Cloud in a Bottle Lab

Cloud in a Bottle

This experiment
illustrates the effect of pressure change and aerosols on cloud formation. 

Materials: 

1)  Two clear, empty, plastic water bottles with
lids.  Remove labels. 

 

2) 
Matches. 

Directions: 

· 
For
the first bottle, add about 1 inch of hot tap water and put the lid
on.  Shake vigorously.

· 
Look
through the bottle.  It is best viewed in
good lighting against a dark background.

· 
Squeeze
the bottle as hard as you can, then release it. 
Repeat this 5 or 6 times.

· 
You
are trying to see if there is any change in the air inside the bottle.  To get a clear view, swirl the water around
to remove condensation from the inside walls of the bottle.   

· 
For
the second bottle, again add about 1 inch of hot tap water, put the lid on, and
shake.

· 
Take
the lid off, light a match, blow it out, drop it into the bottle while it is
still smoking, then immediately put the lid back on the bottle.

· 
Again
look through the bottle, squeeze the bottle as hard as you can, then release
it.  Repeat this several times.  Swirl the water as needed to remove
condensation from the inside walls of the bottle.

· 
Safety
precautions are always important “in the lab”.  Take a moment to put the matches away, out of
reach of children.  Thanks!

Which bottle had better cloud
formation, the one with smoke in it, or the one without? 

Did the cloud appear when you caused high pressure on the air in the bottle (by
squeezing), or when you caused low pressure (by releasing)?

What is happening?

The warm moist air in the
bottle is close to saturation.  Squeezing
the bottle increases the air pressure which also causes an adiabatic
temperature increase.  This increased
temperature allows more water to evaporate. 
Releasing the bottle decreases the pressure and temperature slightly and
causes the excess water vapor to condense. 
The smoke particles are condensation nuclei which improve cloud
formation. 

The formation of the cloud
when the pressure decreases is analagous to what happens to a parcel of air
rising in the atmosphere.

Answer the following questions,
based on the experiment and these sections in your textbook:  Dew-Point Temperature, page 495
Adiabatic Temperature Changes, page 498
Condensation and Cloud Formation, page 596

The amount of vapor needed for
saturation ________ with increasing temperature.

  increases
  decreases

Saturation occurs if  sufficient water
vapor is added to air, or if air is cooled to its dew point.

  True 
  False

Cooling below the ________ causes
water vapor to condense.

Air that is allowed to expand
________;  air that is compressed
________. 

  cools;
warms
  warms; cools

When a parcel of air moves upward,
it expands and cools.

  True
  False

In order for a cloud to form, air
must be cooled below its  _____
 point.

In the experiment, squeezing the
bottle causes pressure and temperature to ________; releasing the bottle causes
pressure and temperature to _________.

  increase;
decrease
  decrease; increase

Tiny bits of particulate matter
known as ________ serve as surfaces for water vapor condensation.

Give two examples of condensation nuclei. 

Explain why the cloud appeared when
you released the bottle.