CHM031 · Reactions & Equations · Classes 7–12
Balancing Chemical Equations
Objective: To balance chemical equations by counting atoms on both sides.
🧰 Virtual materials and apparatus
- Virtual atom balance
- Atom balls coloured by element
- Coefficient controls
📐 Formulas and SI units
atoms of each element: left = right
change coefficients, not subscripts
💡 Theory
Atoms are not created or destroyed in a chemical reaction, so a balanced equation has the same number of each kind of atom on both sides. We balance by changing the coefficients (the numbers in front), never the subscripts in a formula.
🪜 Guided virtual procedure
- Choose CH₄ + O₂ → CO₂ + H₂O.
- Count the atoms of each element on each pan.
- Change the coefficients until the beam is level.
- Read 'balanced ✓'.
- Balance the other four equations.
📋 Observations Simulated values
✅ Result and conclusion
CH₄ + 2O₂ → CO₂ + 2H₂O is balanced: 1 C, 4 H and 4 O on each side.
🔬 Real lab vs simulation
Balanced equations describe ratios of moles; real reactions may also need conditions such as heat or catalysts, written over the arrow.
⚠️ Safety
Equations only; the reactions themselves (burning, rusting) are not to be tried outside a teacher-led lab.
❓ Quick check
1. To balance an equation you change…
2. Balanced H₂ + O₂ → H₂O is…
3. Balancing shows conservation of…
🏋️ Practice
EasyBalance N₂ + H₂ → NH₃.
Answer: N₂ + 3H₂ → 2NH₃
MediumBalance Al + O₂ → Al₂O₃.
Answer: 4Al + 3O₂ → 2Al₂O₃
ChallengeAtoms of O in 2CO₂?
Answer: 4