Workout: Interatomic forces

Read

Read the web page Interatomic forces.

Launch

To give you some sense for how this works, go to the CLUE (Chemistry, Life, the Universe, and Everything) simulation.

Set up

The first page shows the interaction of two neutral inert gas atoms. We know that a charged object (like an ion) will polarize a neutral object (like an atom). We also know that the charges in a neutral atom are continually moving around and fluctuating. 

Answer these questions

1. Explain why two neutral atoms attract each other. 
2. Click on the blue "next" box in the upper right of the page. Page 2 shows two atoms and a graph of the potential energy of their interaction. Explain what is happening.
3. Click on the blue "next" box in the upper right of the page. Page 3 shows two atoms and a graph of the potential energy of their interaction. The red bars on the right show the potential and kinetic energies of the atoms. Note the black horizontal bar in the middle of the total (potential + kinetic) energy bar. This represents a total energy of 0. Move one of the atoms so that the total energy is negative. Release it and describe what happens. Then reset and arrange the atoms so that the total energy is positive. Describe what happens. 
4. Click on the blue "next" box in the upper right of the page. Page 4 shows a Van der Waal's bound atomic pair in the context of multiple other atoms. atoms. A graph on the lower right shows the (log of the) number of atoms having different kinetic energy. The energy needed to dissociate the bound atomic pair is shown by a vertical line. Raise the temperature arrow (the green arrow in the vertical blue bar at the right) to degrees Kelvin.
5. Despite the fact that many atoms have enough KE to break up the bound pair, it can take a very long time and a lot of collisions before the pair gains enough energy to separate. Why do you think this is?

Joe Redish, Fall 2016