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Ice Cream in a BagPennsylvania Academic Standards: Science and Technology 3.4.7 A
Did you know that delicious bowl of ice cream you just made is a rather complex scientific experiment? Making ice cream involves changing the state of the cream mixture from a liquid to a solid. There are three states of matter we see on Earth: solid, liquid, and gas. A gas that loses enough heat turns into a liquid. A liquid that loses enough heat freezes into a solid. See if you can answer the following question using the Internet or your science textbook.
Facts:
- Freezing point is the temperature at which freezing of a substance occurs.
- The freezing point of the cream mixture is 14 degrees F
- The freezing point of water (ice) is 32 degrees F
Question: How does adding rock salt change the freezing point of ice?
Answers: Show/Hide
Adding the salt to the ice does three things:
Since melting requires energy, heat gets stolen from the salt/ice/water mixture, making it colder than it was without the salt. If the mixture gets down to 10 degrees F, the ice cream chills down past its own freezing point (14 degrees F) and turns into a solid ice cream.
- It lowers the freezing point of the water to approximately 1degree F.
- It melts some of the ice in the bag.
- It lowers the temperature of the salt/ice/water mixture.
Since melting requires energy, heat gets stolen from the salt/ice/water mixture, making it colder than it was without the salt. If the mixture gets down to 10 degrees F, the ice cream chills down past its own freezing point (14 degrees F) and turns into a solid ice cream.
Information adapted from: Flash! Bang! Pop! Fizz! Exciting Science for Curious Minds by Janet Parks Charhrour, copyright 2000, published by Barron's Educational Series, Inc.
Funding provided by The Erie County Department of Health & The Pennsylvania Department of Health