LaMotte HARDNESS IN WATER 1606 - Manual (Page 4)

WHAT IS WATER?
Water, a substance which covers approximately 75% of the Earth’s surface,
exists in three forms: solid, liquid and gas. In the solid form, ice, water is
used to cool drinks and other solutions, while the gas form, steam, can be
used to power turbines and engines. As a liquid, water is used in many
ways, from drinking to agriculture to providing homes for many kinds of
aquatic life.
Known as the universal solvent, “pure” water is able to combine with other
substances to form solutions. Even “natural” water found in the
environment contains dissolved gases, such as oxygen and carbon dioxide,
and dissolved minerals, such as iron and calcium. Although most of these
substances are not harmful at the levels commonly found, some substances
are toxic, or poisonous, to living things. Tests are available to determine
the levels of many toxic and nontoxic substances in water.
If dangerous or unhealthy substances are discovered, the water can be
treated to remove or destroy them. Some industries, such as agriculture, do
not need to treat water before using it, but others require water be purified
before use. For instance, many drinking water systems are treated with
chlorine to kill bacteria and disinfect the water, making it safe for
consumption. Other industrial processes add dangerous chemicals or
bacteria to the water, which must be removed or rendered harmless before
returning it to the environment.
Concern over the availability of usable water is increasing as the human
population increases. Polluted water will purify itself naturally over time,
but as more and more untreated, polluted water is returned to the
environment the system is overloaded and unable to work as well. Water
treatment processes, either chemical, biological or filtration, may be used to
supplement the natural purification process.
To determine the efficiency of treatment and levels of toxic and nontoxic
substances water must be frequently tested. When establishing a testing
program it is important to take samples over a period of time because the
character of the water constantly changes. By taking several samples,
determining their composition and keeping accurate records scientists are
better able to understand water.
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NOTES TO THE TEACHER
The materials in this kit are provided as tools to conduct several
experiments. In addition to the procedures described in this manual, a
number of open-ended experiments are suggested to spur the student’s
imagination to investigate related problems. Students can use the materials
in this and other test kits to develop additional experiments.
ADDITIONAL EXPERIMENTS
FOR HARDNESS IN WATER
1.
Obtain water samples from various natural water sources such as a
pond, stream or river. Test each sample for hardness and compare the
results.
2. Ask some students to bring in water samples from their homes. Test
the samples for hardness and compare results from municipally treated
water to untreated water.
3. Leave some containers out in the open to collect rain water. Test the
sample for hardness. How does rain water hardness compare to tap
water or water which was taken from a pond or a stream?
4. Add soil to one of the water samples before conducting a hardness
test. Mix thoroughly and filter. Test the filtered water for hardness.
What does the soil do to the hardness of the water sample?
5. Lime (calcium) is sometimes added to soil to adjust its pH. Add a
small amount of lime to a soil sample. In a funnel with filter paper
flood the soil sample with water and collect the water which percolates
through. Test the filtered water for hardness. What does lime do to
hardness of the filtered soil-water sample? How does this compare to
the sample in Experiment 4?
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