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Chemistry Unit 3.
1. How did John Newlands try to arrange elements in 1864?
By atomic mass. He had a `law of octaves', meaning every eighth element had similar properties (in
2. Why was Newlands' work not accepted?
The `law of octaves' only worked for the first 15 elements, after which there were many inconsistencies.
This is because many elements were not yet discovered.
3. How did Dmitri Mendeleev's work differ from Newlands'?
He arranged elements by atomic mass too, but left gaps when the pattern did not fit. He predicted the
properties of elements that were not yet discovered using this method.
4. What do elements in the same group have in common?
They have the same number of electrons in their outer shell.
5. What do elements in the same period have in common?
They have the same number of electron shells.
6. Why does reactivity increase as you go down group 1?
The number of electron shells increases as you progress down the group, meaning that the outer electron
is further away from the positive attraction of the nucleus. It is also more shielded from the attraction
when there are more electron shells between it and the nucleus. The outer electron is therefore more
7. What would you find in group 0 (or group 8), and why are these elements very unreactive?
The Noble gases. Their outer electron shells are full.
8. What gas would be given off when a group 1 metal reacted with water?
9. Name a special property of iodine
It sublimes. (Grey crystals/purple vapour)
10. What sort of molecules do halogens form?
Diatomic molecules. E.g. Cl2 ,F2,I2
11. Name four properties of transitions metals that make them useful.
a) They make good catalysts.
b) They form coloured compounds (can be used in paint etc.)
c) Good conductors of electricity
d) Do not react easily with water or oxygen.
12. What are the Lowry-Brønsted definitions of an acid and a base?
An acid is a `proton donator'. A base is a `proton acceptor'.
13. Why were the ideas of Lowry and Brønsted more readily accepted than those of Arrhenius?
They explained the behaviour of acids and bases in solvents other than water.
14. What makes strong acids and alkalis strong?
A strong acid or alkali is one that is completely ionised in water. Examples of strong acids are
hydrochloric, sulphuric and nitric acids. Examples of strong alkalis are sodium and potassium hydroxide.
15. What makes weak acids and alkalis weak?
A weak acid or alkali is only partially ionised in water. Examples of weak acids are ethanoic, citric and
carbonic acids. An example of a weak alkali is ammonia solution.
16. What sort of indicator would be used in a titration of each of the following:
-strong acid + strong alkali?
- strong acid + weak alkali?
- weak acid + strong alkali? phenolphthalein indicator.
strong acid + strong alkali any acid-base indicator; strong acid + weak alkali methyl orange indicator;
weak acid + strong alkali phenolphthalein indicator.
17. State two disadvantages to having hard water.
a) Lime scale build-up in kettles and central heating pipes.
b) Leaves soap scum/ soap does not lather easily
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State two ways to increase the solubility of a gas.
a) Decrease in temperature
b) Increase in pressure
19. How will global warming harm sea life?
Less oxygen will be able to dissolve in the water as the temperature increases, meaning sea life will not
be able to respire as much.
20. What makes hard water hard?
Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are
dissolved when water comes into contact with rocks.