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Observing
Air Stratification
Introduction
This
experiment works best in a room with a very high ceiling. It also
works best when there is a mixture of warm and cold air in the room.
This might occur late in the day during the summer, when there
is still hot air in the room but the air conditioner has been just
turned on to cool the air inside the room.
Objective
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To observe air stratification in our daily lives. |
Equipment
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Clamps
and stand |
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Datalogger
interface connected to a PC |
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2
temperature sensors |
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Metre stick |
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BluTack/tape
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Experiment
Setup
Set
one of the external temperature sensors hanging down 3-5cm above the
floor. Don't let it touch the floor, because the floor itself might
be warmer or cooler than the air right near the floor. Use BluTack
to hold it in place against the table, but make sure it does not touch
the wall either. There should be air all around the sensor.
Place the other temperature sensor about 2 metres from the floor, but
don't put it right above the computer monitor. The monitor gives off
heat, and this will affect the sensor readings. Use a bit of BluTack
to hold the sensor.
Connect the 2
temperature sensors to the datalogger interface. Place the interface in the middle of the 2 sensors. Use the datalogger
software to plot the temperature collected from the 2 sensors in the same graph against time.
Results and Answers
At first the two lines will be very close together. Give the sensor a
few minutes to register their new temperatures. Now look at the graph. Does the 2 lines show different temperatures?
If so, why do you think this is? And if not, why do you think this is?
Conclusion
"Air stratification" is the result of hot air rising and cold air sinking.
If you see a large difference, then you can see where all of your heat has gone! It is up near the ceiling, because warm air
is less dense and more buoyant than cold air, causing it to rise. Cold air is denser and less buoyant, so it settles down near
the floor. What if you do not see a difference? It could be that your ceiling is relatively low, so there is not enough room
for the air to stratify (split into warm and cold areas). It could also be because all of the air in the room is the same
temperature. Since it is the difference in temperature that causes stratification to occur, air that is the same temperature
does not stratify. Also, if there is noticeable air movement (like a draught or a fan) in the room, the air will be mixed
together and there will be less stratification.
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