Scientific Method Review

Kevin did an experiment where he took three groups of plants and gave them a different amount of fertilizer. Group 1 received no fertilizer, Group 2 got one teaspoon of fertilizer, and Group 3 received two teaspoons of fertilizer. All the plants received the same amount of water and were placed in the same location.

What were the independent and dependent variables in Kevin's experiment?

• The independent variable was the height of the plant, and the dependent variable was the type of plant used in the experiment.

• The independent variable was the height of the plant, and the dependent variable was the amount of fertilizer given to the plants.

• The independent variable was the amount of fertilizer given to the plant, and the dependent variable was the amount of water given to the plant.

• The independent variable was the amount of fertilizer given to the plants, and the dependent variable was the height of the plants.

Chap wanted to see if planting seeds deeper into the soil had an effect on plant height. He took ten containers and planted radish seeds at varying depths. He used the same type of soil, kept the plants in the same location, and gave them each 20 milliliters (mL) of water each day. Then, he measured the height of the sprouts every day for two weeks.

What are the independent and dependent variables in Chap's experiment?

• The independent variable is the height of the plants, and the dependent variable is the type of soil used.

• The independent variable is the plant height, and the dependent variable is the depth at which Chap planted the seeds.

• The independent variable is the depth at which Chap planted the seeds, and the dependent variable is the amount of water each plant received.

• The independent variable is the depth at which Chap planted the seeds, and the dependent variable is the plant height.

In scientific investigations, only one factor can be varied at a time. Other factors must be held constant. Students are investigating whether light color affects the height plants grow. Which factor must be held constant in the students' investigation?

• the color of light

• the amount of water

• the height plants grow

• the amount of sunlight outdoors

Wendy is interested in how producers and consumers interact in an ecosystem. She fills a 10-gallon fish tank with water and aquatic plants and introduces a population of snails. Her hypothesis is, "If the amount of aquatic plants in an ecosystem decreases, then snail death will be observed." Which of these research questions is best answered by Anjali's hypothesis?

• How many producers can an ecosystem support?

• Which predators limit populations within an ecosystem?

• How do scavengers affect organisms living within an ecosystem?

• How do producers affect the number of consumers within an ecosystem?

Saul notices that the sidewalks outside his apartment building are slippery during icy weather. He wants to use rock salt and calcium chloride. His hypothesis is that if calcium chloride is placed on ice, then it will melt ice in less time (in seconds) than rock salt.

What is the dependent variable?

• amount of rock salt

• amount of calcium chloride

• melt time

• amount of ice on sidewalk

This variable in an experiment is the one being deliberately changed by the scientist.

• data

• independent variable

• theory

• dependent variable

Should experiments be repeated over and over to see if the results are the same each time?

• yes

• no

The summary at the end of an experiment that explains the results.

• conclusion

• materials

• procedures

• hypothesis

In a controlled experiment, how many independent variables can be worked with at a time?

• one

• two or more

• none

• however many you want

A student is planning an experiment to find out how the height from which he drops a ball affects how high the ball bounces. The dependent variable is the _____.

• diameter of the ball

• bounce height

• amount of gravity

• drop height