Why does a cup of hot tea cool down so quickly while a flask keeps it warm for a long time? People have been creating insulated containers for centuries to protect food from losing heat. Travelers packed their meals in covered boxes to keep them warm during long journeys. In this activity you will build a simple hot box that aims to keep heat inside for as long as possible.
Concepts Covered
This activity focuses on how heat moves from a hotter object to a cooler surrounding. It highlights the three main ways heat is transferred: conduction through materials, convection through air, and radiation from surfaces. Key ideas include the role of trapped air in reducing heat loss, the effect of material choice and layering on insulation, and how reducing heat transfer helps maintain temperature in everyday objects like flasks and food containers.
Challenge
Safety Instructions
Be careful when handling hot water.
Problem Statement
Build a hot box that can hold a small cup filled with about 200 to 250 ml of hot water. Your box must not exceed the size limit of 10 cm by 10 cm by 10 cm on the outside. A small teacup usually fits within this space, so design your box to comfortably hold one.
You are free to choose any materials you think will help reduce heat loss. You can start with an existing box or build a box from scratch. Try to create a design that closes properly and holds the cup securely. You can experiment with the thickness of your walls, the number of layers you add or the type of lining you choose to improve your design.
Testing Your Design
Fill a small teacup with hot water. Place the cup inside your box and close it. Measure the temperature at the start and again after 15 to 20 minutes. Note the drop in temperature.
If you modify your box, test it again and compare the results to see if your changes helped.
Reflect and Discuss
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What part of your design made the biggest difference in slowing down the temperature drop?
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If you rebuilt your box from scratch, what would you change first and why?
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How does the performance of your box compare with a steel lunch box or a flask at home?
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What real situations depend on good thermal insulation and how is your design similar or different?