This section contains a range of experiments that you can try out in the comfort of your own kitchen or school classroom. They all use easy to get hold of items, but some can be a bit dangerous if you don't take care. Please get a responsible person to help if you're unsure and be careful with anything involving fire. Explanations to why the experiments work are included on all the pages but I haven't gone into detail about controls, variables and experimental plans. If you want to just have a bit of fun then you can use the experiments as they are. But if you are doing them at school or for a science fair project, you will need to have a read of the section below so that you think about things like controls and variables before you carry out the experiment.
Doing an experiment - The Scientific Method
The plan: Every experiment needs an aim - this is important because it tells us what we want to find out. For example, "Find out what happens to an old penny if I soak it in vinegar." After the aim comes the method. This is how we will be carrying out the experiment. Consider controls, what variables you want to vary, how many repeats you need, and how you are going to measure the results. The apparatus you require is also important - you can draw a diagram to show how everything should be arranged. Only when you've planned everything should an experiment be attempted!
Controls: When planning an experiment, try to think about what controls you should include. Controls are needed to make sure that it really is what you are testing that is causing the result. For example, a doctor testing a new drug on a patient needs a negative control - someone who hasn't received the drug - to ensure that the person given the drug isn't just getting better by themselves. In the coloured pennies experiment, a good negative control would be a penny that you have left as it was when you started. It means you have something to compare the pennies you've been testing with at the end of the experiment.
Variables: Can you work out what the variables are in your experiment? These are anything that you change in the experiment. To make an experiment really good, you need to vary just one thing at a time. Everything but the variable you are testing needs to be exactly the same for each experiment. For example, if we want to compare the effects of growing a plant in the light or in the dark, you would need two plants of roughly the same size - one kept in the dark and one in the light. You would need to make sure that the amount of water the plants receive, the temperature of the rooms, and every other variable you can think of is kept identical between the two plants so you can be sure that any difference really is caused by whether its been grown in the light or the dark.
Repeats: Repeating each experiment more than once makes us much more confident that any result we've seen is real and not just an accident. The more repeats you do, the more confident in your results you will be. Three is a good number of repeats.
Recording: Keeping really good notes is important for any experiment. If you finish the experiment and can't remember what it looked like to begin with, you won't really be able to say what changes have occurred. So write down exactly what you did at all stages, draw diagrams of experiments and the controls, makes tables of variables, and produce a report at the end so that someone else could repeat your experiment and get the same results. How are you measuring your results? Appearance, smell, size, speed? The changes that occur in your experiment are called the results and these should be written in your report after the aims, methods and apparatus diagram that you did at the start.
Conclusions: The conclusions are based on what happened during the experiment and what it has told us about our original aim. For example, if the aim was "Find out what happens to an old penny if I soak it in vinegar" and the penny changed colour while the negative control stayed exactly the same as it was at the start, we can conclude that vinegar changes the colour of a penny. The conclusions are the place to try and explain your results - to find out why vinegar changes the colour of a penny, you'll need to have a look at the coloured penny experiment on the right.