Combustion and Corrosion Reactions

Balanced chemical equation for the incomplete combustion of methane.

2CH4(g) + 3O2(g) -> 2CO(g) + 4H2O(g)

Balanced chemical equation for the combustion of magnesium

2Mg(s) + O2(g) -> 2MgO(s)

Endothermic Reaction

Absorb energy (get colder). The products have more energy than the reactants. To get going, the reactants absorb energy from their surroundings

What is a combustion reaction?

An exothermic oxidation reaction where something burns or explodes when it reacts with oxygen gas. O2 is always a reactant! eg. Mg + O2 MgO

Difference and Similairites combustion and corrosion?

Both are oxidation reactions, both involve a reaction between a metal and oxygen, but corrosion may also involve water.

Balanced chemical equation for the complete combustion of methane (CH4).

CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g)

What is a corrosion reaction?

Corrosion is the chemical reaction that breaks down metals (in the presence of oxygen) to form other compounds. OR Another type of oxidation reaction is corrosion. Most metals corrode when they are exposed to water, air, or other chemicals. The metals lose electrons when they are oxidised so they become a positive metal ion.

Exothermic Reaction

Exothermic reactions produce energy (get hotter or brighter). Reactants have more energy than the products.

What is the Law of Conservation of Mass?

Matter can neither be created nor destroyed. It follows therefore, that during a chemical reaction, atoms cannot be created or destroyed.

Reactants

Substances initially present in a chemical reaction that are consumed during the reaction to make products.

How do you know if there has been a chemical reaction?

chemical change- a new substance has formed: 1. Permanent Colour Change A colour change indicates that there has been a chemical reaction. Sometimes this can reverse, so to be sure it must be a permanent colour change. example: a car rusting 2. Gas Production Sometimes gas can be observed in the form of bubbles, but other times gas production is very difficult to detect. example: Soluble aspirin or Berocca tablets 3. Precipitate is made When two solutions are mixed and a SOLID (or a "precipitate") forms, a chemical change has occurred. 4. Metal Displacement When one metal coats another, a chemical reaction has occurred. The more reactive metal displaces the less reactive metal from the solution. 5. Temperature Change Some reactions absorb energy and others produce it (usually as heat). e.g endothermic e.g exothermic

How is rusting prevented?

preventing water and oxygen from getting to the metal eg. painting, putting oil on the metal, galvanising (coating with Zinc!!)

Signs of incomplete combustion?

soot, smoke, charcoal

Products

substances that are formed during the chemical change.