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The Density of Water
Matter occupies space and therefore possesses volume
and mass. The relationship between a specific amount of matter and the
volume it occupies is expressed as density. Density, then, is the relationship
between the mass and volume of a substance.
The unit of density is expressed as mass in grams per
milliliter (g/ml). Water is unique in the way its density changes with
temperature. Continued cooling of water will increase density to a certain
point, but then water does something quite odd compared to other liquids.
It becomes less dense between 4°C and when it becomes ice!
Thermometer
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Hydrometer |
Ice (or a freezer) |
- Using a hydrometer, measure the density of a tap water sample.
Measure the tap water's temperature and record both.
- Use ice (or a freezer) to chill the water sample. As the water
is chilled, select at least three other temperatures between the
initial tap water temperature and 4°C. Record density for
these three points.
- Continue to chill the water until a temperature of 4°C is
reached. Measure the density at 4°C and record it.
- Continue to chill the sample and record both temperature and
density
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| *As an extended exercise, try measuring
and comparing the densities of fresh and salt water. |
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