Describe the action of heat on their nitrates. use an equation to illustrate this

Thermal decomposition

Explanation:

The heating of nitrates to oxides to nitrate is known as thermal decomposition.

The nitrates are white solids, and the oxides produced are also white solids. Brown nitrogen dioxide gas is given off together with oxygen. Magnesium and calcium nitrates normally have water of crystallisation, and the solid may dissolve in its own water of crystallisation to make a colourless solution before it starts to decompose.

Again, if "X" represents any one of the elements:

2(NO3)2(g) _ 4NO2(g) + O2(g)

As you go down the Group, the nitrates also have to be heated more strongly before they will decompose.

the answer would be a