Identifying Control Variables
Types of Variables
- 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 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
Identifying Control Variables: An Example - Science Surrounding Ideal Gases
- There are several experiments that can be carried out to investigate the properties of ideal gases
- Factors that can be changed include:
- Temperature
- Pressure
- Volume
- Number of moles of gas
- The key point with ideal gas 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
- When investigating Charles’ law:
- The temperature is varied (independent variable)
- The volume is measured (dependent variable)
- The pressure and number of moles must be kept the same (control variables)
- When investigating Boyle’s law
- The pressure is varied (independent variable)
- The volume is measured (dependent variable)
- The temperature and number of moles must be kept the same (control variables)
- If these control variables are not kept constant, they could affect the results of the experiment
- This would make the results unreliable
