2. How Science works:Variables

3. About the different types of variables, How to identify them when doing your practical work. Learning Objectives You should learn :

4. Variables Variables are things that vary and change

5. Variables In any experiment there are 3 variables:  some control variables  an independent variable  a dependent variable Let’s look at each type….

6. Independent Variable This is the thing that you decide to change. o What is tested o What is manipulated

7. Dependent Variable This is the variable that changes as a result. It is the variable that you measure. o What is observed o What is measured o The data collected during the investigation

8. Controls These are all the variables that must not change, to make sure it is a fair test. Also called “CONSTANTS”

9. Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle. Example Situation Identify the independent, dependent, and control variables.

10. Independent variable This is the thing that you decide to change. You decide the ages to be tested, so: The ages of the students is the independent variable. The ages of the students Different ages were tested by the scientists

11. Dependent variable This is the variable that changes as a result. It is the variable that you measure. Which is the dependent variable here? The time it took to put the puzzle together The time was observed and measured by the scientist

12. Control Variables These are all the variables that must not change, to make sure it is a fair test. Same puzzle All of the participants were tested with the same puzzle It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

13. The higher the temperature of water, the faster an egg will boil. Another Example Situation Identify the independent, dependent, and control variables.

14. Variables Independent: the temperature of the water Dependent: time needed to cook the egg Controls: type of egg, stove, pots used

15. { MORE PRACTICE!!! Independent or Dependent? Can you figure it out?

16. The temperature of water was measured at different depths of a lake. ind. variable = _________________ dep. variable =_________________ depth temperature

17. Grass will grow taller if it is watered a great deal. ind. variable = _________________ dep. variable =_________________ water height

18. Lemon trees receiving the most water produce the largest lemons. ind. variable = _________________ dep. variable =_________________ amount of water size of lemons

19. More bushels of potatoes will be produced if the soil is fertilized more. ind. variable = _________________ dep. variable =_________________ amount of fertilizer number of potatoes

20. An investigation was done to see if keeping the lights on for different amounts of time each day affected the number of eggs chickens laid. ind. variable = _________________ dep. variable =_________________ time with light number of eggs

21. The amount of pollution produced by cars compared to the amount of lead in the gasoline. ind. variable = _________________ dep. variable =_________________ amount of lead pollution