Chemical Kim: Holiday Treats
Making carbonated fruit and ice cream is a fun and tasty science activity for kids and adults! Here is an activity that can make the kitchen a very cool and very fun science laboratory this holiday season!
You will need:
Ingredients to carbonated fruit: Cut up fruit, dry ice, bowl and/or pressure cooker
Ingredients to carbonated ice cream: cream (half cream half milk) or whipping cream (heavy cream), sugar, vanilla, and flavorings (or melted ice cream),
stainless steel mixing bowl, wooden spoon, gloves, safety glasses, carbon dioxide, strong heavy mixing bowl
Now try this (fruit):
1. In bowl place small pieces of dry ice.
2. Mix in cut up fruit pieces for 10 minutes.
3. As the dry ice sublimes (turns to a gas) the fruit becomes carbonated.
4. Optional: Using a pressure cooker place pieces of dry ice on the bottom of the cooker. On mess rack place fruit pieces on top of the dry ice. Cover the pressure cooker with release valve open to allow pressure from gas to escape. After 30 minutes to an hour open and enjoy the fizzy fruit.
Now try this (ice cream):
1. In the stainless steel mixing bowl combine ½ cup cream, ¼ cup vanilla, ¼ cup sugar and flavorings and mix well.
2. Wearing gloves and safety glasses, slowly add crushed dry ice the cream mixture (making sure the dry ice pieces are extremely small).
3. Continue to mix while adding dry ice as needed until the cream freezes to the consistency wanted and all of the dry ice has undergone sublimation (you will see no more "fog" emitting from the mixture).
4. Have an adult inspect to make sure no more dry ice remains and then you can grab your spoon, eat and enjoy.
5. Your ice cream is carbonated!
Dry ice is solid carbon dioxide and at room temperature undergoes a phase change called sublimation. Sublimation is the process of changing from a solid to a gas without going through the liquid phase. To make carbonated drinks and foods gaseous carbon dioxide has to dissolve in water. Thus, as the dry ice sublimes, the carbon dioxide gas dissolves in the water in the fruit, making a very fizzy tasty treat.
To make ice cream the cream mixture needs to change from a liquid to a solid. This process is called freezing (a phase change) and requires heat to be removed from the mixture. Because ice cream is primarily water it needs to reach temperatures of 0OC or lower. Dry ice is solid carbon dioxide that is at a temperature of -78.5OC (-109.3OF), that is far below the freezing point of ice cream. That temperature is so extremely cold that it will freeze solutions with water in a matter of minutes. Also in using the dry ice carbon dioxide gas is dissolving in the water and thus carbonating your ice cream!