This material is replicated on a number of sites as part of the SERC Pedagogic Service Project
- water vapor;
- a mechanism for cooling;
- condensation nuclei.
Context for Use
This site contains:
- Construction and use photographs;
- What to do and what to notice;
- Detailed scietific backgraound;
- Time required for construction (5 minutes) and use in class (15 minutes).
Teaching Notes and Tips
An alternative, light weight, and durable demonstration that I (R. MacKay) use includes a clear 2-liter plastic soda pop bottle with lid, water, and incense (or just a match). I like the incense to add a little drama and humor to the demonstration. To make a cloud, put several table spoons of water in the bottle, shake it around a bit, two seconds worth of incense smoke, and screw the lid tightly on. Squeeze the bottle tightly and then release rapidly. After a few repetitions a cloud appears when the pressure is released and disappears when the pressure is applied (bottle squeezed). It is more fun and interesting if you don't put any smoke in the bottle to begin with and pretend that your demonstration fails. If students have read the chapter or understood what you told then 10 minutes before they will remind you that you need some condensation nuclei. I also use this in other classes where the concept of adiabatic cooling from expansion or adiabatic warming from compression are discussed. I like it because it always works, is easy to set up, and generates student interest.