My son is in fifth grade and has selected Supercooling water as his science project. Once the ice is in the bowl and the salt has been placed on the ice, should he stir the water in the cup periodically? The thermometer sits at an angle so it is measuring the temperature of the water that is closest to the ice. Or should we use something to cause the thermometer to stand upright in the center of the cup?

I just read the description of this experiment. It sounds like it will be quite interesting.

I'm glad, as a parent, you are getting involved in your student's science education. That's great!

Your idea of periodically stirring the water is a good one. It will certainly distribute the heat in the water mover evenly, and give a better average reading on the temperature. Your concern about the thermometer being closest to the ice, and possibly affecting the temperature reading is a valid one.

I would suggest running the experiment 2 ways, using multiple trials in each method. One is exactly the way described in the procedure, with a minor difference. I think it would be a good idea to leave the cardboard cover on the cup of water, but pierce a hole in it, one that can snugly hold the thermometer, and then use it to suspend the thermometer sensing bulb in the center of the cup. That would eliminate the possibility of the thermometer being affected by its close proximity to the ice.

Then I would suggest running the experiment again, still using the cardboard cover, by pushing the thermometer in all the way so that the sensing bulb is close to the ice, just as if you had not been using the cardboard cover at all, and periodically stirring the water. This will affect the rate at which the water cools, and probably affect your observations about the super cooling temperature. That's because it will affect how ice crystals grow in the water - an affect you should also see when using the different water types/treatments mentioned in the experimental procedure.

I hope this answers your questions and that you and your son HAVE FUN WITH SCIENCE!