skill level: knowledge
14. 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
15. Look at the picture of the apparatus. It shows a burning candle floating on water inside a bell jar.
Explain how this apparatus could be used to give a rough idea of how much oxygen is in air. [4 marks]
(the answer should contain the following)
1) The candle burns until all of the oxygen in the air has been used up
2) The volume of air in the container could be estimated
3) The volume of gas in the container after the candle was gone out could be estimated
4) The difference between the two volumes is an approximate measure of the amount of oxygen in air
and, from the two measurements, the percentage by volume of oxygen in air can be calculated
Difficulty level: difficult
Skill level: application
16. James sets up an experiment using a glass tank and three candles. He makes some carbon dioxide
and points it into the other end of the tank. First the shortest candle goes out, then the middle one and
then the tallest one. What conclusions can he draw? [4 marks]
(answers should contain the following)
1) Carbon dioxide is heavier than air
2) Carbon dioxide extinguishes flames
3) The short candle goes out first because the gas covers it first
4) The tallest candles goes out last because it takes longer for the gas to fill up to that level
Difficulty level: difficult
Skill level: evaluation
© HarperCollinsPublishers 2014