Science Activity
#9 - The Breathalyzer Test
All experiments must be done in the presence of a parent or teacher.
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Ideas
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Key Words
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Materials
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Procedure
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Observations
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Summary
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Questions
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WWW Links

Ideas to be Developed

Alcoholic beverages include wines and beers. Wines are most commonly fermented from the sugars in grapes. The alcohol in these beverages is a chemical called ethyl alcohol, or ethanol. The physical affects of drinking alcohol range from loss of coordination, vision, balance, and speech. These affects usually wear off in a matter of hours after a person stops drinking. Because of alcohol's effects on the body and on behavior, governments often regulate its use to prevent accidents on the road.

Every year in B.C.

  • 200 people are killed in drinking driving accidents
  • 6000 people are injured by drinking drivers

It is a criminal offense if you drive with a Blood Alcohol Concentration (BAC) in Excess of .08%

What does it mean and how do law enforcement officers measure blood alcohol level concentration?

Law enforcement officers use portable breath-testing machines to find out whether a driver has a blood alcohol level above the legal limit. A breathalyzer is a device that samples the breath of a suspect and uses a chemical reaction involving alcohol that produces a colour change.

Inside the breathalyzer are chemicals with different colours. Potassium dichromate, K2Cr2O7, is a yellow-orange compound. When alcohol vapor makes contact with the yellow-coated crystals, the color changes from yellow to green.The degree of the color change is directly related to the level of alcohol in the suspect's breath.

Measurements taken with the Breathalyzer are reported in units of percent blood-alcohol concentration (BAC). In B.C., a BAC of 0.08 % is sufficient for a DUI (Driving Under the Influence) or DWI (Driving While Impaired) conviction. A blood alcohol concentration of 0.08% is equal to

0.08 grams of alcohol per 100 mL of blood

 


Key Words
Breathalyzer - A portable breath-testing machines to find out whether a driver has a blood alcohol level above the legal limit.
Ethanol - The ingredient in alcoholic beverages.

Materials Required

Consult with parents to find out the alcohol content of some alcoholic substances. Bring
your finding to class for discussion.

Alcoholic Substances
Alcohol content
beer
 
white wine
 
red wine
 
cooking wine
 
brandy, vodka, whiskey
 

 


Procedure

DEMO with class participation

1. Set up the demonstration with two 50 mL beakers. One of the beakers will be the reference.
2.
Add 30 mL of water to each beaker. Dissolve a small amount of potassium dichromate, K2Cr2O7, in each beaker. Stir until the solid is dissolved.
3. To each beaker, add a few drops of sulfuric acid. This creates the acidic environment needed for the chemical reaction.
3. To one of the beakers, add alcohol. Watch what happens to the potassium dichromate when alcohol is present. Compare the colour observed in this beaker to the reference beaker.

Demonstrate this quantity:

  • 0.08 grams of alcohol per 100 mL of blood


Observations

Appearance of potassium dichromate, K2Cr2O7, in the absence of alcohol

 

 

 

 

Appearance of potassium dichromate, K2Cr2O7, in the presence of alcohol

 

 

 

 


Summary
 

Questions

1. List the alcoholic substances in order increasing alcohol content.





2. Explain how the breathalyzer works to an adult.



Adult signature:____________________


WWW Links
Commercially available alcohol level tester
How Breathalyzers Work

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Ideas
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Key Words
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Materials
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Procedure
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Observations
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Summary
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Questions
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WWW Links

Howard Debeck Elementary School
8600 Ash Street Richmond, B.C. V6Y 1S2
Phone: 604-668-6281 - Fax: 604-668-6004


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