Excellent investigations

Keep it simple Change only one variable. Keep all the others the same. It’s not only easier to do only one experiment at a time, it’s also better science. Study only one factor, but do it right by doing duplicate or triplicate trials. Keep it simple Don’t be put off by what looks like simple chemistry or a simple question. There is plenty of scope to get excellence on every investigation.

If anything can go wrong, it will Get started early and be prepared for things to go wrong. Ideally, you need enough time to do the whole thing twice (when you discover you did it wrong the first time through). Expect to spend out-of-class-time in the lab. You’ll also need at least 4 days to complete your write- up.

Put everything in your log book Your log book should record everything to do with your experiment – in a form your teacher can read! If something is missing from your report but found in your log book, you may get marks for it. Likewise if there is no evidence in your log book of something that you claim to have done in your report, it may be discounted. Date every entry in your log book.

How do you know you’re right? Do it again! Every experiment should be done in at least duplicate. That means two bottles of orange juice left on the bench for a week, two buckets of water collected at each site, two packets of brand X and two of brand Y. If you only do it once, you can never be sure that your answer is typical or not.

How do you know your standard solutions haven’t changed over the three weeks of your experiment? Test them again! Maybe the concentration of your samples isn’t changing with time – maybe it is the standard that has changed. How can you be sure? Restandardise your solution at the end of the experiment.

Significant figures Your final result is only as accurate as your least accurate measurement. If you made up a solution using g of compound at some point, then your final result is only accurate to 2 significant figures. You cannot score Excellence on your project if you have mistakes in your use of significant figures. In the above example, greater accuracy could be maintained by accurately making up a more concentrated solution and then diluting it.

What’s the point? Your conclusion should answer your aim. Your research information should be related to your aim, and your discussion of what your results mean should also be related to your aim. If you find yourself unable to answer the question asked in the aim — change the aim!