Chilly Ice Cream
The purpose of this lab was to make ice cream using ice and salt put into a gallon sized freezer bag and then putting the ice cream ingredients into another bag which would then go into the larger bag. The dependent variable would be the temperature and the dependent variable would be the time. The results should show that
For ice to melt, it has to get heat from something. In our ice cream project, it gets the heat from the ice cream mixture (and from your hands, which is why they get cold while holding the bag). When the ice is melting, it is at 0 degrees Celsius. When ice is melting, the surface of the ice is wet. At the surface, there is solid ice on one side, and liquid water on the other. The surface is exactly at the freezing point. This means that some water molecules are leaving the ice and moving into the water, but it also means that some liquid water is refreezing onto the ice. At equilibrium, the heat lost by the water as it freezes is equal to the heat gained by the ice as it melts.
Because plain ice can only barely cool something to the freezing point of water, we will need to do something to make it much colder than that, since our ice cream mixture freezes at a lower temperature than water.
The ice cream freezes because the salt and the ice mix to make a substance with a lower freezing point than ice alone. This means that the ice and salt mixture must get even more heat from somewhere in order to melt.
Salty water freezes at a lower temperature than plain water. But the ice is made of plain water, so it melts at 0 degrees Celsius. Since the ice keeps melting, but the water no longer freezes (because there is only salt water, which doesn't freeze at 0 degrees), the temperature goes down.Proxy-Connection: keep-alive Cache-Control: max-age=0 r>The heat gained by the ice as it melts is no longer offset by the heat given up by freezing water (since the water is no longer freezing back onto the ice)....