Why Does Temperature Remain Constant When Water Boils?

[physgirl]

So if heat energy is transferred at a constant rate until the water reaches its boiling point temperature (in 6 min let's say)... and then heat energy is transferrred at the same rate as the water boils for the next 4 min...

would the graph of time v. temperature look like: a straight line with constant slope going from original water temperature to 100 degrees in the first 6 minutes and then a straight horizontal line b/w 6 min and 10 min?

also, if that is correct, for the last 4 minutes, is the temperature constant despite the heat energy transfer because... the energy was being spent on changing water to steam rather than increasing the temperature?

 

[rsk]

Yes and yes.