Parts per Million Lab
Name______Date______Pd______
Topics Covered: parts per million (ppm) parts per billion (ppb) serial dilution, Tyndall Effect
Background:
In this activity you will investigate the concept of parts per million (ppm), a unit of measurement. People are often concerned with materials in very small quantities or concentrations. Sometimes when discussing water or air scientists will have to talk about what is in the fluid in terms of parts per million(ppm) or parts per billion(ppb) because the amounts are so small. A concentration of 1 ppm corresponds to 1 part material per 1 million parts of a gas, liquid or solid medium it is found in. But just because these amounts are small does not mean that they are unimportant. For example, fish like bass require a dissolved oxygen level of at least 4 ppm. The ambient (normal) air quality standard for the pollutant sulfur dioxide (SO2) is 30 ppb.
Living things can be affected by very small amount of a material in water. It is important to know the human tolerance level of a substance. As technology develops, people are able to use more sensitive equipment and test techniques to detect tiny concentrations of pollutants or contaminants in our drinking water supplies. The smallest amount that can be detected is the detection limit. The smaller the detection limit, the more we know about what is in our drinking water, and the more can be done to keep our supplies safe.
As an example, Fort Detrick here in Frederick County uses blue gills, a type of pollutant sensitive fish, as a monitoring system to ensure the bases drinking water is safe from contaminants. Today scientists are able to detect some materials at parts per billion or even parts per trillion concentrations. Do you think you cold detect a tiny amount as one part per million?
Materials:
7 clear plastic cups flashlight
dark colored unsweetened drink light/dark paper for background
milk 10mL and 100 mL graduated cylinder
plastic spoon marking pencil (wax pen)
Procedure: Steps to follow to complete the experiment follow closely to avoid errors
1. Precisely measure 100 mL of water and add the contents of one drink mix packet of kool aid into a clear plastic cup. This concentration will be called 1/1, one part per one.
2. Label the cups 1-7 with # 1 being the cup with the drink mix
3. Precisely measure 90 mL of water in to each of the other six clear plastic cups.
4. Precisely measure 10 mL of the liquid from cup #1 and stir it in to cup #2. This concentration is 1/10 this is one part per ten
5. Precisely measure 10 mL of the liquid from cup #2 and stir it in to cup #3. This concentration is 1/100 this is one part per hundered
6. Precisely measure 10 mL of the liquid from cup #3 and stir it in to cup #4. This concentration is 1/1000 this is one part per thousand
7. Precisely measure 10 mL of the liquid from cup #4 and stir it in to cup #5. This concentration is 1/10,000 this is one part per ten thousand
8. Precisely measure 10 mL of the liquid from cup #5 and stir it in to cup #6. This concentration is 1/100,000 this is one part per hundered thousand
9. Precisely measure 10 mL of the liquid from cup #6 and stir it in to cup #7. This concentration is 1/1,000,000 this is one part per million
10. Rinse the container and repeat the experiment using milk as the liquid in cup#1. ( Add 100mL of milkl\ to cup#1. Fill the other cups 2-7 with 90 mL of water, and then proceed with the dilutions.
11. Check each container for the Tyndall effect. The Tyndall effect allows you to detect the presence of a material when suspended in a fluid. Check for the Tyndall effect by shining the flashlight into the liquid from the side. If you can see the light beam passing through the liquid, then you know something else is in there.
Cup # / Concentration / Concentration / Color with Drink mix / Color with Milk / Tyndall EffectYes or No
#1 / 1/1 / 1 part per 1
#2
#3
#4
#5
#6
#7
Tyndall Effect:
The particles of a suspension will cause a beam of light to scatter as it passes through the suspension due to the reflection of light off the large particles. Since the particles are randomly arranged within the suspension, the reflection of the light is randomized, which causes the light to scatter. This scattering of light is clearly visible to an observer. Since the particles of a solution are much smaller, there is no discernible reflection of light. Therefore, it is not possible to see a light beam as it passes through a solution.
Whenever a driver encounters a foggy area on a highway at night, the Tyndall Effect is most evident. It is not possible to see distant beams of light coming out of a cars headlight as the car travels down the road. The atmosphere is a solution of gases. Bt when a car drives through fogbank, the lights beam are easily see. Fog is a suspension of water molecules in the air. In fact, the driver must be sure that the car’s lights are on “low beams” because there is so much scattering of light. If “high beams” are on, the reflection of light against the suspended water droplets can impair the vision of oncoming drivers.
Gases in the Atmosphere Concentrations
Gas / As a common fraction / As a decimal fraction / As aPercent / ppm / ppb
Nitrogen / 78/100 / 0.78 / 78.0 / 780,000 / 780,000,000
Oxygen / 19.0
Argon / 0.93
Neon / 0.0018
Helium / 0.00052
Krypton / 0.0001
Hydrogen / 0.00005
Xenon / 0.000008
Ozone
(Ground Level) / 0.000001
Ozone
(Stratospheric level) / 0.001
Questions for further analysis:
1. At what concentration did you notice that the color of the drink mix was no longer visible?
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2. At what concentration did you notice that the evidence of the milk was no longer visible?
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3. How do you think a concentration of 1 part per million of salt water would taste? ( DO you think you would be able to detect the salt in the water)? Explain.
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4. If you cannot see a diluted chemical in drinking water,does that mean that the water is safe to drink? Explain
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5. Calculate how many parts per million of salt are found in a 3.5% salt solution?
(note: 1mg/L = 1ppm, 1mg= .001 gram of salt ______
6. If you were the toxic manager of a factory, you might be responsible for diluting dangerous chemicals to safe levels in order to dispose of them legally and safely. If one liter of a sample of a chemical waste had a concentration of 5000 ppm, how much water would have to be added to dilute the sample to an acceptable level of 5ppm? Show your calculations!!!
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