A student watches a demonstration of three alkali metals reacting with water.
The table shows the observations.
| Alkali metal | Observations |
|---|---|
| lithium | floats, fizzes steadily, does not melt |
| sodium | floats, fizzes rapidly, melts into a ball, moves quickly on the surface |
| potassium | floats, fizzes very rapidly, melts, burns with a lilac flame |
Put the three metals in order of reactivity, starting with the most reactive.
Rubidium is below potassium in group 1. Predict one observation when rubidium is added to water.
Explain why the alkali metals become more reactive down the group. Use ideas about electrons in your answer.
Write the balanced equation for the reaction of potassium with water. Include state symbols.
Explain why the solution formed turns universal indicator purple.
41 exam-style questions on Edexcel GCSE Chemistry 7.1 Group 1, covering 7.1.1 Classifying elements by group in the periodic table and 7.1.2 Properties and reactions of the alkali metals. Each one has a worked solution and a mark scheme showing where the marks go.