Molarity

The title of the Project: Molarity

This virtual laboratory is intended for use in chemistry classes on the following topics:

  • 8th grade. Chapter X. “Solutions and solubility”

Objectives:

  • to visualize the relationship between solute amount, solution volume, and concentration
  • to introduce the molarity formula 
  • to explore solubility limits of different solutes

Practical part

1.Launch the simulation. A beaker containing a solution will appear on the screen. You can select the solute you want to investigate from the dropdown menu.

2.On the left side of the beaker, you’ll find two sliders. These sliders allow you to adjust the amount of solute and the volume of the solution by dragging them up and down. As you manipulate the sliders, pay attention to the red arrow on the right side. This arrow represents the concentration of the solution and will change accordingly. You might also notice the color of the solution becoming more or less intense as you adjust the amount of solute.

3.Check the “Solution Values” box to see the number of moles of solute and liters of solution.

4.Select a solute from the dropdown menu (e.g., drink mix, copper sulfate).Use the slider to add or remove solute and observe the solution’s color intensity.

5.Use the other slider to adjust the volume of solution.Watch how the concentration changes with adjustments.

6.Spend some time exploring. Try changing both solute amount and solution volume. Analyze the patterns. How does the amount of solute and solution volume affect the color intensity and concentration?

7.Based on your observations, try writing a mathematical formula for calculating molarity that relates:

  • Moles of solute
  • Liters of solution

8. Experiment with different solutes. Use your formula to predict the concentration for a few cases.Verify your predictions by checking the actual concentration in the simulation. Does your formula hold true?

9.Notice how each solute has a maximum concentration it can reach in the solution. This concept is called solubility. You can explore this further with PhET’s “Concentration” simulation.

Conclusion

The “Molarity” simulation is a valuable tool to understand solution concentration. By following these steps and exploring the simulation, students can learn how the amount of solute, solution volume, and concentration are interconnected.