| To Demonstrate How Salt Content is Measured . . . |
| MATERIALS NEEDED: |
- Jar, 1 quart (1 liter)
- Measuring Spoon, Tablespoon (15ml)
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- Modeling Clay
- Cap from a Pen
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1. Fill the jar three-fourths full with water.
2. Put enough clay in the pen's cap so that it sinks when placed in the jar of water.
3. Add 1 tablespoon (15 ml) of salt to the water and stir.
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4. Observe any change in the position of the cap.
5. Continue to add 1 tablespoon (15 ml) of salt at a time until 5 tablespoons (75 ml) have been added.
6. Observe the position of the cap in the water after each tablespoon of salt has been added.
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RESULTS: The cap rises in the water as more salt is added.
WHY? The upward push of the water on the cap is called the buoyancy force. This force increases with the weight of the water. Fresh water (water without salt) is less dense than salty water. As the salt content of the water increases, the water becomes denser and has a greater buoyancy force, which lifts the cap higher in the water. The floating cap acts as a
hydrometer, an instrument used to determine the salt content of water.
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