The document discusses key concepts in chemical reactions including: balanced chemical equations show the same number and type of atoms on both sides of the reaction arrow; the law of conservation of mass states the total mass of reactants equals the total mass of products; reactants are the starting chemicals and products are the chemicals formed; and catalysts such as heat can be added to speed up reactions without being used up in the reaction itself.

1. Chemical
Reactions

2. A balanced equation
Notice that both sides of the
arrow have the same
numbers of elements

3. Law of Conservation of Mass
in a chemical reaction, the total
mass of the reactants is the same
as the total mass of the products
Antoine Laurent Lavoisier
1743-1794

4. Law of Constant proportions
in chemical compounds, the ratio
of the elements is always the
same
Joseph Proust
1754-1826

5. Reactant
Reactants are any
chemicals that you
start with.
Reactants and Products
Product
Products are the
chemicals that are
made in the reaction.

6. In our example:
Hydrogen and Oxygen are the reactants
Water is the product

7. “While some reactions happen
spontaneously when reactants are
mixed, others will require a catalyst.

8. An example of a catalyst is the application of heat
to the reactants.
The catalyst is written over the top of
the arrow in the equation as drawn
below: