scienific method

7/29/2019 scienific method

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Scientific Method

Beginnings

• Aristotle (384 BCE-322 BCE or BC)

• ancient Greek philosopher

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 throughthe centuries became the support and vehicle for

both medieval Christian and Islamic scholastic

thought: until the end of the 17 th century, Western

culture was Aristotelian. And, even after the

intellectual revolutions of centuries to follow,

Aristotelian concepts and ideas remained

embedded in Western thinking.

• In other words, Aristotle was sofamous that his work influenced

thinking in the Western world fromhis time to the present.

• This was fine when he was right. But

he was so influential that hismistakes were never noticed.

• Aristotle and his contemporariesbelieved that all problems could be

solved by thinking about them.• Sometimes this worked, other times

it did not.

• For example, Aristotle thought thatheavy objects would fall faster thanlighter ones.

• Now that does seem reasonable atfirst. 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 almost2000 years for that to happen.

Galileo Galilei•1564-1642 AD or CE

•Lived in what is todayItaly

•Is considered to bethe first true scientist.

•Why????•Because he actually didthe experiment.

• Aristotle said that heavy objects fallfaster than lighter ones.

• So Galileo asked, “How much faster?”

• So he sent students up to the top ofa building and had them drop a heavyball and a lighter one off at the same

time. He had other students waitingbelow to measure the difference intime between the two hitting the

ground.

• 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 thinkabout them.

• One test is worth a thousand expertopinions. Bill Nye

Key Idea

• 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 arecalled controls.

Galileo’s Experiment

• What was the variable in Galileo’sexperiment?

• The weight of the balls.• What were some controls?

• Dropped from same height.

• Dropped at same time.

• Balls had same shape/size.

ReviewVariable: the

one thing you

change in an

experiment.

Data: the

information you

get when you

test the

variable.

Controls: the

parts of the

experiment that

stay the same.

Manipulated

variable: you

change this

yourself.

Responding

variable:

responds to the

change you

Controlling

variables

Independent

variable: on its

Dependant

variable:

depends on the

change you

Controlling

variables

Scientific Method Steps

• State the problem.

• Make a hypothesis.

• Conduct the experiment.

• Record/analyze data.

• Make a conclusion.• Report findings to others so they canrepeat the experiment.

Hypothesis

• An educated guess

• a prediction

• Use “If”, “then” format

• We predict that if we drop a ballfrom a higher height, then it willbounce higher.

• “If” is the manipulated variable.

• “Then” is the responding variable.

Observations

• Observations: We use our senses togather information about the world

around us. There are two types ofobservations.

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.

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.

Inferences

• Inference:

• A logical interpretation of an event

that is based on observations andprior knowledge.

• What does this mean in 6th grade

terms?

Making Inferences

• You are at the counter in the office to get abus pass signed. You see a student leave the

principal’s office crying and upset. We couldmake an inference as to why the student isupset.

• Could be in trouble (ISS, OSS, expelled)

• Family problems at home (sick, accident)• Student not feeling well

• Student has poor grades (failing, retention)

Theory

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

• “The detective has a theory aboutwho robbed the bank.” This is aguess.

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

Theory defined

• An explanation based on manyobservations during repeated

experiments that is valid only if it isconsistent with observations, makespredictions that can be tested, and is

the simplest explanation.• A logical, time tested explanation for

events that occur in nature.

• So the theory of gravity, theory ofelectricity, the germ theory of disease,and the theory of evolution are tested,

accepted explanations for events thatoccur in nature.

• Theories can really never be completelyproven, only disproven. When new evidencecomes along, we must modify our theory orat times even get rid of it and start overagain.

• Ptolemy’s earth centered theory ofthe solar system is an example of

what can happen when new evidencecomes along. When Copernicusshowed that putting the Sun in the

center made it much easier to predictthe planets motions, the old earthcentered theory was discarded and anew one developed.

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.

Graphing Steps

• Identify the Variables

• Determine the range

• Determine the scale

• Number and label each

• Plot the points• Draw the graph

• Give your graph a title

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 datatable.

– Subtract the lowest data value from thehighest data value.

– Do each variable separately.

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

– Spread the graph to use MOST of theavailable space.

Label Axis's

• You need to tell everyone reading your

graph what the graph means.

• Be sure to include units.

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.

Drawing

– Draw a curve or a line that bestfits the data points.

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

• 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

• While your high school teachers might notlike it, I do like putting your name in the

title of the graph.

• Rachel and Max’s Sunspot Graph

Interpolation

• Interpolate:

predicting data

between two measuredpoints on the graph.

Extrapolation

• Extrapolate:

extending the graph,

along the same slope,above or below

measured data.

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 beingmeasured.

How will we measure?

• In the Bouncing Ball Lab

we are measuring how

high the ball bounces

when dropped.

• But where do we measure

• The bottom. Top, or

middle of the ball?

• It makes a difference.

Our Definition

• We will all measure

from the floor to the

bottom of the ball.• This way we will get

consistent results.

scienific method

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