A scientist was studying the effects of oil contamination on ocean seaweed. He thought that oil runoff from storm drains would keep seaweed from growing normally so he decided to do an experiment. He filled two tanks of equal size with water and monitored the dissolved oxygen and and temperature in each to be sure they were equal. He introduces some motor oil into one tank and then measured the growth of seaweed in the tank. In the tank with no oil, the average growth was 2.7cm. The average growth of the seaweed in the tank with the oil was 2.37cm. Based on this experiment:

Question

A scientist was studying the effects of oil contamination on ocean seaweed. He thought that oil runoff from storm drains would keep seaweed from growing normally so he decided to do an experiment. He filled two tanks of equal size with water and monitored the dissolved oxygen and and temperature in each to be sure they were equal. He introduces some motor oil into one tank and then measured the growth of seaweed in the tank. In the tank with no oil, the average growth was 2.7cm. The average growth of the seaweed in the tank with the oil was 2.37cm. Based on this experiment:

3. Identify the independent variable, the dependent variable, and the experimental controls

Answer: independent variable is motor oil
Dependent variable is growth of seaweed
Experimental controls:
Tanks, dissolved oxygen, and temperature

Answer 1

Correct! In this experiment, the independent variable is the motor oil because it is the factor that the scientist intentionally manipulates. The dependent variable is the growth of seaweed because it is the outcome that the scientist measures or observes to determine the effect of the independent variable.

The experimental controls in this case include the tanks themselves, as they need to be of equal size to ensure that the conditions are as similar as possible. Additionally, monitoring and ensuring equal levels of dissolved oxygen and temperature in both tanks are also considered experimental controls. These controls are necessary to minimize any potential confounding variables and to isolate the effect of the independent variable on the dependent variable.

Answer 2

That is correct! The independent variable in this experiment is the motor oil, as it is the factor being manipulated by the scientist. The dependent variable is the growth of seaweed, as it is the outcome that is being measured to determine the effect of the oil contamination. The experimental controls include the tanks used, as they are of equal size, as well as the monitoring of dissolved oxygen and temperature to ensure that they are equal in both tanks. These controls help ensure that any differences in the growth of seaweed can be attributed to the presence of motor oil.