1. Variables Notes Nature of Science Unit See corresponding notes to fill in blanks for completion then paste into composition/lab notebook Mr. Ben Thompson 7 th Grade Science Fulbright Jr. High Bentonville, Arkansas

2. Variables Variable – a factor that can change in an experiment Controlled Experiment – experiment where only one variable is changed Independent Variable – (also called manipulated variable) the variable that is changed on purpose in an experiment – what do I change?

3. Variables Dependent Variable – (also called responding variable) the variable that changes in response to the independent variable – what do I observe/measure? Controlled Variable – (also called a Constant) – a variable that must be kept the same throughout the entire experiment – what do I keep the same? The Control – the part of the experiment that remains unchanged and is used to detect and measure any effects of unknown variables

4. Hypothesis Hypothesis – a possible explanation for a question or problem (an educated prediction) IF......THEN……statement Must be testable!

5. DRYDRY ependent esponding - Axis anipulated ndependent M IX X - axis Y - axis

6. Mean, Median, Mode, Range Mean – add all of the numbers and divide by the total number of numbers in the list. Median – the middle number in a list of numbers when ordered smallest to largest. Mode – the number that appears most often in a list of numbers. Range – the difference between the largest and smallest number in a list of numbers. Subtract the smallest number from the largest number.

7. Esther became interested in insulation while her parent’s new house was being built. She decided to determine which insulation transferred the least heat. She filled each of 5 jars half-full with water. She sealed each jar with a plastic lid. Then she wrapped 4 jars with a different type of insulation and left 1 jar with no insulation. She thinks the thicker insulation will transfer less heat. She put the jars outside in the direct sunlight. Later, she measured the temperature of the water in each jar. Identifying Variables - Practice

8. Sandy heard that plants compete for space. She decided to test this idea. She bought a mixture of flower seeds and some potting soil. Into each of 5 plastic cups she put the same amount of soil. In the first cup she planted 2 seeds, in the second cup she planted 4 seeds, in the third cup 8 seeds, and in the fourth cup she planted 16 seeds. In the last cup she planted 32 seeds. After 25 days, she determined which set of plants was the tallest. Identifying Variables - Practice

9. Jack wanted to test which brand of car wax was most effective. He tested three brands of wax. He cleaned the hood of his car and removed the old wax. He measured four equal sections on the hood of the car. Each of the waxes was used to cover a section. An equal amount of wax, the same type of rag, and equal buffing were used. Five drops of water were placed on each square, and the diameter of each drop was measured (cm). Jack used a qualitative dependent variable by developing a rating scale for amount of shine, from dull to very shiny. Identifying Variables - Practice

10. Variables Variable – a factor that can change in an experiment Controlled Experiment – experiment where only one variable is changed Independent Variable – (also called manipulated variable) the variable that is changed on purpose in an experiment to test a hypothesis– what do I change? Dependent Variable – (also called responding variable) the variable that changes in response to the independent variable – what do I observe/measure? Controlled Variable – (also called a Constant) – a variable that must be kept the same throughout the entire experiment – what do I keep the same?

11. Example: An experiment was being done to test fertilizers A & B in order to see which one makes grass grow faster. What are some variables? the type of fertilizer how much you water the grass how much fertilizer you use how big of a yard you have how much sunlight the yard gets the type of grass How would you make this a controlled experiment? use the same amount of water same size of yard same amount of fertilizer make sure they get the same amount of sunlight use same type of grass

12. Example: An experiment was being done to test fertilizers A & B in order to see which one makes grass grow faster. What is the independent variable? also called the… it’s what you change on purpose in this case it’s the fertilizer type; A or B What is the dependent variable? also called the… it’s the variable that changes in response to the independent variable in this case it’s how fast the grass grows. Manipulated Variable Responding Variable

13. Example: An experiment was being done to test fertilizers A & B in order to see which one makes grass grow faster. What would be some controlled variables? variables that must be kept the same amount of water size of yard type of grass amount of sunlight What would be the control? the experiment would need a portion of the yard that no fertilizer was used on to make sure that the fertilizers work at all!