The alkali metals lie on the far left of the periodic table, in the very first group
group 1 metal + water ⟶ metal hydroxide + hydrogen
2M (s) + 2H2O (l) ⟶ 2MOH (aq) + H2 (g)
where M is Li, Na, K, Rb or Cs
Remember the group 1 metals all produce alkaline solutions (>pH 7) when they react with water.Lithium will produce a solution of lithium hydroxide; sodium will produce a solution of sodium hydroxide and so on.Make sure you can give the reaction equations with the correct state symbols to show what is happening during the reactions!
Summary of the Reactions of the First Three Alkali Metals with Water
Summary of the Reactions of the First Three Alkali Metals with Oxygen
The melting point of the group 1 metals decreases as you descend the group
Trends are patterns of behaviour that change as you go down a group or across a period. Trends are not the same as rules, so sometimes there are odd properties that seem inconsistent, but the overall patterns remain the same.
You could be asked to make predictions about how rubidium would be expected to react with water, knowing that it lies below potassium in group 1. Words like 'explosively' and 'violently' would be good ones to choose when describing the reaction.