Year 10 Science · Unit 2 · Lesson 9
Apply Worksheet
Learning Goals
Fill in the missing coefficients
Each equation below has one or more missing coefficients (shown as □). Write the correct coefficient in each box. Count atoms carefully, do NOT change any subscripts.
| # | Unbalanced equation (fill the boxes) | Atom check (fill in counts) |
|---|---|---|
| 1 | □ H₂ + O₂ → 2 H₂O | H: ___ = ___ O: ___ = ___ |
| 2 | 4 Fe + □ O₂ → 2 Fe₂O₃ | Fe: ___ = ___ O: ___ = ___ |
| 3 | CH₄ + □ O₂ → CO₂ + 2 H₂O | C: ___ = ___ H: ___ = ___ O: ___ = ___ |
| 4 | □ Na + □ Cl₂ → 2 NaCl | Na: ___ = ___ Cl: ___ = ___ |
Real-world context
Natural gas is used to heat homes and hot water systems across Australia. The main component of natural gas is methane (CH₄). When a gas boiler operates correctly with sufficient air supply, complete combustion occurs. However, if the boiler is poorly maintained or the flue is blocked, incomplete combustion can occur, producing carbon monoxide, the leading cause of non-fire-related fatal poisoning in Australian homes.
(a) Write and balance the equation for complete combustion of methane (CH₄). Include state symbols: CH₄ is a gas, O₂ is a gas, CO₂ is a gas, H₂O is a gas at combustion temperatures.
(b) Write and balance the equation for incomplete combustion of methane (CH₄) producing carbon monoxide (CO) and water only.
(c) Using both balanced equations, explain what a home-owner could look for to tell whether their gas boiler is undergoing complete or incomplete combustion.
1. A student counts 2 oxygen atoms on the left side and 3 on the right in an equation and decides to change O₂ to O₃. Why is this wrong? What should the student do instead?
Wrap Up
In one sentence, what was the main idea of this lesson?