Answer:
The independent variable is, different types of soil.
What you need to identify is a measurable dependent variable, which could be the rate of plant growth.
Now state your science project questions, such as:
How do different types of soil affect the growth of plants?
Independent variable: types of soil
Dependent variable: plant growth
Experiment:
Now you plan an experiment. Ask yourself question such as:
- How will you measure the plant growth? Changes in height is one idea. You could measure the height of the plants grown in different types of soil over a period of time. All plants used may may not start out at the same height, you just need to measure and record the initial height of each plant to determine changes in height.
- What types of soil will be used and is it available? Research the different types of soil and mix your own soil types by starting with potting soil (use for the Control Experiment) and adding varying amounts of sand, clay, etc…..
- What types of plants will you use?
When planning your investigation, identify all the variables that need to be controlled, which are variable that might affect the results, such as:
- The amount of water each plant receives; amount of light; the temperature of the environment;
- Type of plant;
- Type of container used, etc….
You want all the plants to have the same growing conditions except for one variable, the independent variable which is, different types of soil.
Repeating an experiment for a more reliable conclusion. When deciding on your experimental purpose, think ahead–Are all the supplies needed available and affordable? Since the experiment should be repeated 4 to 5 times (what ever is required), think about where you will set up the investigation as well as the types of plants to use for any plant investigation.