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Scientific Scientific MethodMethod

Scientific Method Scientific Method

and and

Controlled ExperimentsControlled Experiments

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Science and the Science and the Scientific MethodScientific Method

ScienceScience is a way of learning about is a way of learning about the natural world and the the natural world and the knowledge gained through that knowledge gained through that processprocess

The Scientific MethodThe Scientific Method also called also called scientific inquiryscientific inquiry is the diverse is the diverse ways in which scientists explore ways in which scientists explore problems and seek to answer problems and seek to answer questions about the natural world.questions about the natural world.

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The Steps of the The Steps of the Scientific MethodScientific Method

1. Posing Questions1. Posing Questions2. Developing a Hypothesis2. Developing a Hypothesis3. Designing an Experiment3. Designing an Experiment4. Interpreting Data4. Interpreting Data5. Drawing Conclusions5. Drawing Conclusions

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Posing QuestionsPosing Questions

Experiments begin by asking Experiments begin by asking a scientific question which is a scientific question which is a question that can be a question that can be answered by gathering answered by gathering evidence. An example is evidence. An example is “Which freezes faster– “Which freezes faster– freshwater or salt water?”freshwater or salt water?”

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Developing a Developing a HypothesisHypothesis

A A hypothesishypothesis is a possible explanation is a possible explanation for a set of observations or it can be an for a set of observations or it can be an answer to a scientific question. A answer to a scientific question. A hypothesis must be something that can hypothesis must be something that can be tested. A hypothesis can be written be tested. A hypothesis can be written in the form of an in the form of an If....then....If....then.... Statement. An example is Statement. An example is “If I add salt “If I add salt to fresh water, then it will take longer to fresh water, then it will take longer to freeze.”to freeze.”

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Designing an Designing an ExperimentExperiment An experiment should have only one An experiment should have only one

variable that changes. Experiments variable that changes. Experiments have have variablesvariables which are any factors which are any factors that can change in an experimentthat can change in an experiment

The The manipulated variable (or manipulated variable (or independent variable)independent variable) is the one is the one factor that you change in the factor that you change in the experimentexperiment

The The responding variable (or responding variable (or dependent variable) dependent variable) is the factor is the factor that changes as a result of the that changes as a result of the manipulated variable, it is what you manipulated variable, it is what you measure to obtain you resultsmeasure to obtain you results

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Designing an Designing an ExperimentExperiment

In aIn a controlled controlled experiment experiment all all factors except one are kept constantfactors except one are kept constant

Controlled variables Controlled variables are variables are variables that are kept constant among all of that are kept constant among all of the tested subjects of the experiment.the tested subjects of the experiment.

Most controlled experiments include Most controlled experiments include a a control group control group or or control control subjectssubjects which are subjects that do which are subjects that do not experience changes to the the not experience changes to the the manipulated variable but are kept at manipulated variable but are kept at normal conditionsnormal conditions

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Interpreting DataInterpreting Data The observations and measurements The observations and measurements

made during an experiment are called made during an experiment are called datadata. After conducting an experiment . After conducting an experiment scientists analyze the data to look for scientists analyze the data to look for patterns or trends. Data is often patterns or trends. Data is often organized in a data table or graph to organized in a data table or graph to identify patterns and trends easieridentify patterns and trends easier

Scientists ask: Does the data support the Scientists ask: Does the data support the hypothesis? Do they need to collect hypothesis? Do they need to collect more data?more data?

Is there a flaw in the experiment?Is there a flaw in the experiment?

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Drawing Drawing ConclusionsConclusions

A A conclusionconclusion is a statement that is a statement that sums up what you have learned from sums up what you have learned from an experiment. When scientists an experiment. When scientists draw a conclusion they need to draw a conclusion they need to decide whether the data collected decide whether the data collected supports their hypothesis or not. An supports their hypothesis or not. An experiment may need to be repeated experiment may need to be repeated several times before a conclusion several times before a conclusion can be drawn.can be drawn.

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Hypothetical ExperimentHypothetical Experiment If I want to see if adding fertilizer to If I want to see if adding fertilizer to

plants helps them grow faster…plants helps them grow faster… What would be the manipulated What would be the manipulated

variable?variable?The amount of fertilizer added to plantsThe amount of fertilizer added to plants

What should be some controlled What should be some controlled variables?variables?

Type of plantsType of plants Amount of water givenAmount of water given Amount and intensity of sunlight exposureAmount and intensity of sunlight exposure Type of soil planted inType of soil planted in Type of pot planted inType of pot planted in

Ambient temperatureAmbient temperature