VARIABLES

Variables Factors in an experiment that can change.

VARIABLES

Controlled VariableAlso called a “Control or Constant.”A factor or condition that stays the same in an experiment.

VARIABLES

Independent VariableAlso called a “Manipulated Variable” Think… I CHANGE this variable (I as in you)

A factor or condition that is intentionally changed by the investigator in an experiment.

The factor you wish to test!

VARIABLES

Dependent VariableAlso called a “Responding Variable”Think… DEPENDS on what I change (I as in you)

A factor or condition that might be affected as a result of change in the independent variable.

Factor you measure to gather results!

VARIABLES

Controlling VariablesKeeping all conditions the same except for the independent variable.

VARIABLES

Example:Imagine an experiment to test how air temperature affects the rate at which ice melts.What is the independent variable?What is the dependent variable?What are the controlled variables?

VARIABLES

Independent Variable: Air Temperature

Dependent Variable: Rate at which the ice melts

Controlled Variables:Amount of iceShape of iceType of container

VARIABLES

J im, Jody, and Juan, all sixth graders, love to play tennis and are interested in forming an interscholastic tennis team. To do so, they decide to hold tennis practice sessions during period 4 every day. Mr. M, Mr. P, and Mr. S agree to hold tryouts at the end of October. Seeing as how this was their idea, Jim, Jody, and Juan want to make sure that they will make the team. To ensure their placement on the team, they test to see which brand of tennis ball helps produce the fastest serve. Jim, Jody, and Juan believe that if they determine the ball that produces the fastest serve, they will defi nitely make the tennis team because they will have an advantage over the other players. Before completing the experiment, they all think that brand X tennis balls will bounce the highest because they are the hardest to squeeze. Using brand X, Y, and Z tennis balls, they decide to drop each ball from 15 meters above the ground onto a clay tennis court. They measure the height that each ball bounces and record this value in their data table. J im, Jody, and Juan complete fi ve trials for each tennis ball and record an average height in their data table.

SAMPLE READING #1: SCIENTIFIC SERVES BY CHRIS SHAYER

What is the independent variable in the experiment?

What is the dependent variable in the experiment?

According to the passage, what was their hypothesis?

Name three constants involved in the experiment.

SAMPLE READING #1: SCIENTIFIC SERVES BY CHRIS SHAYER

Alberta, Megan, and Tom are trying to grow the largest pumpkin for the state fair. They decide to use the greenhouse behind Mr. K’s room. They want to test which type of soil is best suited for growing pumpkins. Alberta, Megan, and Tom decide that if they can determine which type of soil is best suited to grow pumpkins, they will win the blue ribbon. Before completing the tests, they all think that potting soil will work the best because it contains plenty of organic material, which helps the soil hold water. They plant pumpkin seeds in regular dirt dug from behind the school, sandy soil found at Megan’s house, and store-bought potting soil. They fi ll three clay pots with the regular dirt and label them Pot A, Pot B, and Pot C. They also fi ll three clay pots with the sandy soil and label them Pot A, Pot B, and Pot C. Finally, they fi ll three clay pots the potting soil and label them Pot A, Pot B, and Pot C. In each pot, they plant the same species of pumpkin seed, water them with the same amount of water, and place them in the greenhouse so that they all get the same amount of sunlight. After the pumpkins grow, they measure how much each pumpkin weighs from each type of soil and record their fi ndings.

SAMPLE READING #2: PERFECT PUMPKINS BY DINA ROSSI

What is the independent variable in the experiment?

What is the dependent variable in the experiment?

What was the hypothesis that Alberta, Megan, and Tom came up with in their experiment?

What are three constants in this experiment?

SAMPLE READING #2: PERFECT PUMPKINS BY DINA ROSSI

Timmy, Tommy, and Tina want to plant a garden at their middle school. They have written a letter to Mr. B asking permission to use the land around school for their garden. Mr. B has agreed, but they can only use one area of the property for the garden. Before picking a spot, Tina, Tommy, and Timmy walk around the school to fi nd the perfect location for the garden. Tina l ikes the spot behind the tennis courts, Tommy l ikes the spot behind the cafeteria, and Timmy wants the garden in the front of the school. Al l three of these areas are fl at and receive the same amount of sunl ight. Tina remembers working in the summer on her grandparents’ farm and her grandfather always saying, “To have a good crop you need good soi l that holds lots of water.” To be fair to al l , they agree to take samples of the soi l at each spot and to perform an absorbency test to see which soi l holds the most water. After taking the soi l samples, they fi nd that the front of the school has very sandy soi l , the area around the tennis courts is made up of a clay-based soi l , and the area behind the school consists of soi l that contains decomposed organic materials from leaves, twigs, and grass cl ippings. After looking at the diff erent types of soi ls, they al l think that the clay-based soi l wi l l hold the most water and that the area behind the tennis courts wi l l be the best place for the garden. To test for absorbency of the water, they place 50 g of each soi l into a funnel with fi lter paper. Underneath the funnel is a beaker that wil l catch the water that seeps through the soi l . Next, they pour 100 mL of water into the soi l and record the amount of water fi ltered and absorbed. They test each soi l fi ve t imes to be sure that their results are accurate.

SAMPLE READING #3: SOIL ABSORPTION BY STEVE MATYCZYK

What is the independent variable in the experiment?

What is the dependent variable in the experiment?

What was the hypothesis that Timmy, Tommy, and Tina came up with in their experiment?

What are three constants in this experiment?

SAMPLE READING #3: SOIL ABSORPTION BY STEVE MATYCZYK

“ I fee l that the sand wi l l erode the least ,” s tated J im. J im and Sa l ly were hav ing a d iscuss ion about which type o f sed iment that made up the bed o f Wakoo ie St ream would erode the least over t ime. “ I th ink the smal l rocks at the bottom of the s t ream wi l l e rode the least because they are heav ier than the sand,” sa id Sa l ly. “The sand i s go ing to erode the least because i t i s packed at the bottom of the s t ream, g iv ing the sand part ic les extra s t rength to s tay in p lace. I ’m correct and you are wrong!” sa id J im. J im and Sa l ly decided to invest igate which type o f par t ic le at the bottom of Wakoo ie St ream would erode the least . J im and Sa l ly developed a test to see who was r ight . J im and Sa l ly took three d iff erent sed iments f rom the s t reambed: sand part ic les , smal l rock par t ic les , and large rock par t ic les . They co l lected 100 mL o f each sed iment . Next , J im and Sa l ly took a 4- foot p last ic conta iner onto three b locks o f wood that measured 5 inches in he ight . Th is created a ramp. Seven inches f rom the top o f the ramp, Sa l ly drew a square box . The square box that Sa l ly drew was where they would p lace the sed iment dur ing each t r ia l . Meanwhi le , J im measured 1 ,000 mL o f tap water. J im and Sa l ly d id the exper iment once the mater ia ls were co l lected. Fi rs t they p laced the 100 mL o f sand sed iment in the square that was drawn by Sa l ly. Then they poured the 1 ,000 mL o f tap water f rom the top o f the conta iner , a l lowing the tap water to run into the sed iment as i t t rave led downhi l l . The water was act ing l i ke the fl ow of a s t ream in th is invest igat ion . When the water came to a s top at the bottom of the conta iner , Sa l ly and J im p laced the so i l that d id not wash away ( the so i l remain ing in the square Sa l ly drew) in to a 100 mL beaker and measured how much so i l had been eroded away. Each type o f sed iment was test three t imes in th is manner. After each t r ia l was conducted, J im and Sa l ly found the average for how much so i l eroded away and d iscovered which sed iment eroded the least and which sed iment eroded the most .

SAMPLE READING #4: STREAMBED EROSION BY SHAWN PELLETIER

What is the independent variable in the experiment?

What is the dependent variable in the experiment?

What was Jim’s hypothesis in the experiment?

What are three constants in this experiment?

SAMPLE READING #4: STREAMBED EROSION BY SHAWN PELLETIER