Arnold House School

Investigation

An investigation or experiment should have an aim.
What are you trying to find out?"
For example:

You must ensure an investigation is fair if you are trying to find the importance of one factor. Firstly you must identify the variables i.e. the conditions that if they were changed, might affect what you are trying to find out, e.g. water, oxygen, warmth, light, carbon dioxide, mineral salts
Only change one variable at a time. All the others should be kept as near the same as possible.
In an investigation where one variable is being changed to see its effect, this is called the experiment./li>
In most investigations you should also have a control, used for comparison; this should be set up as identical as possible to the experiment except for the variable being investigated; water/ oxygen/ warmth/ light/ carbon dioxide/ mineral salts. This you normally expect to work the best, because it has all the necessary conditions; (sometimes it is the one you expect not to work because it is missing one vital condition) e.g.Experiment – all conditions except Control – all necessary conditions.
If you are looking at the effect of several possible conditions (variables) in the same investigation, you can set up several experiments testing the various variables but just use the one control.

Never rely on one set of results because it may go wrong or may not do what is expected.
Set up more than one experiment, or combine class results, to give you an average result.
If necessary repeat the experiment, but remember it may be more difficult to keep the conditions (variables) exactly the same as before.
If investigating the effect of one type organism, use more than one e.g. use 10 seeds rather than one, 3 or 10 animals instead of 1

Sometimes you only need to observe to see which looks healthier or has grown the best.
Sometimes you need to count e.g. how many woodlice have chosen to go into the dark, how many animal/ plants there are in the sample / quadrat
Use the correct equipment. You may need to measure height/ length with ruler / tape measure, temperature with a thermometer, volume with a measuring cylinder, time with a stopwatch, pH with an acid/ alkali indicator, mass with a (top–pan) balance, force or weight with a newtonmeter

Remember to use your common sense but to work safely, e.g. wear safety goggles if there is a possibility of getting splashed in the eyes, be careful in case acids or alkalis are spilled, don't have 'naked' flames e.g. matches, bunsen burners, around alcohol that is flammable, wash your hands after handling chemicals or animals.

After leaving the experiment for a suitable length of time, e.g. minutes, hours, days, weeks, the results may be recorded in a simple table.You may decide the results are clearer as a bar chart, line graph or pie chart.
Look for any pattern; do the results change in a regular sort of way?
Look for any results that don't fit into the pattern i.e. experimental error and ignore these or repeat those results, to see if you have made a mistake.

The conclusion sums up the findings of an experiment.
It should relate to the original aim of the experiment.
Do not just describe your results.
In a graph, explain how as one thing altered, another thing changed. Rather than e.g. at the highest temperature the reaction was the faster,
Use an – er word e.g. the hotter the temperature, the faster the reaction,
Explain all parts of the graph e.g. at first the results increased then levelled off.
Quote some mathematical terms or figures e.g. directionally proportional, increased by the same amount each time, twice the time– twice the amount.