# Aim:How is the scientific method used to design experiments?

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Aim:How is the scientific method used to design experiments?. Do now: Observe the picture and make two observations about it. Vocabulary: Scientific method, experiment,variables. Scientific method. Experiment. - PowerPoint PPT Presentation

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How do scientists investigate the world?

Aim:How is the scientific method used to design experiments?

Do now: Observe the picture and maketwo observations about itVocabulary: Scientific method, experiment,variablesScientific method

Experiment Scientists use an experiment to search forcause and effectrelationships in nature. In other words, they design an experiment so that changes to one item cause something else to change. These changing quantities are calledvariables. Three kinds of variables: independent, dependent, and controlled.

Theindependent variableis the one that is changed by the scientist. A good experiment has only one independent variable. As the scientist changes the independent variable, he observeswhat happens to the dependent variable. Thus, the dependent variables are the results of the experiment. In a controlled experiment all quantities remain constant ans is used for comparison.QuestionIndependent Variable(What I change)Dependent Variables(What I observe)Controlled Variables(What I keep the same)How much water flows through a faucet at different openings?Water faucet opening (closed, half open, fully open)Amount of water flowing measured in liters per minuteThe FaucetWater pressure, or how much the water is "pushing""Different water pressure might also cause different amounts of water to flow and different faucets may behave differently, so to insure a fair test I want to keep the water pressure and the faucet the same for each faucet opening that I test."Does fertilizer make a plant grow bigger?Amount of fertilizer measured in gramsGrowth of the plant measured by its heightGrowth of the plant measured by the number of leavesSee Measuring Plant Growthfor more ways to measure plant growthSame size pot for each plantSame type of plant in each potSame type and amount of soil in each potSame amount of water and lightMake measurements of growth for each plant at the same time"The many variables above can each change how fast a plant grows, so to insure a fair test of the fertilizer, each of them must be kept the same for every pot."What Makes for Good Variables?For Good Variables, You Should Answer "Yes" to Every QuestionIs the independent variable measurable?Yes / NoCan you change the independent variable during the experiment?Yes / NoHave you identified all relevant dependent variables, and are they all caused by and dependent on the independent variable?Yes / NoAre all dependent variable(s) measurable?Yes / NoHave you identified all relevant controlled variables?Yes / NoCan all controlled variables be held at a steady value during the experiment?Yes / No