• Chemical reactions involve collisions between molecules
– they are far too small
to see directly with the naked eye. Instead we make observations
which are evidence that a reaction has happened or is happening.
• For chemists, an observation
would be something that we can tell directly using our senses
, for example seeing a color change
, feeling a temperature change
(like a glass beaker warming up) or seeing gas being released
from a test tube.
• The reason this happens is because different chemical compounds have different properties that we can see when that chemical is produced
. For example a color change from brown to colorless might mean a reactant chemical that is brown is being converted into a product that is colorless.
• There are two ways to write that a reaction
is taking place:
a word equation
a chemical (symbol) equation.
• The → arrow found in a chemical equation is very important; it shows that a reaction is taking place. The reactants (what gets put in) of a reaction are always on the left-hand side of it, and the products (the new chemical that gets made) of a reaction are always on the right-hand side.
In this lesson, we will learn:
• How to determine
whether a chemical reaction has occurred.
• The methods
of writing a chemical reaction.