Scientific Method

• 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.

• 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.

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 did the experiment.

• 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.

Key Idea• When conducting a controlled experiment,

change one factor and keep everything else exactly the same.

• The one thing you change is called the independent variable.

• The resulting change that is being measured is called the dependent variable

• All the things you keep the same are called control variables, or constants.

Galileo’s Experiment

• What was the independent variable in Galileo’s experiment?– 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/ Independent variable: you change this yourself-it’s on its own.

Responding variable/Dependent variable:responds to the change you made-depends on the change you made.

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

can repeat the experiment.

STATEMENT of PROBLEM

• Question that the scientist wants to solve.

• Example: Will it sink or float?

Hypothesis

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

a higher height, then it will bounce higher.

• “If” is the manipulated variable.• “Then” is the responding variable.

HYPOTHESIS• This is the

educated guess that scientist makes about their experiment before they experiment.

Observations• Use one or more of the 5 senses to

gather information• A noting and recording of….

FACTS!!!• Example: There is one TV in the

room.• There are two types of observations.

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• Logical interpretation based upon prior

knowledge and experience• Based upon observations

• Example: When you entered the room, you most likely inferred that the individual in the front of the room is the teacher.

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)

Note the Differences• In laboratory exercises, record

observations NOT inferences

• Inferences may be used when writing the conclusion in your lab report.

• Let’s test your observation skills…

Take a good look at this picture

Question 1

Are there cars parked on the sides of the road?

Question 2

What color is the pickup truck driving in the road?

Question 3

Any minivans around?

Question 4

What does the blue sign say?

Question 5

What's the speed limit?

Question 6

Are there any pedestrians on the road?

Answers

1. Yes

2. Blue

3. Yes

4. Yard Sale

5. 35 mph

6. No

Procedure

• Step by step directions on how to test your experiment.

– Example: 1. Fill up container with

water.2. Gather 10 items to test.3. Test each item one at a

time placing it gently into the water.

Data/Results

• Scientist needs to record data every time they test, then review the data.

• Example: Record if your item floats or sinks.

Conclusion• State whether the

hypothesis was proven correct or incorrect.

• Example: The scientist’s hypothesis was proven correct, the cork floated in the water.

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.

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.