Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
2. What were the patterns in the colours produced by:
a lithium salts burn with a crimson (carmine) red colour
b sodium salts burn with an orangy-yellow colour
c potassium salts potassium salts burn with a lilac colour
3. Which method do you think produced the best results Explain your answer.
Student choice.
4. Explain how you could use this technique to identify any metal ion components of an unknown salt –
for example, if a white powder was found at the scene of a crime, how could a flame test help to
identify the white powder
Since many metal ions burn with characteristic ‘fingerprint’ colours, the colour of the flame
of the unknown white powder could identify the metal ion in the white powder.
_Halogen reactions (pages 92–97)_________________
PRACTICAL Observing the reaction of halogens with iron
(pages 93–94)
Safety – take care with these practicals and ensure that you consult the relevant CLEAPSS
guidance.
1. Which halogen reacted most vigourously with the iron wool
Chlorine
2. Arrange the three halogens in order of reactivity, from most reactive to least reactive.
Chlorine then bromine then iodine
3. How does halogen reactivity vary as you go down Group 7
Halogen reactivity decreases down the Group.
4. Where would fluorine and astatine be on your halogen reactivity series
Fluorine would be above chlorine and astatine would be below iodine.
5. Write word and balanced symbol equations for the reactions of chlorine, bromine and iodine with
iron.
iron + chlorine → iron(III) chloride
2Fe(s) + 3Cl 2 (g) → 2FeCl 3 (s)
iron + bromine → iron(III) bromide
2Fe(s) + 3Br 2 (g) → 2FeBr 3 (s)
iron + iodine → iron(III) iodide
2Fe(s) + 3I 2 (g) → 2FeI 3 (s)
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