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Description: Allow students to visualize and understand ionizing radiation.
Disciplinary Core Ideas (DCI, NGSS):
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8, HS-PS4-2, HS-PS4-5
Time for Teacher Preparation:
30-60 minutes – To gather materials and set-up
30-60 Minutes (1 Class Period)
Science and Engineering Practices (NGSS):
Cross Cutting Concepts (NGSS):
Radioactive elements continually undergo a process of radioactive decay during which their nuclei emit high-speed particles and rays. These are much too small to be seen under a microscope. The Cloud Chamber was invented by an English physicist, C. T. R. Wilson, in 1911. It is an instrument designed for the study of the trails of radioactive emissions. The investigation is accomplished in the following way. First, the air must be saturated with water or alcohol vapor. When the high-energy particles flow through the air, electrons are knocked loose from some of the atoms and form ions. Ions act as excellent centers for condensation. This condensation, however, must be stimulated by cooling the air. The water vapor or alcohol condenses on the ions, leaving a vapor tail which clearly reveals the path of the ray.
Cloud chambers detect the paths taken by ionizing radiation. Much like the vapor trail of a jet airplane, the tracks in a cloud chamber mark where ionizing radiation has been traveling. The radiation itself is not visible. Radioactive materials are one source of ionizing radiation. Three types of rays are given off by a radioactive element. They are alpha particles (positive nuclei of helium atoms traveling at high speed), beta particles (high-speed, negative electrons), and gamma rays (electromagnetic waves similar to X-rays). Most of the tracks will be about one-half inch long and quite sharp. These are made by alpha radiation. Occasionally you will see some twisting, circling tracks that are so faint that they are difficult to see. These are caused by beta radiation.
Note: You can use radioisotope disks in each chamber in lieu of Coleman lantern mantle pieces. By providing Alpha, Beta, and Gamma sources , students will find that only the Alpha and Beta sources will produce tracks. This is because Gamma radiation is electromagnetic radiation not particles, and it’s the particles moving through the alcohol cloud that makes the tracks.
NGSS Guided Inquiry
Give the students radioactive samples and ask them to reduce/block the radiation to normal background levels with things they find in the classroom.
Explain about the different types of radiation and radioactivity. Tell students to design their own experiment, to detect different types of radiation, and then share their results with the class.
Observe the vapor trails produced within the cloud chamber and answer the questions provided by your teacher.
Note: You can radioisotope disks in each chamber in lieu of Coleman lantern mantle pieces. By providing Alpha, Beta, and Gamma sources , students will find that only the Alpha and Beta sources will produce tracks. This is because Gamma radiation is electromagnetic radiation not particles, and it’s the particles moving through the alcohol cloud that makes the tracks.
Post Discussion/Effective Teaching Strategies
Differentiated Learning/ Enrichment
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