Which Thermodynamics Demo Best Illustrates the Laws of Energy?

[The28]

So I need to give an exciting thermodynamics demo based on one of the first two laws. I have found it difficult to either make it exciting enough or to make it apply to thermodynamics enough.

I have a few that I have come up with but I don't think any really apply as well as I want.

1)Can crush but on a bigger scale with like a drum. Heat water in a can and then dunk it in cold water. (shows that heat flows from hot to cold 2nd law)
2)Spud gun. Giant spud gun but that's see through. Ignite gas and fire potato (Add heat and show that work is done on the potato 1st law)
3)Boiling water and liquid nitrogen. Nitrogen evaporates and makes a huge cloud due to condensing water from the air (2nd Law showing that heat again flows from hot to cold and energy is dissipated)

Are any of these any good?

Could do with some help.

 

[jfizzix]

Depending on your budget, you could get one of those coffee cup Stirling engines. Last time I checked, you can find a nice one for less than 100 bucks. They run off the temperature difference between the hot coffee and the comparatively low temperature surroundings. Also, you can make the engine run faster by putting an ice cube on top of it (i.e., by increasing the hot-cold temperature difference).

If you have a vacuum pump, you can freeze liquid nitrogen, or just freeze water through evaporative cooling. With the vacuum pump, the most energetic molecules will escape the liquid and be pumped out, lowering the average internal energy of the liquid, cooling it down, until it freezes.

 

[martane]

Hi there! I think all of your ideas are great and could definitely make for an exciting thermodynamics demo. However, if you're looking for something that applies more directly to thermodynamics, I have a suggestion.

How about demonstrating the concept of entropy? You could set up two identical glasses of water, one at room temperature and one heated up. Then, you could pour the heated water into a container with a divider, so that one side is hot water and the other side is cold water. As the hot water cools down, you could observe and measure the temperature of each side. This would show how the hot water loses energy and becomes colder, while the cold water gains energy and becomes warmer. This demonstrates the second law of thermodynamics, as heat flows from the hot water to the cold water until they reach an equilibrium.

You could then take it a step further and add food coloring to the hot water before pouring it into the container. As the hot water mixes with the cold water, the food coloring will spread and the colors will become more and more diluted, showing how entropy increases as the system reaches equilibrium.

I hope this idea helps and good luck with your demo!