To see water turning into steam, just boil some water in a pot (with permission from an adult). When it boils, do you see the steam? What does the steam do? Why?
Try punching a hole in an aluminum pie pan and putting it over the steaming pot (Wear oven mitts). What happens to the steam? Now take the pie pan off the steam (tilting it towards you to shield yourself from the steam so you don't get burned). Punch another hole and try it again with two holes, then three and four. What difference do you see?
If you have the kind of kettle that whistles, that's because when the water inside the kettle boils, it turns into steam. The steam is crowded inside the kettle and tries to find a way out, but the only way is through the little hole of the whistle. When the steam pushes its way through the whistle, it makes the whistling noise to let you know that the water has boiled and it's time to pour your tea.
To find out more about steam, check out these books from Amazon.com or from your library: