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INTRODUCTION
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| Students did
a research on the constituents of atmospheric air. Two students looked
into carbon dioxide and learned that there is a trace amount (less than
0.1%) of carbon dioxide in the air we breathe. The air we exhale
does not, however, have the same amount of carabon dioxide as atmospheric
air. |
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EXPERIMENT
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| limewater |
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syringe |
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limewater
with drinking
straw
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| Limewater
reacts with carbon dioxide. Carbon dioxide is the only constituent
of air that reacts with limewater. We have two beakers filled with
the same amount of limewater. In one beaker
we will inject atmospheric air with a syringe until it turns cloudy (colour
change is a sign that a reaction has occured). In the other beaker
with limewater we will blow exhaled air by using a straw. We will
keep blowing air until the limewater turns cloudy. |
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QUESTION
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| What do you
think will happen? |
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SOLUTION
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| The limewater
injected with atmospheric air took many, many, many injections before it
turned cloudy, but the limewater injected with exhaled air turned cloudy
very quickly. Exhaled air contains about 5% carbon dioxide.
Atmospheric air contains less than 0.1%; therefore, exhaled air has over
50 times more carbon dioxide than atmoshpheric air. |
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COMMENTS
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| The focus
of the experiment was to compare the amount of carbon dioxide in atmospheric
air with the amount in exhaled air. The students did not have to
prove that the only constituent in air that reacts with limewater is carbon
dioxide, nor were they expected to prove that the amount of carbon dioxide
in atmospheric air is a trace amount and in exhaled air about 5%. |
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| If students
wanted to be really innovative they could have brought in a bottle of soda
pop, made a hole in the cap, inserted a straw, immersed the other end of
the straw in limewater, then agitated the soft drink to release the dissolved
carbon dioxide into the limewater. By doing this they could determine
approximately how much carbon dioxide soda pop has compared to air. |
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