What causes dew to form drops on plants, water to bead on a waxed car, and bubbles to accumulate in soapy water? The answer is surface tension. Learn more about surface tension with a pan of water, some dishwashing liquid, and a paper fish.
Useful Vocabulary
Molecule: The smallest unit of a compound. For example, a water molecule is the smallest unit of water.
Intermolecular forces: The forces of attraction (coming together) or repulsion (moving apart) that occur between a molecule and its neighbors.
Cohesive forces: The forces of attraction that encourage molecules of the same type to stick together.
Surface tension: The strong intermolecular attractive and cohesive forces between molecules of a liquid at the surface. Surface tension helps liquid stay together, as it does when water beads on glass or smooth surfaces.
Materials
To do this activity you will need:
Roasting pan filled halfway with cold water (1)
Paper fish (1)
Medicine dropper filled with dishwashing liquid (1)
Directions
Gently place the paper fish on the surface of the water at one side of the roasting pan. The fish shouldn't move from that spot.
Place a drop of dishwashing liquid in the hole in the middle of the fish. What does the dishwashing liquid do to the surface tension of the water? What effect does this have on the paper fish?
Downloads and Links
Investigating Surface Tension with Paper Fish Student Guide
PDF
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