Part A: Corrosion

  1. Corrosion is the slow chemical change that occurs when a metal reacts with oxygen from the air to form a new substance called an oxide.
  2. An oxide is formed when a metal reacts with oxygen.
  3. Rusting is the corrosion of iron. It occurs when iron reacts with oxygen to from iron oxide (rust). Rust easily flakes off metal, leaving another layer of metal underneath to be attacked by oxygen. Rust will slowly eat its way through metal.

Aluminum also corrodes – it reacts with oxygen to form aluminum oxide. Aluminum oxide is much different from rust – it is strong and does not flake off. Instead, it acts as a protective coating so that no further corrosion can occur.

  1. Some ways to protect a metal from corrosion:
  2. Paint the metal surface so oxygen can’t get to the metal
  3. Coat the metal surface with oil so oxygen can’t get to the metal.
  4. Coat the iron metal with a metal like zinc that corrodes faster than iron. Once the zinc has all corroded away, it is replaced.
  5. Use plastics instead of metals (they don’t corrode at all!)… used in car bumpers – how come?

Part B: Combustion

  1. Combustion is when a substance reacts rapidly with oxygen and releases energy in the form of heat and light.
  2. When fossil fuels burn:
  3. Hydrocarbons and oxygen are the reactants
  4. Carbon dioxide and water are the two main products.
  5. Other products, like carbon monoxide and carbon, are produced when conditions are not ideal. Sometimes, there isn’t enough oxygen or heat for a complete burn, and hydrocarbons are hardly ever pure.
  1. The fire triangle looks like this:
  1. Fuel
  2. Oxygen
  3. Heat
  4. Oxygen
  5. Heat
  1. You should never operate a BBQ inside a building, because poisonous products like carbon monoxide will build up if there is not enough ventilation.

Part C – Word Equations

A word equation is a short way of representing a chemical reaction. It tells you what is used up and what is produced.

  • Reactants (starting substances) are written on the LEFT
  • Products (resulting substances) are written on the RIGHT
  • Reactants and products are separated with an arrow which means “produces”. The arrow points to the products.
  • Plus signs (+) are used to separate reactants from each other, and products from each other.

Examples:

Combustion of fossil fuels:

Hydrocarbon + oxygen  carbon dioxide + water

Corrosion of iron:

Iron + oxygen  iron oxide

Part D: Graphic Organizer for Contrasting and Comparing

  • Contrast the differences between corrosion and combustion in the T-chart. For every point you make for corrosion, you should make a point for combustion to show how it’s different.
  • Compare the similarities in the box below the T-chart. Each point you make should be true for both corrosion and combustion.

Combustion / Corrosion
Hydrocarbon + oxygen  carbon dioxide + water
Fast reaction
Gives off heat and light / Iron + oxygen  iron oxide
Slow reaction
Does not give off heat or light
SIMILARITIES:
-Both reactions use oxygen (except when silver tarnishes with sulphur)
-Both reactions produce oxides (combustion makes carbon dioxide and corrosion of steel makes iron oxide)
-Both can be destructive
-Both are examples of chemical reactions
-Both are non-reversible