Group 1/2 flame colors and water hardness treatment
ChemistryInorganic ChemistryAges 17–18Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Inorganic Chemistry
Flame test mode: hold a salt sample of Li, Na, K, Ca, Sr or Ba in the burner flame, watch the flame turn the characteristic color, and see the emission line appear at the right wavelength on the spectrum band. Water hardness mode: a beaker of water contains Ca²⁺, Mg²⁺ ions with HCO₃⁻ or SO₄²⁻; choose a softening method (boiling, Na₂CO₃, just enough Ca(OH)₂, ion exchange) and press Run to watch the precipitate form, the ion count drop, and the hardness recalculated in mmol/L. The lather mode: shake the same amount of soap or synthetic detergent with distilled, soft and hard water (Ca²⁺, Mg²⁺) and a treated sample, measure the foam height, see the white scum of calcium stearate, count the drops needed for a lasting lather and work out the hardness.
Lesson: Group 1 and Group 2 metals: characteristic flame colors; temporary and permanent water hardness and softening methods
What it shows
Two related topics on Group 1 and Group 2 metals. In a flame test, heat excites electrons in the metal ions to higher energy levels; when they fall back they emit light of fixed wavelengths, so each element gives its own flame color and emission line. Water hardness comes from dissolved Ca²⁺ and Mg²⁺ ions. Temporary hardness involves hydrogencarbonate and is removed by boiling, which decomposes HCO₃⁻ and precipitates CaCO₃; permanent hardness from sulfates and chlorides needs carbonate precipitation or ion exchange. The lather test shakes soap or a synthetic detergent with distilled, soft and hard water: soap forms a white scum of calcium or magnesium stearate and lathers only after all the hardness ions have precipitated, so counting drops to a lasting lather measures hardness, while the detergent lathers in any water.
How to use
Choose Flame color or Water hardness at the top. In flame mode, pick a metal, press Run and compare the flame with the position of its line on the spectrum band. In water mode, set the Type of hard water, pick a Softening method, press Run and read the hardness bars in mmol/L and the soap result. Try Boiling on temporary, then permanent, hard water before testing Na₂CO₃ and Ion exchange. In Soap lather mode, pick the Cleaning agent and the Test, press Shake all 5 tubes and read the foam heights, or choose a tube and add drops until the lather lasts; then compare with the detergent.
Parameters you can change
- Content Flame color, Water hardness and softening, Soap lather test
- Metal for flame test Lithium, Sodium, Potassium, Calcium, Strontium, Barium
- Type of hard water Temporary — Ca(HCO₃)₂, Mg(HCO₃)₂, Permanent — CaSO₄, MgCl₂, Total — both types
- Softening method Untreated, Boiling, Na₂CO₃ solution, Just enough Ca(OH)₂, Ion exchange
- Cleaning agent (lather test) Soap (sodium stearate), Synthetic detergent
- Lather test Same amount, measure the foam height, Count drops to a lasting lather
- Drops of cleaning agent per tube 2–30 drops
Questions to explore
- Why does Boiling soften temporary hard water but leave permanent hard water almost unchanged?
- Which metal gives a yellow flame, and why can it mask the flame colors of other metals?
- Which softening methods bring total hard water below 1 mmol/L, and how do they remove Ca²⁺?
Teaching ideas
All guides- Identifying Ions Virtual Lab: Flame and Precipitate TestsAn identifying ions virtual lab for the GCSE required practical: flame tests, sodium hydroxide, carbonate, halide and sulfate tests on unknown salts.
- Water Purification Virtual Lab: Analyze and Distill WaterA water purification virtual lab: measure pH and dissolved solids in tap, sea, rain and river water, then distill a sample and prove the distillate is pure.
