This web site uses JavaScript to dynamically create content. Please ensure your browser supports JavaScript.
Chemicals, the Environment, and You
National Institute of Environmental Health Sciences Home
skip navigation Main Getting Started Teacher's Guide Student Activities About NIH and NIEHS
glossary | map | contact 
Teacher's Guide - return to teacher's guide home hand using a mouse

Lesson 4-Individual Responses Can Be Different


Activity 1

If necessary, fill the 3 beakers from Lesson 2 with equal amounts of water. Add 1 drop of the mystery chemical to Beaker #1, 4 drops to Beaker #2, and 16 drops to Beaker #3.

3 identical beakers filled with equal amounts of water, and 3 containers of different sizes filled with different amounts of water

Collect 3 clear containers of different sizes and label them #1, #2, and #3. Fill each container with water, making sure that each container holds obviously different amounts of water, with #1 having the least and #3 having the most.

Make a transparency of Master 4.1, Acetaminophen Dosage Chart.

Activity 2

Decide whether you will use the Web site or print version of this activity. If you choose the Web version, arrange for students to have access to computers.

If you use the print version, conduct the activity with the whole class. Later, let students review the problem using the Web site on their own at a computer center. Make a transparency of Master 4.2, A Poisonous Dose? The Case History. Duplicate Master 4.3, A Poisonous Dose? The Problem, 1 for each student.

Activity 3

At least one week before conducting Activity 3, send home personalized parent letters (Master 4.4, Parent Letter) to inform parents of the investigation and to get permission for the students to consume a caffeinated soft drink during science class. You can use the letter to ask each student to bring in his or her own can of the designated caffeinated soft drink.

Arrange to have enough cans of the same kind of caffeinated soft drink for each student who participates in the investigation. There are several ways to do this:

Before the day of Activity 3, have students practice taking a resting heart rate so they are used to finding their pulse, counting the beats for 15 seconds, and multiplying the number they count by four to get a resting heart rate for one minute (see Activity 3).

Duplicate Master 4.5, The Chemical Caffeine: How Do You Respond?, 1 for each student.



1. Ask students why they think toxicologists look at both whether a chemical has an effect on living things and what happens at different doses. Why do students think it matters to look at doses?

teacher demonstrating activity 1Students may bring up the term overdose, which refers to a situation in which a person receives too much of a particular chemical, usually a drug. Students should realize that the proper dose of a chemical is what makes it beneficial to people and that knowing the dose is useful in determining the appropriate human consumption of that chemical. Some chemicals, such as vitamins and minerals, are beneficial at a particular dose, but human health suffers if the chemicals are present in high or very low doses (you can have too much or not enough). Other chemicals, such as drugs and pesticides, usually are more harmful as the dose increases.

2. Tell students that you are going to demonstrate one reason why paying attention to dose is important in the study of toxicology.

3. Ask students to observe the three new containers and compare them with the setup of the demonstration from Lesson 2. Discuss their observations by asking questions like these:

4. Keep the containers of water on the desk while you display the transparency of Master 4.1, Acetaminophen Dosage Chart. Ask questions such as these to discuss the concept of dose with respect to body size:

Acetaminophen dosage chartD

National Science Education Standards icon Content Standard F:
Students should develop understanding of personal health.

5. Tell the students that size is one difference in people that can effect how susceptible they are to chemicals. Ask students what other factors about an individual might make the individual more or less susceptible to chemicals such as acetaminophen. List the factors on the board.

Start the list with size (weight). Other factors that can affect susceptibility to chemicals are age, lifestyle or behavior (such as being an alcoholic), gender, genetics, and general health.

6. Tell students that toxicologists know that these variable factors determine an individual's susceptibility to the effects of environmental toxicants. Write individual susceptibility as the title of the list you made on the board in Step 5. Tell students that, because of their understanding of individual susceptibility, toxicologists expect that individuals may respond differently to the same dose of a chemical.

three police officers
Photos: Corel
African children elderly Native American woman

7. Ask students to apply the concept of individual susceptibility to their observations of the seeds in their investigation. If students need help, prompt them with questions such as these:


The following procedures describe how to conduct the Web version of this activity, which is the preferred method of instruction. Instructions for the print version follow.

Web activity iconUse a computer lab where you can set up multiple computers. Open the Web site in your browser (see instructions for using the Web site). From the main page, click on Web Portion of Student Activities, then select Lesson 4—Individual Responses Can Be Different. Start the activity by watching the video. Encourage students to work in pairs to solve the problem.

Print Version

If your students do not have access to computers equipped with the Internet or you would like an opportunity to assess students individually on their understanding of a toxicology problem involving humans, use the following print version of Activity 2.

1. Display the first page of the transparency you made from Master 4.2, A Poisonous Dose? The Case History. Read the transparency with the students.

2. Distribute copies of the first page of Master 4.3, A Poisonous Dose? The Problem. Ask students to work in teams of three to complete Part I. Circulate around the room to help students read the dosage chart, understand the math, and draw some conclusions.

Students should select letter e: Both b and d are correct. Andy received 1 teaspoon four times a day, or 4 teaspoons in all. Because there are 6.25 dropperfuls of acetaminophen in each teaspoon and 80 milligrams of acetaminophen in each dropper, the calculation of the amount of acetaminophen Andy received from his aunt should read:

this is an eqaution: 4 teaspoons multiplied by 6.25 dropperfuls divided by 1 teaspoon multiplied by 80 milligrams divided by 1 dropperful equals 2000 milligrams of acetaminophn 

Return to Lesson Plans


   1 | 2 | 3