1.21 write word equations and balanced chemical equations to represent the reactions studied in this specification

Writing balanced chemical equations

There has to be the same number of each atoms/element on both sides of the equation.

Aluminum + copper (II) oxide----> Aluminum oxide + copper

      Al       + CuO           ---->          Al₂O₃   + Cu

1 Al                                            2Al
2 Cu                                           1Cu
1 O                                             3 O


There needs to be the same amount of each elements on both sides, so we must balance it.

2Al + 3CuO ----> Al₂O₃ + 3Cu

2 Al                    2Al
3Cu                    3Cu
3 O                     3O

Now the equation is balanced.