Kick the can and end up with a delicious, cooling treat

What would summer be like without ice cream? Yes, there are many delicious brands in the store, but I am still a strong supporter of homemade. There really is nothing better than the smooth velvety texture of homemade ice cream while you are sitting outside on a hot summer day. I know it sounds hard, but it is super easy when you enlist the help of those little scientists in the house! Let’s get started!

*Remember to ask an adult before you do this experiment.

Materials

- two coffee cans – one large and one smaller so it will fit in the large one - duct tape - ice - coarse (pickling) salt - measuring cups - measuring spoons - sugar - heavy (whipping) cream - milk - vanilla - mixing spoon

Procedure

1. Place the small coffee tin inside the large tin.

2. Pack ice evenly between the two cans about 3/4 of the way up the sides.

3. Measure 175 mL (3/4 cup) milk into the small can.

4. Measure 250 mL (1 cup) of heavy cream. Pour into the small can.

5. Add 80 mL (1/3 cup) sugar. 6. Stir well. 7. Add 5 mL (1 tsp) of vanilla.

8. Make sure this is combined well and the sugar has been dissolved. You may have to stir it for a bit.

9. Put the lid on the smaller coffee can and secure in place with duct tape.

10. Fill the rest of the large coffee can with ice. It should be all the way up the sides and perhaps on top of the small can.

11. Sprinkle 250 mL (1 cup) salt over the ice.

12. Put the lid on the large can and secure with duct tape also.

13. Shake, kick, and roll the can for at least 15 minutes and then check.

14. If the ice cream is not hard yet, you may have to add more ice and salt and shake some more. Make sure you put the lid back on!

15. Enjoy!

What is going on?

The same reason many cities use salt on icy roads in the winter is why we are using salt with the ice to make ice cream. As you know, salt makes ice melt. When the salt and ice mix, the freezing point of the ice is lowered causing the ice to melt. Where is the heat coming from to cause the ice to melt you might wonder. Well, the heat that causes the ice to melt in this case is from the warmer cream mixture in the other container. This is why you have to keep shaking or kicking the can — by shaking the mixture up, you are continually moving the warmer cream mixture from the middle of the can to the outside where it can begin to freeze evenly. By lowering the temperature that the ice freezes in our container, we are able to create temperatures below 0 C which is necessary for the cream mixture to freeze into delicious creamy ice cream.

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.