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Youth Council

SNWA

Select a science experiment:

Chemical
Concentrations

Soft or
Hard Water

Soft or Hard Water?
Tap water in homes may often be referred to as hard or soft depending on the amount of certain minerals it contains. The tap water here in Southern Nevada is usually found to be hard, since it contains large amounts of calcium and magnesium. Southern Nevada's water is safe to drink; these minerals are harmless, natural elements that can be found on a Periodic Chart of Chemical Elements.

You will need:
  • Pieces of chalk
  • Borax
  • Plastic bags
  • Teaspoons
  • Paper coffee filters
  • Soap powder
  • Masking tape
  • Hammer
  • Plastic container that pours easily
  • 3 Large clear jars with lids
  • Marking pen
Begin the Experiment
  1. Label one jar "H" for hard and another "S" for soft. Leave the third jar blank.
  2. Put the piece of chalk in the plastic bag and tie the opening. Use the hammer to break the chalk into small pieces.
  3. Open the bag. Use the hammer head or spoon to grind all of the chalk into fine powder.
  4. Fill the plastic container about two-thirds full with water. Add the powdered chalk to the water and stir well.
  5. Place the paper filter over the jar marked "H" and pour the chalk and water mixture through the filter into the jar. Pour until the jar is about half full.
  6. Repeat step #5, using the jar marked "S."
  7. To the jar marked "S," add two teaspoons of borax and stir
  8. Add a teaspoon of soap powder to each jar. Place the lids on the jars and close tightly. Shake each jar until suds form. (If no suds appear, add another teaspoon of soap powder to each.)
  9. Fill the remaining jar half full with tap water. Add a teaspoon of soap powder (add the same amount as you did to jars "H" and "S"). Close tightly and shake.
  10. Observe each jar closely and complete the following observations.
Observations
  1. What do you notice about the amount of suds produced in jar "H"?
  2. What do you notice about the amount of suds produced in jar "S"?
  3. How do jars "H" and "S" compare to the third jar with tap water?
  4. What can you conclude about the action of soap in hard and in soft water?
  5. Based upon your results in Step #9, what can you conclude about water coming out of this tap? Is it hard or soft?