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OCR A Level Biology:復習筆記1.1.2 Identification of Variables

Category: A-level課程, 國際課程, 教材筆記, 福利干貨 Date: 2022年11月16日上午10:22

In an experiment, a variable is any factor that could change or be changed
There are different types of variables within an experiment
- The?independent variable: the only variable that should be changed throughout an experiment
- The?controlled/confounding variables: any other variables that may affect the results of the experiment that need to be controlled or monitored
- The?dependent variable: the variable that is measured to determine the outcome of an experiment (the results)
It is essential that any variable that may affect the outcome of an experiment is controlled in order for the results to be?valid
Preliminary research and preliminary studies can be used to identify variables within an experiment and to determine ways of controlling these variables effectively
The science surrounding the issue/problem being investigated is likely to contain information about different factors or variables that may exist

Enzyme rate experiments?are experiments that are carried out to determine the?effect?of?changing?a particular?factor?on the?rate of a reaction?that is catalysed by an enzyme
Factors that can be?changed?include:
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
The?key?thing with enzyme rate experiments is to ensure that?only one?of these variables is?changed?during a particular experiment
- This is known as the?independent?variable
All other variables must be?controlled?(they must stay the?same)
- These are known as the?control?variables
For example, if investigating the effect of?temperature?on the rate of reaction, the?pH,?enzyme?concentration?and?substrate?concentration?must be exactly the same (kept constant) each time you run the experiment (at each different temperature you are investigating)
If these control variables are not kept constant, they could?affect the results?of the experiment
- This would make the results?unreliable