When a freshly cut piece of potassium is exposed to air, its appearance changes rapidly. Which statement describes this change?

• A It turns from a dull grey to a shiny silver.
• B It bursts immediately into a lilac flame.
• C It tarnishes quickly from shiny silver to dull grey.
• D It remains shiny and unchanged.

When potassium is added to cold water in a trough, hydrogen gas is formed. Describe the test used to confirm the presence of hydrogen gas, including the positive result.

A few drops of phenolphthalein indicator are added to the solution after the potassium has completely reacted. Describe and explain the colour change observed.

The table below shows some information about lithium oxide and lithium carbonate.

Identify the missing chemical formulae for (i) and (ii).

Lithium is another element in Group 1 of the Periodic Table. Identify the two correct statements from the list below comparing the reaction of lithium with cold water to the reaction of sodium with cold water:

1. The reaction with lithium is less vigorous than with sodium.
2. The reaction with lithium produces oxygen gas instead of hydrogen.
3. The reaction with lithium has a faster rate of bubble formation than with sodium.
4. The reaction with lithium produces a different hydroxide compound than sodium.
5. The reaction with lithium is endothermic.

Write a balanced chemical equation for the reaction of lithium with water.