Writing Guide Home Design  


This should be the title or task that I have given you


You need to outline what you plan to carry out in this experiment

Research Question

You need to formulate a precise question about what you will do. This is going to be the focus of your investigation and must include the dependent and the independent variables.

“Is enzyme activity affected by concentration?” is vague and imprecise as it does not include independent or dependent variables.

“Does ethanol concentration affect the rate of oxygen production by bovine catalase?” is a good research question as it includes both the independent and dependent variables.

If your research question doesn’t have a question mark, chances are, it’s not a question! It is possible to do as an aim that’s not in the form of a question but it’s easier this way.


Although it is not strictly necessary for you to include a hypothesis, it is good practice as it will keep you focused. It will also give you something to refer back to when you are writing CE.

State what outcome you expect from carrying out the experiment and link it to the research question Example: “When x is increased y will ...”.

Explanation of Hypothesis

Whilst it is good to have a hypothesis, it is of little value if you can’t back it up with rational thought. This will most likely come from an external source so don’t forget to reference it.


A variable is a factor that is subject to change and there are four types of variables you need to consider:

● Independent variables
● Dependent variables
● Controlled variables
● Uncontrolled variables

Some of the most common variables are (this list is not exhaustive):

● Time
● Light intensity
● Surface Area
● pH
● Temperature
● Solution concentration
● Volume
● Materials used (this could be the source of the catalase used in an experiment)

Independent Variable

This is the variable that you are changing. Example: when you change the temperature to see the effect on yeast, temperature is the independent variable.

This is the x axis on your graph.

It is important that you chose a suitable range. If for example you expect 40˚C to be the optimum temperature, try and chose a suitable range either side of this so that you can get a good set of data.

It is also important to have a negative and positive control when applicable. Example: you are investigating the concentration of hydrogen peroxide on catalase, you would also do the experiment with distilled water as the negative control and an undiluted solution of hydrogen peroxide as a positive control. This will enable you to compare your other results. This is not always possible and if you can’t think of a way to include controls into your independent variable, leave it but you may be asked to do it if it is possible depending on what you are researching.

Dependent Variable

This is what you are measuring in the experiment.
Example: when you change the temperature to see the effect on yeast, the effect on yeast (such as the rate of reaction) is the dependent variable. If you are looking yeast catalase, the amount of O2 produced is the dependent variable.

This is the y axis on your graph.

Controlled Variable

Put simply, this is what you need to keep the same so that the results of the experiment are not affected.
Example: You are investigating the effect of substrate concentration on an enzyme so some of the variables you must keep constant are temperature and volume (there are others too) otherwise they would affect the results of the experiment and you wouldn’t know what change was due to substrate concentration changes and what wasn’t.

Uncontrolled variable

Some variables just can’t be controlled such as weather or the environment but you must make sure you minimise or monitor it.

In general though, you should always aim to control variables as best you can.
Example: background light through the window can be controlled using blinds and room temperature can be controlled using a hot water bath.

Don’t mention this section if you can’t think of any uncontrolled variables or you have controlled all the ones you can think of.

Presenting Variables

One of the easiest ways to present variables is by using a table. It ensures you do not miss out a variable and that you address the issue of how you control each one.

How the variables will be controlled
Dependent Variable
Details of the variable and how you are going to measure it
Independent Variable
Details of the variable and how you are going to change it
◦ Use bullet points if you are using different ways of to control it

Controlled Variables

Bullet point each variable you are going to control followed by

◦ How you will ensure they do not change during the experiment and prevent false results
◦ The examiner will clearly see how you intend to control them

Uncontrolled Variable
If this is not applicable, do not bother including it in the table

This table can end up being very large but this doesn’t matter as long as what is written is pertinent and of good quality.


● You should use bullet points for this
● Don’t use prose
● This is where you include all the materials you need
● This includes apparatus, chemicals and biological substances
● A person has to be able to do this experiment based on your instructions so the apparatus list must be accurate
● Don’t mention anything in your method that is not in the apparatus list
● Include quantities, volumes and concentrations
● After each piece of equipment, include the precision if known
● Examples are:
● 1x 5 cm3 ± 0.1 cm3 syringe
● 6x 250 cm3 ± 25 cm3 beakers
● 1x boiling tube (boiling tubes are a standard size as are test tubes)
● 500 cm3 3 % Amylase (as this will be provided for you, you are not expected to mention the uncertainty unless I give it to you unless or you make the solution yourself)
● 500 cm3 1mol dm-3 glucose solution Amylase (as this will be provided for you, you are not expected to mention the uncertainty unless I give it to you or you make the solution yourself)
● If you are asked to carry out an experiment you have planned and you haven’t asked for a specific material or piece of equipment you will not be allowed to have it


1. The method should show exactly how to do the experiment
2. I expect detailed descriptions of every step needed
3. This includes and should contain the information in the table you did on variables
4. How the dependent variable is measured
5. How the independent variable is changed
6. How the controlled variables are unchanged during the experiment
7. How you monitor uncontrolled variables
8. Your method is assessed on the likelihood that it will yield sufficient relevant data so you must make sure it is quantitative data that is collected and that you have enough measurements and repeats (minimum of 5)
9. The steps in the method should be numbered
10. This means you can refer to a specific point and say it has to be redone a number of times without having to repeat yourself
11. Use the SI Units when describing an apparatus. Example: “Collect the gas in a 25 cm3 measuring cylinder”
12. Do not fall into the trap of using words like “then” or “first”
13. Make each step very simple, think of it like instructions for a recipe
14. Avoid words like “and” in a step
15. A person should be able to do the experiment just by looking at the method and using the apparatus list
16. This may seem obvious but make sure your steps are in the right order, you’d be surprised how many people get this wrong.
17. Avoid imprecise terms like amount
18. You should say volume if you are measuring a volume or mass if you are measuring it by mass. Don’t say “Measure the same amount of glucose solution”.
19. Include in your method (at the end) how you are going to process and present the data
20. Be specific, I will expect you to say exactly what sort of processing you will do to the data and to specify what will be on each axis of the graph
21. Include any precautions you feel you should take in your method such as taking care hen pouring acid

If you are unsure about the clarity of your method, ask a family member or a friend who doesn’t do Biology. They’ll soon tell you if the method makes no sense.

After the method, provide a blank table for your results that is ready to be used

Draw a diagram of the experimental set-up. Try and draw it on the computer or scan it in if you can’t do it on the computer in case you have to resubmit you work. Otherwise, you would have to draw it again.

Temperature (°C)
Volume of oxygen produced per minute (cm3 min-1 ± x.xx cm3 min-1)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5

Risk assessment

Although you are not marked for this, it will always be useful to show that you are aware of any possible health and safety issues. This can include a mention of glassware, sharp objects or chemicals and precautions to take.