Year 8 · Science · Chemical reactions · Lesson 3
Oxidation and thermal decomposition
Oxidation of metals, rusting and how to prevent it, and the thermal decomposition of metal carbonates, with mass calculations.
25-minute video lesson
Teaching, worked examples and 20 practice questions solved step by step.
Watch free for a monthWhat your child will learn
- Describe oxidation
- Write word equations for metals reacting with oxygen
- Explain what iron needs to rust and how to prevent it
- Write word equations for the thermal decomposition of carbonates
- Calculate the mass of gas given off
The method
- Oxidation is gaining oxygen: metal + oxygen → metal oxide.
- Rusting: iron + oxygen + water → hydrated iron oxide; it needs both air and water.
- Thermal decomposition breaks a substance down with heat: metal carbonate → metal oxide + carbon dioxide.
- The mass of gas given off = mass before − mass after.
Key words: oxidation, metal oxide, corrosion, rusting, galvanising, thermal decomposition, carbonate.
Worked examples
The first three practice questions from the lesson, with every step.
Question 1
Write the word equation for zinc reacting with oxygen.
- Step 1: zinc + oxygen
- Step 2: → zinc oxide
Answer: zinc + oxygen → zinc oxide
Question 2
Write the word equation for iron reacting with oxygen.
- Step 1: iron + oxygen
- Step 2: → iron oxide
Answer: iron + oxygen → iron oxide
Question 3
Write the word equation for calcium reacting with oxygen.
- Step 1: calcium + oxygen
- Step 2: → calcium oxide
Answer: calcium + oxygen → calcium oxide