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CLOUD CHAMBER OBSERVATION LAB

In the video "STRANGE CASE OF THE COSMIC RAYS" you learned how an invention called a "CLOUD CHAMBER" changed science research on the structure of atoms. According to the video, a cloud chamber lets us observe the footprints of henchmen created by cosmic particles from outer space.

The footprints that we observe in the cloud chamber are actually vapor trails which pass through clouds of cold alcohol vapor.

The henchmen that cause the vapor trails are electrons, protons, and atoms stripped of electrons which fly apart at high speed when cosmic particles collide with air atoms.

In the video, you learned that all of us are constantly bombarded by cosmic particles which pass right through our bodies! Some of the sub-atomic particles that pass through us have come from outer space (cosmic rays). However, we are also bombarded by particles from atoms that split up during natural atomic reactions right inside the Earth. There is a lot of empty space between the atoms in our bodies. Most of the time, particles pass right through us without colliding with an atom.

When a high-speed particle slams into an atom, things go flying! Sometimes, electrons go flying! Sometimes, a proton or neutron flies out of the nucleus. We call the new particle a secondary particle. Other times, the nucleus splits into two totally different elements. We call that reaction nuclear fission! The vapor trails from nuclear fission are very spectacular!

LAB EQUIPMENT REQUIRED:

Cloud chamber
Dry ice
Alcohol
Extra-bright flashlight
Standard laboratory report form

Before you actually set up the lab equipment, you need to draw the cloud chamber in the space on the back of this lab sheet.

Study the actual cloud chamber when you make your drawing. The cloud chambers we are using in our lab are slightly different from the cloud chambers in the video. Make sure your drawing shows an internal view of the cloud chamber. Your drawing must show the metal jar lid, the black absorbent material in the bottom of the lid, and the dry ice inside the ice bucket.

It is also important for your drawing to show the soft gasket under the acrylic plastic viewing window at the top of the cloud chamber. Without that gasket, the alcohol vapor would not form a cloud.
Draw and label the cloud chamber in the space below:

PROCEDURES FOR CLOUD CHAMBER OBSERVATION

EQUIPMENT SETUP:
1. Make sure that the jar lid is TOUCHING the piece of dry ice under it.
(Dry ice evaporates. You may need a new piece of dry ice to make the
cloud chamber work. The key instruction here is that the dry ice
MUST be touching the metal lid to keep the alcohol vapor cold enough.)

2. Carefully pour enough denatured alcohol on the two pieces of black paper so both pieces of paper are soaking wet. DO NOT have a pool of alcohol inside the jar lid! The alcohol WILL NOT form a cloud if the round piece of black paper is submerged in liquid.

3. Make sure that the sheet of clear plastic has formed a seal with the rubber
gasket on top of the plastic jar. (You might need to add more petroleum
jelly to the gasket to get a good enough seal.)

4. Wait a couple of minutes for the cloud chamber to get really cold. Then
shine the high-powered flashlight through the side of the cloud chamber.
It will be easiest to see the vapor trails from directly behind the flashlight.

Draw diagrams of particle vapor trails you observe in the cloud chamber. Draw your first diagram in the space below. Draw at least two more vapor trail diagrams on the back of this sheet. Write a short description of each drawing. Explain what made that particular vapor trail different than other vapor trails which you have observed. Remember, vapor trails are three dimensional; but your drawings are two dimensional! Your descriptions should describe differences in vapor trail velocity, thickness, straightness in three dimensions and whether collisions with other particles had occurred.