Kettles boiling

Last week we bought a new kettle, we had to because I ruined the last one by putting it on the heat to make a cup of tea then forgetting about it. The new one has a much better whistle so hopefully I won't do the same thing again.The whistle takes some time to build up but once its going its quite loud. When taken off the heat it goes quite in a matter of seconds. Must be an EE in there somewhere. A couple of weeks ago, I was doing about the different power stations with my SL class. We almost finished the whole of the SL core this year. One of the students asked why steam is used to blow the turbine and not a gas. It seems such a waste to boil all that water just so we have to turn it back to liquid again in the condenser. It's not easy to explain especially since there isn't any fluid mechanics on the syllabus. If you think about a pressure cooker. What happens to all the heat energy when the water is boiled at 100°C with the lid on. It's not KE of the molecules because the the temp hasn't risen so where is it. Well if you make a hole in the side of the pan the steam will jet out and can do work against a turbine, this is the energy that was given to the water to turn it into steam. The energy is stored in the high pressure steam. To get the same increase of pressure in a gas you would have to heat it to a much higher temperature. We can see how a high pressure gas has stored energy by thinking how we get the gas at room temperature into that state, we would either have to do work to compress it or give it heat energy.