Science Buddies: "Ask an Expert"

My project is titled Chemistry of Ice cream making lowering the freezing point of water and I have a few questions. When i did the first test using 2.9 NaCi the freezing point was 0. Does that seem off? My next question was are u supposed to do test #1 - #7 multiple times or just once? Also my test are taking a long time to freeze is that normal ? It’s been about 30 minutes and test #2 still isn’t frozen.

Hi Madison_727,

I’m assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... p013.shtml

The freezing point of your 2.9 g NaCl solution should be lower than the freezing point of your pure water sample. If your water sample froze at 0 deg. C then the salt solution freezing point is too high.

If your solutions are taking too long to freeze your ice bath temperature may not be low enough. The ice-salt mixture in the bath should be close to -10 deg. C during your tests with the solutions. If the bath temperature is not getting low enough, stir the ice-salt mixture or add a little more salt.

My suggestion is to repeat the freezing point tests for the 7 solutions. Three trials for each solution would be even better. Average the multiple trial results for each solution.

I hope this helps. Please post again if you have more questions.

A. Norman