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How Small is It?

Author: Brink Harrison


Time: One class period
Preparation Time: 5-10 min copying instructions for activities
Materials:

Instructions for activities:
How Many Sheets of Paper Activity
Measuring the Room Activity
How big is one drop?
Dilution Activity

Meter sticks
Rulers
One ream of paper
10 test tubes
Eyedroppers measured in ml or




Abstract
Students better understand what a concentration of one part per million means through activities

Purpose – By doing one of four possible activities the students will have a visual representation of a concentration of one part per million and will gain a better understand just how small an amount compared to the total amount this concentration means. They will be able to use this information when presenting their final report about the amount of arsenic present in the community.


Objectives

Students will be able to:-
1. Create a visual representation of what the concentration of one part per million means.

National Science Education Standards
Number and Operations
Understand numbers, ways of representing numbers, relationships among numbers, and number systems.
Representation
Create and use representations to organize, record, and communicate mathematical ideas.


Teacher Background
See attached sheets

Related and Resource Websites
http://www.awwa.org/Advocacy/learn/info/PartsPerMillion.cfm
http://www-ed.fnal.gov/trc/sciencelines_online/fall96/activities.html
http://www.ucar.edu/learn/1_5_2_24t.htm http://www.so.wustl.edu/science_outreach/curriculum/ozone/activities/1F-Measuring.pdf http://www.learner.org/jnorth/tm/PPM.html

 

 

Activity

Many people find water regulations and drinking water quality reports difficult to understand. Ask the students, “Have you ever heard about the “Maximum Contaminant Level” of a toxic in the water? What do you think it means?” (The MCL defines the maximum amount of contaminant that can be present in drinking water for the water to be considered safe.) Allow for guesses and discussion.

Tell the students, “Most often, the MCL is described as “X parts per million” or “Y parts per billion. For example, the MCL for Arsenic is or , according to the web site (In 2006 this MCL will change to 0.01ppm or 10ppb). http://www.dhs.ca.gov/ps/ddwem/chemicals/MCL/EPAandDHS.pdf

What does this mean? How small is one part per million? Allow time for examples and discussion. Tell the students, “Today we are going to do some activities that will give you a better picture of the size of one ppm and one ppb”.

Separate the class into groups and assign each of the groups one of the following activities.

I) Measuring the Room: Students find out how many cubic centimeter blocks are needed in the classroom to represent one part per million

The following activity is adapted from the activity described at the web site
http://www.so.wustl.edu/science_outreach/curriculum/ozone/activities/1F-Measuring.pdf.


1. Have the students in the group use meter sticks to find the length, width, and height of the room in centimeters, to the nearest whole centimeter

2. Calculate the volume of the room in cubic centimeters by multiplying these dimensions together.

3. To calculate how many cubic centimeter blocks are needed in the classroom to represent five parts per million in the classroom, use the formula:
                    

4. Have the students construct the appropriate number of cubic centimeter blocks to show the class what a concentration of 5 parts per million looks like.

5. Ask the group how they would represent 5 parts per billion.

II) How many sheets of paper: Students determine how many sheets of paper are needed to have one million if 1 represents the number 1.

The following activity is adapted from the activity described at the web site
http://www.learner.org/jnorth/tm/PPM.html


You will need a sheet of 8 1/2 x 11-inch computer paper and a pen or pencil.

1. Calculate how many square centimeters are in the sheet of paper

2. Mark off one square centimeter. Based on your calculation above, how many square centimeters would fit on one sheet of paper?

3. How many sheets of paper would you need to make your little square centimeter be one part per million?
4. A ream of paper is 500 sheets. How many reams would you need to represent 1,000,000 .5. How sheets of paper would you need to make one represent a concentration of one part per billion?

6. How many reams of paper would you need to represent a concentration of one part per billion?


III) How big is one drop? Students first determine the number of drops of water in one milliliter and use that number to determine how many gallons of water would equal 1 million drops?

The following activity is adapted from the activity described at the web site
http://www.learner.org/jnorth/tm/PPM.html


1. Take an eyedropper that is marked in milliliters and fill it with exactly 2 milliliters of water. Now squeeze the bulb slowly, drop by drop, counting exactly how many drops come out as you bring the level to 1 milliliter. How many did you count? Do 10 different trials of this.

2. Do you all get the same answer each time? If not, how far apart are the numbers? What might account for the differences? Calculate the average number of drops per milliliter.

3. Using the average number of drops per milliliter, calculate the number of milliliters would equal one million drops.
4. Convert into

5. That means one part per million is the same as one drop of a substance in a million drops, or Y liters, of water.

6. There are 3.78 liters in a gallon. Use this fact to calculate how many gallons are in Y liters. This will tell you that one part per million is also the same as one drop of a substance in about gallons.

7. If a bathtub holds about 60 gallons of water, how many drops of food coloring would be needed to bring a full bathtub to the concentration of one ppm?

8. How many gallons of water would you need if one drop of water were to represent a concentration of one part per billion?


IV) Dilution: Students will understand that a mixing ratio is the concentration of a certain substance expressed in parts per million or parts per billion by volume.

The following activity is the activity described at the web site
http://www.ucar.edu/learn/1_5_2_24t.htm

1. Using masking tape and markers, label the test tubes 1 through 10.

2. Put 9 ml of water in test tubes 2 through 10.

3. Put 10 ml colored liquid in test tube 1.

4. Take an eyedropper that is marked in milliliters and draw 1 ml of the colored liquid from test tube 1 into the eyedropper and transfer it to test tube 2.

5. Shake test tube 2 to mix the colored liquid and the water.

6. Draw 1 ml of the liquid in test tube 2 into the eyedropper and transfer it to test tube 3.

7. Shake test tube 3 to mix the colored liquid and the water.

8. Continue this process with the rest of the test tubes, 4-10. The concentration in each test tube is getting lower by a factor of ten each time.

9. Next fill out the mixing ratio in the chart provided. Test tube 1 contains pure color, so its mixing ratio is one part in one = 1/1 = 1. Write this down for the mixing ratio in the parts by volume column.

10. Test tube 2 has one part coloring for ten parts liquid. What is the mixing ratio? (1/10) Write this number in your chart and translate it into exponential notation ().

11. Continue this process for the other test tubes.

12. Now convert into parts per million by volume by multiplying the parts by volume (the second column). This will tell you how many parts per million by volume you have in each test tube.

Container number
Parts by volume
(mixing ratio)
Parts per million by
Volume (ppmv)

Parts per billion by
Volume (ppbv)

1

1/1 = 1

2

1/10 =
 
3
 
 
4
 
 
 
5
 
 
 
6
 
 
 
7
 
 
 
8
 
 
 
9
 
 
 
10
 
 
 

13. Convert the ppm into ppb by multiplying the number in column three by 1,000 (since one billion is 1000 times as large a one million)


Homework
1. If the students have not completed the calculations involved in their activities, have them do so for the first part of the homework. Tell them that they will present to the class tomorrow.

2. Have students come up with representations for one part per million given the following units to represent one unit:

a. one inch in how many miles? (5280 feet = 1 mile)

b. one cup in how many gallons? (16 cups = 1 gallon)

c. one pound compared to the weight of how many female adult blue whales?
(maximum weight of female blue whale according to http://www.acsonline.org/factpack/bluewhl.htm)

Embedded Assessment

Informal discussion about the meaning of ppm will allow you to assess how well the students understand the concept at the beginning of class. Informal observations and discussions about what they are doing in the activities will help you assess their ability to do the necessary calculations and assess how well they can visualize what a concentration of one ppm represents.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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Supported by NIEHS grant # ES06694


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