What is a variable?What is a

variable?

The changing quantities in a

science experiment.

Experiments have three

kinds of variables: •Independent •Dependent•Control or Constants

Variables in an experiment• Independent Variable: (MANIPULATED Variable)

- variable being changed/tested by the person.

- The variable that “I” Changed…

- Graphed on the X-axis

• Dependent Variable: (RESPONDING variable)

- variable that is measured; it is the result of the change of the independent variable

- it responds to the independent variable.

- Graphed on the Y-axis

DRY MIX

y-axis

x-axis

Dependent Variable

Responding Variable

Independent Variable

Manipulated Variable

Types of Graphs

• Bar – to compare data

• Line – to show data over a period of time

• Pie – percentages or parts of a whole

Controls or Constants

Constants are factors in the experiment that the scientist wants to keep

the same.

Here are a few examples . . .

Question:How much water can flow through

a faucet?Independent

Variable?Dependent Variable?

How much you open the faucet:•half open•closed•all the way open

How much water comes

out of the faucet,

measured in liters per minute.

Question:Does more fertilizer make a plant

grow bigger?Independent

Variable?Dependent Variable?

Constants?

Amount of fertilizer measured

in grams.

Growth of plant by height or number

of leaves . . .

•Same pot type•Same soil•Same sunlight•Same seeds

Question:Does heating a cup of water allow it to

dissolve more sugar?

Independent Variable?

Constants?

Dependent Variable?

Temperature of the water, measured in

Celsius.

Amount of sugar that dissolves completely in the water. Measured in

grams.

•Same amount of water•Same type of sugar•Stirring same in each

Question:Does an electric motor turn faster if you

increase the voltage?

Independent Variable?

Constants?

Dependent Variable?

Voltage of electricity, measured in volts.

Speed of the motor measured in rotations

per minute.

Same motor for tests