Planning (Know what you are going to do?)

Do some preliminary work to find out the best amount of chemicals to use, e.g. 22 mm of magnesium ribbon in 15 mL of 1M hydrochloric acid. This will help you to get some meaningful results, which are also repeatable.

Variable (the thing you change in the reaction, e.g. temperature of acid.) Make sure you only have ONE variable.

You need to mention fair tests, i.e. we kept the volume of water the same for each rusting experiment.

You need to mention safety. We chose a range (different numbers on the bottles) of acids from 0.2M to 2M to react with our marble chips. This was because if the acid was more concentrated the reaction was likely to fizz everywhere spilling a corrosive substance. Yes, do mention hazards on bottles and when you used goggles.

Never use abbreviations in your final account of the experiment. Don’t forget to include references to any textbooks you have used. This is standard procedure for chemists in research and industry! When writing up your coursework do it in the first person singular, i.e. I did the reaction 5 times to get a good average. Don’t say we, as although the examiner knows school chemistry department budgets are tight, it is supposed to be your work.

It is very helpful to include an apparatus drawing (2D not 3D) with an explanation. Say what the bits are and what they are called. If in doubt ask your teacher. When using diagrams from textbooks make them your own. Don’t just copy them out, e.g. draw the reaction in a conical flask, if the book shows it in a beaker.

Make a prediction. It’s not much of a chemistry experiment without one. A prediction is more than a guess. It is saying what you expect to happen based on some science knowledge, e.g. I predict that the reaction will be faster at a higher temperature because the chemicals will be moving faster and more reactants will collide with enough energy for the reaction to happen. The magic word is because. A prediction is even better when you put some numbers with it, i.e. you make it quantitative. Examples are when you predict time or rate (speed).

Obtaining (getting results) & Analysis (explaining them)

Good organization of the results is vital. Put results into well laid out tables with meaningful headings and units for the measurements. It’s often useful to have a column ready for the average readings as these are the ones that you will plot on a graph. You will need to take lots of readings and make sure that they are both reliable and repeatable.

Time (sec) Vol. H2 (g) cm3 Vol. H2 (g) cm3 Vol. H2 (g) cm3

0 0 0 0

10 14 15 15

20 25 24 25

30 29 31 30

Graphs are where lots of marks can be gained or lost. Bar graphs do have their place but in science it is in primary school. Make sure you do draw a line graph and the line of best fit. You don’t have to include all points, one or more points might not fit the pattern (anomalous) This line could be either a straight line or a curve! A detailed discussion of the results is need and this is where you must repeat the writing of the detailed science found in the plan. Link the science back to the prediction. Don’t worry if your prediction was incorrect. After all this is why scientists do experiments! High marks are awarded to students who read off values from their graphs or calculate several gradients.

Evaluation (what was it all about?)

Discuss only the original variable. Many students write lots about other variables. This is waffle that scores no marks. Remember it is quality not quantity! Discuss sources of error, i.e. things that affected the results and their reliability or repeatability. Discuss possible improvements in your experiment, i.e. I could have measured the volumes of liquids more accurately by using a pipette, burette or syringe instead of a 10 cm3 measuring cylinder. It is also useful to mention possible extensions to the method used, e.g. a video camera to allow you to work out the volume of gas more accurately every 10 seconds as you could use the freeze-frame facility. Mention the word anomalous. If your results are spot on then well done, you can always say the nearest thing i have to an anomalous result was after 90 seconds for the third set of results. You could also say ” i should have repeated the experiments at least six times to get a better average.”

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