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7th grade chemical reactions, acids and bases

7th grade (Year 8 in England) · 16 questions · Common Core: NGSS.MS-PS1-2, NGSS.MS-PS1-5, NGSS.SEP 4 · England: KS3 Chemistry: Chemical reactions, KS3 Chemistry: Chemical reactions (acids and alkalis), GCSE Combined Science: Quantitative chemistry

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1
Question 1
A solution has a pH of 9. What colour will universal indicator turn?
- A. blue
- B. orange or yellow
- C. green
- D. red
Question 2
Complete the word equation: sodium + oxygen → ?
Answer
3
Question 3
Vinegar and baking soda react in an open beaker on a balance. The reading goes down. Is mass destroyed?
- A. No: carbon dioxide gas escapes into the air
- B. Yes: some atoms disappear
- C. Yes: chemical reactions always lose mass
- D. No: the balance is broken
4
Question 4
A solution has a pH of 7. Is it acidic, neutral or alkaline (basic)?
- A. acid
- B. neutral
- C. alkali (base)
5
Question 5
Why does a candle under a glass jar go out?
- A. The wax turns into water
- B. Glass puts out flames
- C. The jar gets too heavy
- D. The oxygen inside is used up
6
Question 6
Complete the word equation: calcium + oxygen → ___
- A. carbon dioxide
- B. calcium carbonate
- C. calcium oxide
- D. copper oxide
7
Question 7
Acids and alkalis: which statement is NOT true?
- A. All acids are dangerous.
- B. Alkalis are bases that dissolve in water.
- C. Strong acids and alkalis can be corrosive, so eye protection is needed.
- D. Pure water has a pH of 7.
8
Question 8
Universal indicator results: baking soda solution pH 9, vinegar pH 3, oven cleaner pH 13, milk pH 6. Which is the most alkaline?
- A. vinegar
- B. oven cleaner
- C. milk
- D. baking soda solution
9
Question 9
Why is limestone (calcium carbonate) heated in kilns?
- A. to make it heavier
- B. to make quicklime (calcium oxide) for cement and building
- C. to turn it into gold
- D. to make oxygen
Question 10
25 g of calcium carbonate is heated in an open tube until it all breaks down. 14 g of calcium oxide is left. What mass of carbon dioxide escaped, in g?
Answerg
11
Question 11
Which of these is an alkali (base)?
- A. hydrochloric acid
- B. vinegar
- C. orange juice
- D. sodium hydroxide solution
Question 12
In a sealed flask, 8 g of substance A reacts completely with 18 g of substance B. 4 g of product D forms along with product C. What mass of C forms, in g?
Answerg
13
Question 13
Combustion: which statement is NOT true?
- A. A fire can burn without oxygen.
- B. Combustion is a reaction with oxygen that releases energy.
- C. Burning fossil fuels releases carbon dioxide.
- D. Rusting is a slow oxidation reaction.
14
Question 14
Phenolphthalein is added to sodium hydroxide solution. What colour does it go?
- A. blue
- B. colourless
- C. yellow
- D. pink
Question 15
When 100 g of calcium carbonate is heated, it forms 56 g of calcium oxide and 44 g of carbon dioxide. What mass of carbon dioxide forms from 200 g of calcium carbonate, in g?
Answerg
16
Question 16
Why is a gas boiler with a poor air supply dangerous?
- A. Incomplete combustion produces toxic carbon monoxide
- B. It makes the water too pure
- C. It produces too much oxygen
- D. It stops producing heat completely

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Answer key: 7th grade chemical reactions, acids and bases

1. A. blue
2. sodium oxide
3. A. No: carbon dioxide gas escapes into the air
4. B. neutral
5. D. The oxygen inside is used up
6. C. calcium oxide
7. A. All acids are dangerous.
8. B. oven cleaner
9. B. to make quicklime (calcium oxide) for cement and building
10. 11 g
11. D. sodium hydroxide solution
12. 22 g
13. A. A fire can burn without oxygen.
14. D. pink
15. 88 g
16. A. Incomplete combustion produces toxic carbon monoxide