Question

Scientists tested the effect of a fertilizer on the growth of plants. They had 2 sets of plants, Group A which gets fertilizer, water and sun and Group B which gets only water and sun (but in equal amounts to Group A).
1. Explain how this scenario is a controlled experiment and identify the manipulated variable.

2. If the scientists only performed 1 experiment but it supported their hypothesis, why can it not be considered a theory?

3. The graph below was created showing the growth of the plant. How would you know that the y-axis is measuring the growth of the plant?

Answer 1

1. This scenario is controlled due to the fact that they usually test the effect of fertilizer, water and sunlight. Two last points pose as explanation for the second part of question.
2. It can not be considered a theory because often it is supported by  hypothesis, so it's not direct thesis.
3. The way to know that the y-axis is measuring the growth of the plant is to look at the graph and see that it shows  plant growing up.