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Scientific Method

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Beginnings

• Aristotle (384 BCE-322 BCE or BC)• ancient Greek philosopher

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Aristotle

• Aristotle, more than any other thinker, determined the orientation and the content of Western intellectual history. He was the author of a philosophical and scientific system that through the centuries became the support and vehicle for both medieval Christian and Islamic scholastic thought: until the end of the 17th century, Western culture was Aristotelian. And, even after the intellectual revolutions of centuries to follow, Aristotelian concepts and ideas remained embedded in Western thinking.

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• In other words, Aristotle was so famous that his work influenced thinking in the Western world from his time to the present.

• This was fine when he was right. But he was so influential that his mistakes were never noticed.

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• Aristotle and his contemporaries believed that all problems could be solved by thinking about them.

• Sometimes this worked, other times it did not.

• For example, Aristotle thought that heavy objects would fall faster than lighter ones.

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• Now that does seem reasonable at first. And this is how “science” was done in ancient times.

• But what did Aristotle not do?• He never tested his ideas!• The world would have to wait almost

2000 years for that to happen.

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Galileo Galilei

•1564-1642 AD or CE

•Lived in what is today Italy

•Is considered to be the first true scientist.

•Why????

•Because he actually tested his ideas.

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• Aristotle said that heavy objects fall faster than lighter ones.

• So Galileo asked, “How much faster?”• So he sent students up to the top of a

building and had them drop a heavy ball and a lighter one off at the same time. He had other students waiting below to measure the difference in time between the two hitting the ground.

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• Today of course we know what happened.• Much to everyone’s surprise both balls hit

the ground at about the same time!• This shows that it is much preferred to test

your ideas rather than merely think about them.

• One test is worth a thousand expert opinions. Bill Nye

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Scientific Method Steps

• Observe a situation• State the problem.• Make a hypothesis.• Conduct the experiment.• Record/analyze data.• Draw a conclusion.

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Hypothesis

• An educated guess or prediction• Use “If”, “then”, “because” format• We predict that if we drop a ball

from a higher height, then it will bounce higher, because heavier objects fall faster than lighter objects.

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Variables and Controls

• When conducting an experiment, change one factor and keep everything else exactly the same.

• The one thing you change is called the variable.

• All the things you keep the same are called controls.

• “If” is the independent variable.• “Then” is the dependent variable.

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Galileo’s Experiment

• What was the independent variable in Galileo’s experiment?

• The weight of the balls.• What was the dependent variable in

experiment?• The speed they fall.

• What were some controls?• Dropped from same height.• Dropped at same time.• Balls had same shape/size.

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ReviewVariable: theone thing youchange in anexperiment.

Data: theinformation youget when youtest thevariable.

Controls: theparts of theexperiment thatstay the same.

Manipulatedvariable: youchange thisyourself.

Respondingvariable:responds to thechange youmade.

Controllingvariables

I ndependentvariable: on itsown.

Dependantvariable:depends on thechange youmade.

Controllingvariables

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Observations

• Observations: We use our senses to gather information about the world around us. There are two types of observations.

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Qualitative

• Qualitative observation: (quality) Usually made with our senses.

• Color, shape, feel, taste, sound.• Olivia is wearing a blue sweater.• The lab tabletop is smooth.• The dog’s fur is shiny.

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Quantitative

• Quantitative observation: (quantity) How many. Will always have a number.

• Based on exact measurement.• The room is 8 meters across.• Sarah is 141-cm tall.• Sam weighs 450

Newtons.

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Inferences

• Inference:• A logical interpretation of an event

that is based on observations and prior knowledge.

• What does this mean in 6th grade terms?

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Making Inferences

• You are at the counter in the office to get a bus pass signed. You see a student leave the principal’s office crying and upset. We could make an inference as to why the student is upset.

• Could be in trouble (ISS, OSS, expelled)• Family problems at home (sick, accident)• Student not feeling well• Student has poor grades (failing,

retention)

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Theory

• Has a very different meaning in science than in everyday life.

• “The detective has a theory about who robbed the bank.” This is a guess.

• When scientists use the word theory it is not used as a guess.

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Theory defined

• An explanation based on many observations during repeated experiments that is valid only if it is consistent with observations, makes predictions that can be tested, and is the simplest explanation.

• A logical, time tested explanation for events that occur in nature.

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• So the theory of gravity, theory of electricity, the germ theory of disease, and the theory of evolution are tested, accepted explanations for events that occur in nature.

• Theories can really never be completely proven, only disproven. When new evidence comes along, we must modify our theory or at times even get rid of it and start over again.

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• Ptolemy’s earth centered theory of the solar system is an example of what can happen when new evidence comes along. When Copernicus showed that putting the Sun in the center made it much easier to predict the planets motions, the old earth centered theory was discarded and a new one developed.

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Graphing

• Graphs are a useful tool in science.• The visual characteristics of a graph make

trends in data easy to see. • One of the most valuable uses for graphs is to

"predict" data that is not measured on the graph.

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Graphing Steps

• Identify the Variables• Determine the range• Determine the scale• Number and label each axis• Plot the points• Draw the graph• Give your graph a title

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Identify the Variables

– Independent Variable - (the thing you changed)

· Goes on the X axis (horizontal) · Should be on the left side of a data

table.

– Dependent Variable - (changes with the independent variable)

· Goes on the Y axis (vertical) · Should be on the right side of a data

table.

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Range

– Subtract the lowest data value from the highest data value.

– Do each variable separately.

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Scale

– Determine a scale,(the numerical value for each square),that best fits the range of each variable.

– Spread the graph to use MOST of the available space.

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Label Axis's

• You need to tell everyone reading your graph what the graph means.

• Be sure to include units.

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Plotting

• Plot each data value on the graph with a dot. You can put the data number by the dot, if it does not clutter your graph.

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Drawing

–Draw a curve or a line that best fits the data points.

–Most graphs of experimental data are not drawn as "connect-the-dots".

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Title

• Your title should clearly tell what the graph is about.

• If your graph has more than one set of data, provide a "key" to identify the different lines

• While your high school teachers might not like it, I do like putting your name in the title of the graph.

• Rachel and Max’s Sunspot Graph

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Interpolation

• Interpolate: predicting data between two measured points on the graph.

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Extrapolation

• Extrapolate: extending the graph, along the same slope, above or below measured data.

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Operational Definition• A very clear and very precise explanation of the items being

measured.

• A method to ensure that anyone making the measurement will get the same answer.

• Basically you are deciding how each variable is being measured.

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How will we measure?

• In the Bouncing Ball Lab we are measuring how high the ball bounces when dropped.

• But where do we measure to?

• The bottom. Top, or middle of the ball?

• It makes a difference.

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Our Definition

• We will all measure from the floor to the bottom of the ball.

• This way we will get consistent results.