Is heat being added or taken away when water boils?
Heat is being added in a way that does not result in a temperature change in the water, but that heat energy is used to increase the Potential energy of water by increasing the amount of space between each of the water molecules.
Well, when the water boils it undergoes a phase change...
Now clearly, energy has to be added to water to get it to the boiling point. But once at the boiling point, MORE energy has to be expended to effect the phase change between water as a liquid, and water as a gas, i.e. steam.