you design an experiment you have to first 'set the scene'.
You are not ever
finding anything out without any preconceptions. You always have ideas
about what you are going to find out - you have expectations!
In a science experiement
these expectations will be based on:
- what you have
experienced in life,
you have carried out before and
knowledge (things you have been taught about science at school,
or have found out from books).
In your report you
need to explain to the reader what you expect to find out and why! You have to tell them your hypothesis.
You do not have
to look into a crystal ball and write down numeric predictions... just
predict a general trend. A good way to do this is to sketch a graph!
You do have to explain
the main scientific ideas that your prediction is based on. Try
to use scientific keywords in this section and explain in simple
terms what you understand them to mean.
A fair test situation
is vital for an investigation's results to be meaningful. You therefore
have to use the scientific knowledge you have explained to identify
the variables in your investigation - things you have to control,
otherwise it will not be a fair test. Say what will need to be controlled
and why - using theory to explain it.
One of the variables
will be the variable you are going to change. Say which on you
are going to change and by how much (the range over which you will change
it). Say how you found out that was a suitable range. It may well be
your preliminaries that helped you decide
on a suitable range! Then say have you are going to control all of the
others you have identified.
Your fair test must
be linked to your scientific knowledge.