In the osmosis practical, often conducted with materials like potato slices and different concentrations of solutions, the independent variable is the factor that is deliberately changed by the experimenter.
Identifying the Independent Variable
Based on the reference provided, for the osmosis required practical, the independent variable is clearly defined:
Osmosis required practical variables: Independent variable: Concentration of sugar or salt solution.
Therefore, in a typical osmosis experiment investigating how concentration affects osmosis, you would change the amount of sugar or salt dissolved in the water to create solutions of varying concentrations.
Why is Concentration the Independent Variable?
- Definition: The independent variable is the one you manipulate or change on purpose to see how it affects another variable.
- In Osmosis Practical: When you set up tubes or beakers with different percentages of sugar or salt solution and place something like a potato piece (which contains water) in each, you are controlling and changing the concentration of the external solution.
- Observing the Effect: You then observe how this change in concentration affects the potato piece (e.g., its mass, length, or turgidity) due to osmosis.
Practical Considerations
As the reference notes, setting up and getting results from this practical within a standard lesson time can be challenging because:
- Preparing solutions of different concentrations takes time.
- The potato pieces need sufficient time immersed in the solutions for osmosis to occur significantly enough to measure a change. A short immersion time might yield negligible results.
- Analysis of results (weighing, calculating percentage change) also requires time.
To manage this, practicals might involve preparing solutions beforehand or leaving the experiment set up over a longer period.
Summary of Variables
Understanding the different types of variables helps clarify the experiment:
| Variable Type | Definition | Example in Osmosis Practical (Potato & Solution) |
|---|---|---|
| Independent | The variable that is changed or manipulated by the experimenter. | Concentration of the sugar or salt solution. |
| Dependent | The variable that is measured or observed as a result of the independent variable changing. | Change in mass or length of the potato piece. |
| Control | Variables that are kept the same to ensure a fair test. | Temperature, volume of solution, surface area of potato, type of potato, time left in solution. |
By systematically changing the concentration (independent variable) while keeping other factors constant (control variables), you can accurately measure its effect on the mass or size of the potato piece (dependent variable) due to osmosis.
