How Science works Variables Learning Objectives You should

How Science works: Variables

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

Variables are things that vary and change

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

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

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

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

Example Situation 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. Identify the independent, and control variables.

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

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

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.

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

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

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

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

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

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

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

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. time with light ind. variable = _________ number of eggs =_________ dep. variable =_________

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