Question

1. amal is designing an experiment to test the effect of varying amounts of light on the rate of photosynthesis. he hypothesizes that the amount of oxygen produced is related to the amount of light a plant receives. he plans to use four plants of the same species and size. he will expose three of the plants to light for different lengths of time. the fourth plant will receive no sunlight at all. he will measure oxygen production for all four plants. what is the purpose of the fourth plant?

a. the fourth plant is a spare.
b. the fourth plant is the control.
c. the fourth plant is the test variable (independent variable).
d. the fourth plant is the outcome variable (dependent variable).

1. chandra has three pieces of metal with equal masses. each piece is the same color but has a different shape. she suspects that all three pieces are made of the same element, so she decides to measure the volume of each piece. which hypothesis is she most likely testing?

a. if the pieces of metal have the same volume, then they are all made of the same element.
b. if the pieces of metal have different volumes, then they are all made of the same element.
c. if the pieces of metal have the same volume, then each piece is made of a different element.
d. if the pieces of metal have different volumes, then each piece is made of a mixture of elements.

1. tracy performed an experiment on the effect of temperature on the rate of photosynthesis in plants during the day. she included the following graph in her lab report.

what other information does she need to include?
a. units
c. a legend
b. a title
d. axis labels

Explanation:

• Question 4: In an experiment, a control group is not exposed to the variable being tested. Here, the fourth plant receiving no sunlight serves as the control to compare the effects of different light - exposure levels on oxygen production in the other plants.
• Question 5: Chandra suspects the metal pieces are of the same element and measures volume. The hypothesis is likely that if the volumes are the same, they are of the same element, as density (mass/volume) is characteristic of an element and equal - mass pieces with equal volume would have the same density.
• Question 6: A graph in a lab report should have axis labels to clearly indicate what each axis represents. The given graph has time on the x - axis and temperature on the y - axis, but without labels it is not clear what the temperature values correspond to in terms of the photosynthesis experiment.

Answer:

1. B. The fourth plant is the control.
2. A. If the pieces of metal have the same volume, then they are all made of the same element.
3. D. axis labels