Question

model 3 - aquatic plant data

	length of clipping (cm)	number of leaves on clipping	lamp power (watts)	percentage of light from lamp that reaches the plant	number of oxygen bubbles formed in 10 minutes
-------	-------------------------	------------------------------	--------------------	-----------------------------------------------------	------------------------------------------------		a	12		40	100%			b	12		40	75%			c	12		40	50%			d	12		40	25%

1. refer to the diagrams in model 2 to complete the data table in model 3.

1. the column headings in model 3 each describe a variable in the experiment.

a. what variable was purposely changed in the experiment?

b. what variable changed as a result of changing the variable listed in part a?

c. what variable(s) in the model 3 data table remained constant among all the trials?

Explanation:

Question 8a

In an experiment, the independent variable is the one that is purposely changed. Looking at the table, the "Percentage of light from lamp that reaches the plant" varies (100%, 75%, 50%, 25%) while other variables like length of clipping (12 cm for all) and lamp power (40 watts for all) are constant. So this is the independent variable.

The dependent variable changes as a result of the independent variable. The "Number of oxygen bubbles formed in 10 minutes" is expected to change based on the amount of light (independent variable), as light affects photosynthesis which produces oxygen bubbles.

Constants are variables that don't change across trials. The "Length of clipping (cm)" is 12 for all, "Lamp power (watts)" is 40 for all, and if we assume the "Number of leaves on clipping" is the same (since it's blank, implying constant), these are constant.

Answer:

Percentage of light from lamp that reaches the plant

Question 8b