Materials

• An html5 compatible device: iPad or computer
• Pencil
• Printed worksheets or scrap notebook paper for writing
• Scenario Cards Worksheet
• Concentrating on Concentration Worksheet
• Questions

Directions

On your laptop or computer go to Phet: Concentrations ©
https://phet.colorado.edu/sims/html/concentration/latest/concentration_en.html

1. The pieces in the photo that are boxed in purple are movable and will alter your amount of concentration or solution.
2. Move the concentration sensor into your solution before beginning. In the image it is the piece with text beside it saying that it moves.
3. Add a couple shakes of “drink mix” to the water then take a couple minutes to see how the moving parts work and affect the concentration of the solution.
4. Hit the restart arrow when you are done experimenting.
   1. Don’t forget to add your concentration sensor.
5. Once again, add a couple shakes of drink mix to the water and fill in the remaining boxes of the table:
6. Hit the restart arrow when you are done completing the chart.
7. Change the “drink mix” to one of your other solute options. Remain on the solid setting and add as much as you can. Answer the questions below:
   1. How do you know when a solution is saturated?
   2. When a solution is saturated, and additional solid solute is added, what happens?
   3. How does adding this additional solute change the concentration of the saturated solution?
   4. How does evaporation change the concentration of a saturated solution?
8. Hit the restart arrow and add your concentration sensor.
9. Choose a new solute and move from a solid to a solution.
   1. How can you measure the concentration of the solution inside the dropper?
   2. How might you get that concentrated solution to become saturated?
   3. Does it work?
   4. Do you think it would work for other solutions? Yes or No Why or why not?
      e. Are the concentrations of all of the solutions the same?

Brainstorming

1. Create a list of where we would see solutions being prepared or used in the agricultural world. Challenge yourself to come up with at least 10 different applications of solutions in agriculture.
2. Next watch how solutions are used as chemical sprays for herbicides in Peterson Farm Brothers © video on Chemical Application.
   1. As you watch, focus on how the solutions are mixed in the spraying tank but also on how the
      applicator is precisely applying the spray so that there is a control on how much spray is being used
      in one area.

Compare and Contrast Home Use vs. Commercial Use

Using the scenario cards provided, work through exactly how much of the active ingredient (solute), in this case glyphosate, is being sprayed per square foot of land for each scenario. See PDF of lesson for printable cards.

Questions

Questions as PDF

Based on the data collected and analyzed above, answer the following questions.

1. List at least two ways the home use and the farm use products are different.
2. Why did all of the units need to be the same on our calculations?
3. How are home application and farm application likely to be different? (Hint: Think back to the video, what tech do farmers have?)
4. Based on the evidence seen above, are you surprised by any of the numbers you calculated? Did it seem more or less than you anticipated?
5. Based on this particular set of data, how do farmers and homeowners compare in their use of the chemical glyphosate. (Include the terms, area, active ingredient, and concentration in your answer.)

Answer Key

PDF of Answers