|I scream! You scream!
We all scream to make ice cream!
Have you ever eaten ice cream that is melting? It melted because it got hotter. In fact, anything solid, like ice cream, melts when it gets hot enough. The temperature at which a solid melts into a liquid is called the melting point. For instance, when solid ice cream reaches its melting point it turns into a sticky puddle of cream. That means that ice cream is just frozen (solid) cream or milk.
Today, we’re doing things backwards. We will take a puddle of cream and make it so cold that it turns into ice cream. You just learned that solids become liquids when they get hot enough. Tell your mentor what you think happens when a liquid gets very cold.
When something gets hotter it absorbs energy, and when it gets colder it loses energy. Because ice is very cold, it doesn’t have much energy. When cream touches ice, energy in the form of heat flows from the cream to the ice. In other words, the cream gets colder and the ice melts. Why doesn’t the ice get warmer? Because the energy from the cream melts the ice instead of heating it up. Remember the last time you drank ice water? The water stayed very cold until the last bit of ice melted, and then it warmed up. That is because energy (from the warm air and table) goes to melting the ice and none heats the water. When you make ice cream, the cream will get colder until it is the same temperature as the melting ice around it and then it will freeze.
Plain ice is not cold enough to freeze cream. What we will do is mix the ice with rock salt. Salt has a special effect on ice: it makes it easier for ice to melt. Because of this, a lot of ice will melt and a lot of energy will be absorbed. Everything will get colder and the cream will freeze. So much energy will be absorbed in fact, that the temperature will actually get colder than the normal freezing point of water!
So now that you understand how cream (liquid) freezes to become ice cream (solid), make your own ice cream and enjoy!!!
Fill the large bag half full of ice and add rock salt. Seal the bag.
Put vanilla, mint, or strawberry, cream, and sugar into the small bag and seal it.
Place the small bag inside the larger one and seal it again carefully.
Shake the bags until the mixture becomes ice cream. (About five minutes)
Enjoy your ice cream!!!
Ice Cream Worksheet
What do you think will happen to the ingredients?
Observations (made during the experiment):
When you first put the ingredients together, what does each ingredient look like?
How does the cream change as time goes on?
What’s happening to the ice?
Conclusions (after the experiment):
What was happening to the cream as it lost heat?
Where was the heat going?
Why do we use salt to make ice cream?
What is your favorite flavor of ice cream?