Water molecules are attracted to each other, causing them to move toward each other, due to weak van der Waals attractions.

Why are steam burns particularly dangerous?

1. When you run the first model below by clicking on the Run button below the model, the two water molecules initially have no kinetic energy.
2. Observe the two graphs to the right of the model. The small triangle that appears on the right edge of a graph when the model runs indicates the average value for that graph (either Kinetic Energy or Potential Energy).
3. Note where the triangles are when the model starts to run, and then run the model for at least a minute and see how the position of those triangles (or the average values for Kinetic Energy and Potential Energy) change when the molecules get closer together.

1. Now you see the second model below of the several water molecules as they spread apart from each other. When you run the model by clicking on the Run button below the model window, the molecules will be allowed to condense (come together in a more dense phase).
2. Notice what happens to the potential and kinetic energies when you run the model.

1. In the first model, when do the water molecules have the most potential energy?
2. In the first model, what relationship do you notice between the kinetic energy and potential energy?
3. In the second model, what did you temperature changes did you observe as the water molecules condensed?

What did you observe, and why does this help explain why steam can cause serious burns?

Steam burns are particularly dangerous. To understand why consider the following:

• When water is a gas the molecules are all spread out like the way the water molecules started in the above model.
• If you put your hand in the steam, the water molecules will condense onto your skin, getting closer together, just like the water molecules above do when you run the model.
• Kinetic Energy/Particle is actually the same thing as temperature, so the Kinetic Energy graph above is really a measure of temperature.

Run the model again. Relate the Kinetic Energy to the Potential Energy to the phase change to further explain why steam burns are so dangerous.