Materials and Their Reactions With Oxygen
(Oxidation Explained Simply)
1. What Are Materials?
Materials are the substances around us — metals, non-metals, fuels, food, wood, plastic, fabrics, etc.
Different materials react with oxygen in different ways.
2. What Does “Reacting With Oxygen” Mean?
When a material combines with oxygen from the air, a chemical reaction happens.
This process is called oxidation.
3. Why Do Materials React With Oxygen?
Because oxygen is highly reactive and tries to combine with other substances to form more stable compounds.
4. Types of Reactions With Oxygen (In Order)
Step 1: Burning (Combustion)
Materials: wood, paper, petrol, kerosene, LPG, coal
Reaction: material + oxygen → heat + light + smoke + ash + gases
It is fast and exothermic (releases a lot of heat).
Flame appears because gases are glowing when they get hot.
Products of burning:
Smoke (tiny carbon particles + hot gases)
Gases (mostly carbon dioxide, water vapour, sometimes carbon monoxide)
Ash (the non-burnable part left behind)
Step 2: Rusting (Slow Reaction of Metals)
Mainly iron reacts with oxygen + water.
iron + oxygen + water → iron oxide (rust)
Very slow reaction.
Needs moist air.
Rust weakens metal.
Step 3: Tarnishing (Surface Reaction of Metals)
Silver reacts with oxygen + sulfur to form a black coating.
Copper reacts with oxygen to form greenish copper carbonate.
These are slow, happen on the surface only, not a full burn.
Step 4: Respiration (In Living Organisms)
Glucose in food reacts with oxygen.
Glucose + oxygen → carbon dioxide + water + energy
Slow and controlled.
Also exothermic but not explosive.
Step 5: Decay (Rotting of Food/Wood)
Microorganisms use oxygen to break down materials.
Produces gases and smell.
Slow reaction.
5. Types of Chemical Reactions Involved
A. Exothermic Reactions (Give Out Heat)
Examples:
Burning wood
Burning fuels
Respiration
Rusting (very slow heat release)
Why exothermic?Because new bonds formed with oxygen release energy.
B. Endothermic Reactions (Take In Heat)
These reactions absorb heat instead of releasing it.
Examples related to oxygen:
Some metals (like mercury oxide) break down into oxygen only when heated.
Photosynthesis is endothermic:carbon dioxide + water → glucose + oxygen(plants absorb sunlight)
6. Summary in Steps (Easy to Memorize)
Materials + oxygen = oxidation.
Fast oxidation = burning → heat, light, smoke, gases, ash.
Slow oxidation = rusting, tarnishing, decay.
Living organisms use oxygen for respiration → energy.
Most oxidation is exothermic.
Some reactions absorbing heat → endothermic.