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SCIENTIFIC EXPERIMENTS
One of the skills a scientist needs is the ability to analyze the experiments performed by others. Knowing what
makes an experiment scientifically beneficial enables scientists to determine if the conclusions reached are
valid.
A scientist wanted to determine the effects of different colored lights on plant growth. To do this, the
scientist sets up two experiments. One plant was grown under blue light and the other under red light. Below
are illustrations of the experiments. Study the illustrations and answer the questions below.
Red light
1 liter
Blue light
0.5 liter
20 °C
15°C
Rose
Lily
Time of experiment: 1 week
Amount of growth: 10 cm
Time of experiment: 1 week
Amount of growth: 5 cm
1. The scientist concluded that plants grow better under red light. Comment on this conclusion (was this a valid
experimental conclusion?).
2. In the space below, sketch the design an experiment similar to the one above that would make the
experiment more scientifically accurate. Then, describe the variables in questions 3 - 12.
3. light__________________________________
8. light__________________________________
4. temperature ____________________________
9. temperature ____________________________
5. water _________________________________
10. water _________________________________
6. time __________________________________
11 time _________________________________
7. plant _________________________________
12. plant ________________________________
State the hypothesis for the experiment you designed.
A group of students conducted an experiment to study the growth of bean plants. An equal number of bean
plants of similar size were planted in containers A and B. Each day for five days, Container A received water
only, while Container B received an equal amount of weak fertilizer solution. The table below shows the
average height of the plants in each container for each day of the experiment.
Which of these is being tested in this experiment?
1. effect of water on plant height
2. effect of fertilizer on plant height
3. maximum height the plants will grow
4. number of days the plants will grow
Read the description of the experiment and use the table of results below to answer the following question.
A student designed an experiment to see if plants grow better when watered with a sugar solution. He
divided the plants into six groups, measured the initial height of each plant, and calculated the average height
for each group. Once a week for two months, he watered the plants in each group using a different sugar
solution for each plant group. At the end of two months, he measured the final height of each plant and
calculated the average height for each group. The student’s data are shown in the table below.
Which of these statements explains why the plants in Groups E and F died?
1. The high sugar content caused too much water to move out of the root cells.
2. The high sugar content caused too much water to move into the root cells.
3. The high sugar content prevented the plant from capturing energy.
4. The high sugar content clogged the pores in the cell membranes.
Anna conducted an experiment using green algae. She put equal amounts of water into two identical
containers and maintained the water level throughout the experiment. Next she added equal amounts of green
algae to both containers. Container 1 received full sunlight while Container 2 was placed in the dark.
After two weeks, what will Anna most likely find in Containers 1 and 2?
1. no algae in either container
2. abundant algae in both containers
3. no algae in Container 1 and abundant algae in Container 2
4. abundant algae in Container 1 and no algae in Container 2