You never want to touch a hot car or lick a cold metal flag pole because metal conducts heat. But are all metals the same? Is there a huge difference between one type of metal or another? Why do we use copper bottom pots or iron skillets? This activity will show the difference in conduction between three types of metals, iron, copper and aluminum. This activity is fairly quick but very fun and packed with physics. It's also quite tasty!
Student Guide
Meltdown
An exploration of using metal to melt chocolate
How do different metals conduct heat?
This resource was originally published in PhysicsQuest 2011: Spectra Heats Up!
How do different metals conduct heat?
- Hershey's kisses (3)
- 1 steel wire
- 1 copper wire
- 1 aluminum wire
- Hot water
- Cup
- Tape
- Stopwatch/watch with second hand
Intro
Before the experiment
How many different types of metal can you think of?
- What are some of the differences between all of these metals?
What does it mean for something to be ‘hot’ and ‘heat up’?
How can you tell if chocolate has melted?
Predict which metal you think would conduct heat best, steel (mostly iron), copper, or aluminum. Think about where you have seen these metals before and what they are often used for when making your predictions.
Setting Up
Unwrap 3 Hershey’s kisses.
Skewer each kiss with one of the three metal wires. It is easiest to go through the middle of the bottom and out of the top. There are extra kisses in case one or more break during this process (Figure 1).
Figure 1Tape the wires to the inside edge of the cup, kiss end up. There should be two inches between the lip of the cup and the bottom of the kiss (Figure 2).
Figure 2
During the experiment
Collecting data
Fill the cup with hot water and start the stopwatch. Make sure the water is high enough to cover the bottoms of the wires. **Stop after 2 min even if all kisses have not yet hit the water.
- Record the time it takes for each kiss to fall into the water
Aluminum _____seconds
Steel _____ seconds
Copper _____seconds
Analyzing data
What were your results?
- What happened when the hot water was poured in the cup?
List them in order of their ability to conduct heat, from highest to lowest (1 means it conducts the best).
Aluminum _____ Steel _____ Copper _____
How did this compare to your predictions?
Conclusion
Did all the kisses melt and slide down the wires? If not, why do you think they didn’t?
When would you want to use _________________ (choose a metal)?
When would you want to use _________________ (choose a metal)?