======Test for Hard Water======


<WRAP right box>
**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
\\
**Categories:** {{$demo.categories}}
\\


**Alternative titles:** 
</WRAP>

====Summary====                   
{{$demo.summary}}



====Procedure==== 
  -Add 100 mL of a water sample to a clean test tube; mark the water line (for reference).
  -Add 1.0 mL of a liquid soap solution (≈20 drops if no pipette); stopper.
  -Shake vigorously for 10 seconds; set down for 10 seconds; observe foam height and clarity of the liquid below.
  -Repeat the test with DI water (soft-water control) and additional sources (e.g., other taps) under identical volumes and timing.
  -Interpret: abundant, long-lasting foam with clear water indicates soft water; scant foam with cloudy/scummy water indicates hardness proportional to the soap volume required.




====Links==== 
To Test for Water Hardness, Soap Test - Simple Science and Maths: 
{{youtube>p6w6JAXAsRY?}}\\

Water Soap Test - Gordon Water Systems: 
{{youtube>tRyNjtlCiMI?}}\\

📄 Easy Ways to Test for Hard Water - Home Water 101: [[https://homewater101.com/easy-ways-test-hard-water]]\\


====Variations====
  *Prepare known mixtures of DI water and tap water (e.g., 25%, 50%, 75%) to create a semi-quantitative calibration of “soap volume to persistent foam.”
  *Compare soap vs a synthetic detergent to illustrate why detergents lather even in hard water.
  *Collect samples from hot vs cold taps and rank their relative hardness.



====Safety Precautions====
  *Wipe spills immediately—soapy floors are slippery.
  *Label all bottles; do not taste any samples.




====Questions to Consider====
  *Why must soap be used, not detergent? (Detergents lather in hard water; true soap reacts with Ca²⁺/Mg²⁺ to form insoluble scum, suppressing foam.)
  *Why does hard water turn cloudy on shaking? (Formation of insoluble calcium/magnesium soaps.)
  *How does the “soap volume to persistent foam” relate to hardness? (More soap required implies higher concentrations of Ca²⁺/Mg²⁺.)
  *Why run a DI water control? (To show the maximum foam response and check your shaking/timing method.)
  *How would boiling affect your results? (It can remove temporary hardness by precipitating carbonates, increasing foam in the boiled sample.)