(a)[4]
State which one of these substances, R, S, T or U, (i) is an element (ii) has ionic bonds (iii) is a gas at room temperature (iv) is a polymer.
(b)[2]
Ammonium chloride appears in some fertilisers. Which two of the following compounds are also found in many fertilisers? Tick two boxes.
(c)[2]
The filter paper turns from red to yellow. Explain why this happens.