Whichever day this week that one of the children wasn’t throwing up, an it was 15 degrees outside, we tried an experiment from the book Science Lab in a Supermarket. We filled 3 plastic (well in this case styrofoam) cups with 1 cup water. Marked them "A" "B" "C" and then added 1/8 t salt to "B" and 1/4 t salt to "C" Put them in the fridge for 90 minutes and then started checking them. The book said every 15 minutes but after about an hour that got old, so we started checking every 30 minutes.
The results were very interesting. Cup "A" had no ice at all after the 90 minutes. Cup "B" had some crystals and Cup "C" had even more crystals. Everytime we checked, it seemed like cup "B" or "C" was freezing while cup "A" was doing very little to nothing. So during dinner, I forgot to set the timer and we forgot about them for a couple of hours.
Oh well… didn’t really matter because we saw what we needed to see.
Cup "A" was frozen SOLID. Cup "B" was pretty frozen, but still a little slushy. Cup "C" was VERY slushy.
So now we know why they put salt on the roads when it’s snowing or freezing rain…