V ARIABLES IN S CIENCE

B RAINSTORM WITH A P ARTNER Where are places you’ve heard the word “variable” in your life? What does it mean?

B RAINSTORM WITH A P ARTNER Variable Clouds: the clouds will appear on and off (not all the time) Variable in math: an unknown Variable moods: apt to change or vary

N OTES Copy down anything that is in BOLD.

W HAT IS A V ARIABLE IN S CIENCE ? Variable are an important part of science. A variable is any factor that can be controlled or changed in an experiment. Scientific experiments have three types of variables.

I NDEPENDENT V ARIABLES The independent variable is the condition that you change in an experiment. Memory Tip: I control the Independent variable. Example: In an experiment measuring the effect of temperature on solubility, the independent variable is temperature. (Solubility will not change, but you can change the temperature.)

D EPENDENT V ARIABLE The dependent variable is the variable that you measure or observe. Memory Tip: The dependent variable gets its name because it is the factor that is dependent on the state of the independent variable. Example: In the experiment measuring the effect of temperature on solubility, solubility would be the dependent variable.

C ONTROLLED V ARIABLE A controlled variable or constant variable is a variable that does not change during an experiment.

V ARIABLES T HAT C AN B E M EASURED Time Mass Length Temperature Speed Volume Pressure Density Rainfall Wind speed Movement Size Boiling Point Freezing Point

E XAMPLE A scientist wants to see if the brightness of light has any effect on a moth being attracted to the light. Answer on next slide.

A scientist wants to see if the brightness of light has any effect on a moth being attracted to the light. Independent Variable: the brightness Dependent Variable: the moth’s attraction to the light

T RY T HESE A scientist studies the impact of a drug on cancer. A scientist studies the impact of witholding affection on rats. A scientist student how many days people can eat soup until they get sick of it.

A scientist studies the impact of a drug on cancer. IV: the dosage of the drug DV: the impact the drug has on cancer

A scientist studies the impact of witholding affection on rats. IV: the affection provided (or not provided) DV: the rat’s reaction

A scientist student how many days people can eat soup until they get sick. IV: the number of days of consuming soup DV: the onset of illness

T EST G ROUPS AND C ONTROL G ROUPS Scientists test their experiments with people by separating them into two groups. The test group receives the treatment (or experiment). The control group receives fake treatment (called a placebo). They do to find out how much of the treatment is in their mind, and how much of the treatment is actually working.

Example: if there is a new study to test out the effectiveness of a “miracle weightloss drug: The test group will receive the real drug. The control group will receive a fake pill. Both groups will be monitored. The control group is important. People may be more conscious about their food choices when they know they are being monitored. If the control group losses weight, it would be because they lost weight (it would have nothing to do with the “miracle drug.”)

N OTE Scientists do not tell participants which group they are in. Everyone is to assume they are in the test group.

A SSIGNMENT Complete the Simpson’s Worksheet Complete the Science Safety Worksheet (review from our science safety days).