CHM025 · Acids, Bases & pH · Classes 6–12
pH Scale Explorer
Objective: To explore the logarithmic pH scale and how it relates to hydrogen-ion concentration.
🧪 Simulation — virtual model
pHpH Scale Explorer
🧰 Virtual materials and apparatus
- Virtual 3D pH ruler with universal-indicator colours
- Beaker with H⁺ (red) and OH⁻ (blue) particles
📐 Formulas and SI units
pH = −log₁₀[H⁺]
pOH = 14 − pH (25 °C)
💡 Theory
pH = −log₁₀[H⁺]. Each step of one pH unit is a ten-fold change in [H⁺]. Below 7 a solution is acidic, 7 is neutral and above 7 is basic. In water at 25 °C, pH + pOH = 14.
🪜 Guided virtual procedure
- Set [H⁺] = 10⁻³ mol/L.
- Read the pH and see the beaker move along the ruler.
- Change [H⁺] by a factor of 10 and see pH change by 1.
- Go to pH 7 and above.
- Fill the table.
📋 Observations Simulated values
✅ Result and conclusion
[H⁺] = 10⁻³ mol/L gives pH 3 (acidic) and pOH 11.
🔬 Real lab vs simulation
Real pH depends on ion activity, not just concentration; pH meters are calibrated with buffers. Indicator colours are illustrative.
⚠️ Safety
Acids and bases are handled only by teachers; this activity is virtual.
❓ Quick check
1. pH of [H⁺] = 10⁻⁵?
2. pH 2 has how many times the [H⁺] of pH 4?
3. A pH of 9 is…
🏋️ Practice
EasypOH at pH 4?
Answer: 10
Medium[H⁺] at pH 7?
Answer: 10⁻⁷ mol/L
ChallengepH of 0.01 M HCl?
Answer: 2