What must be true for any endothermic reaction?

The chemical bonds of the products have more energy than the chemical bonds of the reactants.

There are more products than there are reactants.

There must be a phase change from solid to liquid or from liquid to gas. (I think it's this one)

The reaction must take place in a sealed container held at constant volume.

Question

What must be true for any endothermic reaction?

 The chemical bonds of the products have more energy than the chemical bonds of the reactants.

 There are more products than there are reactants.

 There must be a phase change from solid to liquid or from liquid to gas. (I think it's this one)

 The reaction must take place in a sealed container held at constant volume.

thomaster · Answer

Endothermic reactions need energy. Exothermic reactions releases energy.
Therefore, the bonds of endothermic reaction products have more energy than the bonds of the reactants of endothermic reactions.