The Chill Test: Water in Coloured Cans
Activity 3.11: Cooling of Water in Different Coloured Cans helps students understand how colour affects heat emission and retention. It’s a continuation of the previous activity (3.10) but focuses on the cooling of water in cans painted black and white.
Objective
To observe how water cools down in cans of different colours and understand the thermal properties of these colours.
Materials Needed
- Two identical tin cans (one painted black and the other white, from Activity 3.10)
- Hot water
- Thermometer (optional)
Steps to Follow
- Prepare the Cans: Use the same black and white painted cans from Activity 3.10.
- Fill with Hot Water: Pour the same amount of hot water into each can. The starting temperature should be the same, ideally around 60°C.
- Place in Shade: Put the cans in a room or a shaded area.
- Wait and Measure: After 10-15 minutes, measure the temperature of the water in both cans. If you don’t have a thermometer, you can use touch (carefully) to determine which can have cooler water.
Expected Observations
- The water in the white can may cool down faster than in the black can.
Understanding the Concepts
- Heat Emission and Retention: Black absorbs heat when it’s hot and also retains it longer when cooling down. On the other hand, white, which reflects heat, also tends to lose any absorbed heat more quickly.
- Practical Implications: This is why dark-coloured objects or clothing feel warmer in the sun and stay warm longer, while light-coloured ones are cooler and don’t retain heat as much.
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Conclusion
This activity shows that the colour of an object not only affects how it heats up but also how it cools down. Dark colours like black retain heat for a longer period, while light colours like white emit the heat more quickly. This experiment provides a clear understanding of the thermal properties of different colours, which is essential in many real-world applications, such as choosing clothing for different climates and designing energy-efficient buildings.
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