Preview - Energy In Chemical Reactions

Behavior of Individual Molecules

Now you will use the same simulation, but this time you will be observing individual molecules.

 

Directions:

  • Adjust the slider bar to 10 water molecules. Then press "setup" and "go".
  • Now press “add KI” and allow the simulation to run until all KI is split into K+ cations and I− anions.
  • You may repeat the procedure as needed to answer the questions below.

Referenced Questions

These questions were answered in the previous steps. They are provided here for your reference.

Calculate the change in temperature of the system by recording the initial and final temperatures of the system below. (Hover your cursor over the graph to obtain exact initial and final temperatures.)

Questions

Please answer the questions below.

What must occur for an ionic bond to break and KI to separate?

It takes the KI noticeably longer to separate into separate cations and anions here. Describe why this is so.

Calculate the ∆T of the system by recording the initial and final temperatures of the system below. (Hover your cursor over the graph to obtain exact initial and final temperatures.)

Compare your answer to Question 4.3 to your answer for Question 3.1 (referenced again at the top of this page); are the temperature differences identical? Why or why not?

Start the simulation over and press “watch an H2O molecule”. Wait for that molecule to collide with KI. What observation can you make about the relative speed of a water molecule before and after it collides with KI?

Explain why you think the change in relative speed of a water molecule occurs. Where does the energy go?

Based on your observations of the simulation, make a claim of what molecular interaction could cause the kinetic energy of the water molecules to increase (other than simply adding heat to the beaker via a hotplate or flame).

Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.