This is a word equation for a chemical reaction:

Reactants

Products

Magnesium +

hydrochloric acid

Magnesium chloride

+ Hydrogen

Word equations

No atoms are created or destroyed in a chemical reaction.There should be the same number of atoms of each type of element on each side of the equation. Ie. # atoms in reactants = # atoms in products

Magnesium + Oxygen Magnesium oxide

Symbol equations

(s)

(l)

(g)

(aq)

E.g. H2

O2

CO2

H2O

C

State symbols

You can never change a formula when balancing an equation. You can only put number in front of a formula.Lets consider two molecules of CO2:

C2O XCO4 XC2O2X2CO2

Balancing equations

Word eqn: hydrogen + oxygen water

Skeleton eqn: H2 + O2

H2O

Atom count: 2 x H 2 x O 2 x H 1 x O

Balanced 2H2 + O2 2H2OChemical Equation

Making water

Symbol eqn: H2 + O2 H2O

Balance O: H2 + O2 2H2O

Atom count: 2xH 2xO 4xH

2xOBalance H: 2H2 + O2 2H2O

Atom count: 4xH 2xO 4xH

2xO

Making water

You try – balance these equations and add state symbols.

C + O2 CO2

H2 + O2 H2O

CH4 + O2 CO2 + H2O

Reversible reactions

The products of the reaction can react and make the reactants.Changes that can go backwards or forwards.Show with a double arrow:

Can you think of any reversible reactions?