Freezing Point Depression Lab #2
(Making Ice Cream)Page OneThis lab is an extension of the initial Freezing Point Depression Lab. The major difference being that students were able to use the concept of freezing point depression to freeze their ice cream mixture. The recipe we used is at the bottom of this page.
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From a gallon of milk, pour out ½ gallon milk into another container, to the remaining milk add, 240 mL sugar, 40 mL vanilla extract. Shake it up. Pour 500 mL of the mix into a quart freezer bag (we found the type with the slide closure worked best), squeeze out excess air & seal the bag. Enclose that bag in another quart freezer bag, again squeezing out excess air. Put 1L of snow in a gallon freezer bag, pour in about 100 mL of coarse canning salt, place the double-bagged mixture on top of the snow & salt, add another 500 mL of snow, another 100 mL of salt & seal the large bag (again, squeezing out excess air). Gently, but thoroughly, massage the contents until the ice cream mix gets stiff enough to eat (15-20 minutes). Some of our more coordinated students have been successful tossing the bag back and forth.
EXCESSIVE ROUGH HANDLING CAN CAUSE ONE OR MORE OF THE BAGS TO BURST.
Note: As the snow melts, you may have to add more to keep a constant supply of sub-zero slush in the bag. If more than 500 mL of additional snow is added, more salt may be beneficial.
HAVE FUN!