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Lesson 2-The Dose Makes the Poison boy looking through a microscope
Dose-Response Relationships

Description of Dose-Response Seed-Germination Experiment

In this first section of the Dose-Response Seed-Germination Experiment, you'll figure out the amount of chemical you'll need to make 20 milliliters of solution in each of 6 required concentrations. A table displays the amount of water (column 1) and the required concentration in each solution (column 5). With the numbers you are given in columns 1 and 5, you'll need to decide how much of the chemical you'll need to meet the required concentration and enter that amount in column 2. Once you've entered an amount in column 2, the total volume of liquid and the concentration of chemical will be calculated for you in columns 3 and 4. A large checkmark will appear to the right of column 4 if you enter the amount of chemical necessary to reach the required concentration. An overflowing beaker will appear if you enter too much chemical, and no image will appear if you don't enter enough chemical.

In row 1 of the table, you are given 20 milliliters of water (column 1) and 0% for the required concentration (column 5). Enter the amount of chemical in column 2 needed to make 20 milliliters of solution. The total volume of liquid and the concentration of chemical will be calculated for you in columns 3 and 4.

You'll want to do the same—enter the amount of chemical and check the results—for the next 5 scenarios:

In row 2, you are given 18.75 milliliters of water and 6.25% for the required concentration.
In row 3, you are given 17.5 milliliters of water and 12.5% for the required concentration.
In row 4, you are given, 15 milliliters of water and 25% for the required concentration.
In row 5, you are given, 10 milliliters of water and 50% for the required concentration.
In row 6, you are given, 0 milliliters of water and 100% for the required concentration.

Once you finish this section, click on the "Reset" button below the table to start the exercise over or click the "Do Experiment" button to go to the second section of the activity.

In this second section, you'll see that the concentration of chemical within a solution affects the number of seeds that sprout within that solution.

First, you'll choose a chemical from the menu shown at the top of the window. Click and choose from one of the following: fruit-punch soda, plant fertilizer, or window cleaner.

Next, click the test button in row 1 of the table shown below the pull-down menu. The test button is located in column 1, just to the right of the chemical concentration. The chemical concentration for the chemical you chose from the pull-down menu is set at 0%.

Once you click on the test button, a certain number of seeds, pictured in a solution-filled Ziploc bag at the bottom right-hand corner of the screen, will sprout. You'll want to count the number of seeds that did not sprout. (This represents the number of seeds that will not grow in a solution of 0% of the chemical you chose.)

Enter the number of seeds that did not sprout in column 2 of row 1. The percentage of seeds that did not sprout will be automatically calculated for you in column 3.

You'll want to do the same—click the test button, count the seeds pictured in the Ziploc bag, and enter the number of seeds that did not sprout—for the next 5 scenarios:

Row 2: concentration of chemical is set at 6.25%.
Row 3: concentration of chemical is set at 12.5%.
Row 4: concentration of chemical is set at 25%.
Row 5: concentration of chemical is set at 50%.
Row 6: concentration of chemical is set at 100%.

To see how different chemicals affect seed sprouts, reset the activity (the "Reset" button is at the bottom of the window), choose another chemical from the pull-down menu, and perform the exercise again.

Once you finish this section, click on the "Back" button, located below the table to the right of the "Reset" button, to go to the first section, or click the Exit button to quit the activity.

Data tables