Thoroughly mix a pint of whole milk, a pint of light cream, a can of sweetened condensed milk and a teaspoon of vanilla extract in gallon jar. Pour one cup of the mix into a pint-sized glass jar. Place the glass jar inside a gallon freezer bag and place the freezer bag inside a large coffee can. Pour ice cubes and rock salt into the bag and seal it, leaving some air in the bag around the jar. Place a lid on the coffee can and seal it with duct tape. Roll the can around on the floor for 30 minutes. Unseal the coffee can and remove the bag. Rinse the jar off with cool water and sample the contents. Adaptations include placing only ice in one bag and the rock salt and ice mix in another bag or rolling one can and leaving a second can still to see how it affects the jar contents.
Compare the speed at which various liquid freeze. Place one jar inside one freezer bag for each liquid and mark the contents of the liquid on the freezer bag. Remember to leave space at the top of each jar so the expanding liquid doesn’t break the jar. Suggestions for jar contents include 150-degree tap water, refrigerated tap water, room temperature commercial saline solution and a mixture of one part water to one part alcohol. Have students check the jar contents every 30 minutes and record which liquids freeze faster.
Air pockets can provide an insulating effect. Place a seedling inside a small freezer bag and suspend the bag inside a glass jar by taping a corner of the bag to the lid. Place the jar inside a freezer bag and blow additional air inside the bag before sealing it. Take a second seedling and set it inside a glass jar without a bag around the seedling. Place the jar inside a freezer bag and remove as much of the air as possible when you seal the bag. Place both bags in the freezer and monitor the health of the seedling. Determine whether the extra air cushion protects the seedling.
Cold temperatures can make things more brittle. Place a thin-sided glass jar inside two sealed freezer bags and a similar glass jar inside another set of sealed freezer bags. Freeze one jar and leave the other jar at room temperature. Remove the first jar from the freezer after 24 hours. With the jar still inside the two freezer bags, tap the side of the jar with a small hammer. Tap the jar at room temperature with the same force. Compare the brittleness of the jars by examining which breaks easier and the relative size of the broken glass pieces.