What is a variable? The changing quantities in a science experiment.

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

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