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# Surface Area and Melting Rate: A Study

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Source:
Author: Janice VanCleave

Category: Physics—Energy—Heat

Project Idea by: Declan Morgan

Question: How Does a Refrigerant's Surface Area Affect How Well It Cools?

Temperature is the measure of how hot or cold a material is. Heat is the energy that flows from a warm material to a cool material. For a material's temperature to decrease, it must lose heat. For a material to increase in temperature, it must gain heat.

A refrigerant is a material used to cool other materials. Ice is a refrigerant that owes its effectiveness to the fact that it stays at its freezing temperature of 32°F (0°C) until it absorbs enough heat to melt.

Surface area is the size of the surface of an object. Surface area increases with the subdivision of the material. For example, crushing and grinding a solid will increase its surface area. A project question might be, "How does a refrigerant's surface area affect how well it cools?"

Design a way to measure the effectiveness of a refrigerant such as ice. One way is to determine how fast ice cream melts when it's put in contact with ice having different surface areas such as different sizes of crushed ice and cubed ice. A measured amount of ice cream can be placed in a cup and surrounded by one form of ice. After a predetermined time, measure the amount of melted ice cream. To measure how much has melted, pour just the liquid into a measuring cup. Use the same amount of refrigerant for each test.

• Independent Variable: Refrigerant's surface area
• Dependent Variable: Effectiveness of refrigerant determined by amount of melted ice cream
• Controlled Variables: Amount of ice cream, amount of refrigerant, containers, increments of time, measuring device
• Control: Ice cream not surrounded by a refrigerant

### Other Questions to Explore

1. How does insulating material affect a refrigerant's effectiveness?
2. How does the thermal conductivity of a material affect cooling or heating it?
3. Are gel ice packs better refrigerants than ice?