Molecules can't be seen, but we can see the forces between molecules. Use this set of four demonstrations to show students what happens when molecules attract each other—or don't!
• Floating Oil Droplet The difference in densities of water and ethyl alcohol causes an oil droplet to “float” in the middle of a beaker.
• Bubble Shapes Straws and twist ties are used to create beautiful geometric bubbles when dipped in a soap solution.
• Capillary Action Measure and compare the ability of water and ethyl alcohol to rise in a glass capillary tube.
• Vanishing Volume What happens to the 5 mL that was lost when 50 mL portions of water and ethyl alcohol are added together?
Use each demonstration separately to illustrate different types of intermolecular forces, or perform them all together for review or assessment. Includes detailed Teacher Demonstration Notes, a reproducible student worksheet, real sample data, and answer key. Enough materials are included to perform each demonstration seven times.
Concepts: Surface tension, hydrogen bonding, dipole-dipole attractions, cohesive and adhesive forces, London dispersion forces.
Time Required: 30 minutes
Materials Provided: Isopropyl alcohol, ethyl alcohol, dishwashing detergent, glycerin, stirrers, twist ties, disposable pipets, capillary tube, and disposable Petri dishes.
Additional ResourcesNo Additional Resources at the time.
Flinn Catalog/Reference Manual Page 383
Flinn Middle School Catalog/Reference Manual Page 349
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