| Factor | Likely influence on the dependent variable | Scientific Reasoning |
| The temperature | As the temperature increases the rate of reaction will increase | At low temperatures, enzymes work slowly. This is because the enzymes are only moving very slowly. Substrate molecules will not often collide with an active site and so binding between the substrate and the enzyme is a rare event (Jones, Fosbery and Taylor, 2001). As temperature rises, the molecules gain more kinetic energy and move around more. Collision happen more frequently and substrate molecules enter the active site more often. Collision happen with more energy and this makes it easier for bonds to be broken and the reaction to occur (Toole and Toole, 1991). Above a certain temperature the enzyme molecules begin to lose their shape: they become denatured and do not function correctly.The rate of reation will decrease. AT a certain temperature the the substrate will not fit at all or will not be held. The reation will not take place at all. I will ensure that in my experiment that the temperature is kept constant at 22oC |
| pH | Enzymes are specific in their optimal pH. | You would explain here how pH could influence your experiment |
You would need to discuss each variable that could influence the outcome of your experiment. You must state whether you are keeping the variable the same or not. Notice that references are quoted to support your work. You could also include small diagrams.
PREDICTION:This is where you stick your neck out and predict what you expect to find. eg "I predict that the density of lugworms will increase as the salinity of the sand increases". You then have to explain as fully as you can WHY you predict such a thing. Your explanation should be as scientific as possible, and should contain references to your text book. If you are testing more than one independent variable (eg he effect of salinity and particle size on lugworm density) you would write a prediction for each.
SAFETY: Include a secion in which you detail the risks involved in your experiment and how they were minimalised. You could quite information from Hazard Cards here if you are using chemicals.
PRELIMINARY WORK
Briefly detail any preliminary work you have done and what the results mean. Explain how the preliminary work has helped you design your method for this piece of course work- eg did it help you decide on a good range of concentrations? Did it help you choose a time period over which you could obtain relaible results for each replicate?
METHOD:Detail a step-by-step method for your experiment. It should be written in the future test as it is a plan! **Include an equipment list**
PRECISION and RELIABILITY.
To get the higher level marks you need to explain how your method will enable you to obtaion precise and reliable results.
PRECISION- is how close your measured value is to the actual value. You obtain precise results by measuring things using precise equipment- eg scales that measure to 2 decimal places, pippettes that measure to the nearest millilitre. How precise you need to be depends on the nature of what you are investigating. Do not exagerrate how accurate you have been.
RELIABLE- results are reliable when they are repeatable. Hopefully your preliminary work has given you information on a reliable approach- eg you know that a certain method produces results that are similar when you repeat it. You will be performing at least 3 (choose 4) replicates for each experiment. You will hopefully be assessing their reliability using statistics- a t-test or regression/correlation.