Expert: Daniel Mazur - 8/9/2010

Question
Hello my son has bought home an assignment. He is grade 6 ,
12  years old in Australia.  He has to present 6 to 8 photos
showing clear and dramatic phases of change from one state
to another.  he only has 2 weeks to complete.  Do you have
any ideas for what something coulld be that he can track
changes? Thankyou so much.

Answer
Dear Mrs. Davis,

the phase changes accessible to taking photos of are the boiling (from liquid to vapour), condensation (from vapour to liquid), freezing (from liquid to solid) and melting (from solid to liquid). It is a bit hard to capture sublimation (from solid directly to vapour) and desublimation (from vapour to solid).

The best bet is the ice-water-water vapour changes. Melting ice cube on a tabletop, water boiling in a kettle and the steam streaming out of its nozzle, droplets of condensation on the bottom side of a lid on top of a pot of soup being cooked, icicles forming in a freezing weather around a running stream in the countryside, the frost "paintings" on the outside of windows in winter. In addition to that, wax dripping off of a burning candle is easy as well. I trust your son can think of variations to this theme to get more pictures - melting ice cream in a direct sunlight, for example, "steaming" dry ice, if you can get some... There are a few options.

Granted, these changes are not dramatic, but they are suitable to a school assignment like that and I think this is what was asked for.

Good luck to your son!
Daniel