Molecules are moving! What proof is there for this incredible statement, and what factors influence the kinetic energy of moving molecules? Demonstrate the motion of invisible ammonia and hydrochloric acid gas molecules by their colorful reactions with acid-base indicators. Then compare the rates of diffusion of different size molecules by reacting the two gases together in the ammonium chloride “ring test.” Finally, show the effect of temperature and use the teaching analogy provided with the kit instructions to illustrate the relationship between temperature and kinetic energy. Large, 18 mm x 30 cm glass demonstration tubes are a perfect size for viewing by all students. Enough materials are provided to perform the demonstration seven times.
Concepts: Diffusion, kinetic-molecular theory.
Time Required: 15 minutes
Materials Provided: Ammonium hydroxide, hydrochloric acid, phenolphthalein, thymol blue, Beral pipets, cotton balls, two glass diffusion tubes, medicine droppers, rubber stoppers.
Note: Perform this demonstration in a fume hood or well-ventilated lab.
Additional ResourcesNo Additional Resources at the time.
Flinn Catalog/Reference Manual Page 364
Flinn Middle School Catalog/Reference Manual Page 360
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