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Scientific Variables Answer Key

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Scientific Variables Answer Key

Read each experiment carefully. Identify the independent variable (what is changed), the dependent variable (what is measured), and the constants (what is kept the same). Answers are shown with each question.

Identify the Variables

For each experiment, identify the independent variable, dependent variable, and at least three constants.

1.Chloe inflates identical bike tires to 30, 40, or 50 pounds per square inch (psi). She releases the same bike from the same ramp and measures its rolling distance. Identify the independent variable, dependent variable, and three constants.

2.Malik tests whether different bicycle chain lubricants affect how long a wheel keeps spinning. He uses the same wheel, applies the same amount of each lubricant, and times each spin. Name the independent variable and the dependent variable.

3.A mechanic tests two bike bells by measuring how far away each can be heard. Give three conditions that should be kept the same for a fair comparison.

Check Your Understanding

Choose the best answer for each item.

4.In an experiment, what is the independent variable?

The factor deliberately changed
The result that is measured
A factor kept the same
The conclusion drawn at the end

5.A student compares three seat heights and records how long it takes to ride a short course. What is the dependent variable?

The seat height
The time to ride the course
The bicycle color
The number of course markers

6.Which set of conditions should stay constant when testing whether tire pressure changes rolling distance?

Tire pressure and rolling distance
Bike, ramp, and release method
The result and the conclusion
The pressure and the ramp height

7.For a test of how different bike light settings affect battery life, mark each factor as independent variable, dependent variable, or constant: light setting; hours until the battery runs out; same battery type.

Light setting
Hours until the battery runs out
Same battery type

Dependent variable
Constant
Independent variable

8.True or false: A fair test changes one independent variable at a time and keeps other important conditions the same.

TrueFalse

9.Complete the sentence: The variable that a scientist measures to find out what happened is the variable.

Plan and Evaluate a Fair Test

Use the clues in each question to reason about a test design.

10.Elijah wants to test whether the width of a bike tire affects how far a bike rolls. Write a testable question, name the independent and dependent variables, and list three constants.

11.Chloe tests how different handlebar grips affect comfort. She changes the grip material and also rides each trial on a different route. What is one problem with this test, and how could she improve it?

12.A student compares two bike pumps in one trial each. Give one reason to repeat each trial several times.