Edexcel IGCSE Chemistry Group 1 alkali metals
Practise Group 1 questions by describing water-reaction observations, choosing products and explaining reactivity from electron shells.
- Syllabus
- First assessment 2019
- Course
- Chemistry 4CH1
Practise Group 1 questions by describing water-reaction observations, choosing products and explaining reactivity from electron shells.
The diagram shows the positions of some elements in part of the Periodic Table.
Na Al S Cl
K Xe
In

A teacher adds a small piece of sodium to a glass trough containing water and universal indicator.
The universal indicator changes colour.
The equation for the reaction is
Explain the final colour of the universal indicator.
M1 (universal indicator turns) blue or purple
M2 because an alkali is produced
ACCEPT OH−/
hydroxide ions are
produced
ALLOW sodium
hydroxide is a base / a
base is produced
The teacher repeats the experiment with potassium instead of sodium.
Give one similarity and one difference observed with potassium.
similarity
difference
Similarity, any one from:
- both effervesce
- both melt / turn into a sphere
- both move on the surface
- universal indicator turns the same colour
Difference, any one from:
- potassium gives a lilac flame
- potassium moves faster
- potassium effervesces faster
Allow:
- fizzes / bubbles
- float
- both disappear / get smaller / dissolve
- faster / more vigorous reaction for potassium
- reverse arguments for sodium
Lithium, sodium and potassium are the first three elements in Group 1 of the Periodic Table.
Suggest why these three elements are all stored in paraffin oil.
to keep out of contact/prevent reaction with air/oxygen/water/moisture
ALLOW they react with air/oxygen/water/moisture
Caesium, Cs, is below potassium in Group 1.
Give a similarity and a difference between the reactions of potassium with water and caesium with water.
similarity
difference
similarity: both fizz/move on surface/ produce flame
ALLOW both melt/form a ball/produce a gas/ produce hydrogen/form an alkaline solution
difference caesium: faster/more violent reaction
ACCEPT reverse argument for potassium
ALLOW caesium explodes