The Scientific Method

August 2008

Mrs. Sinclair

6th Grade Science

“One test is worth a thousand expert opinions.” ~Bill Nye

What is the Scientific Method?

• A series of steps that scientist use to answer questions and solve problems.

• Goal: To come up with reliable answers and solutions.

A Little History

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

Aristotle was very influential. In other words, Aristotle was so famous that his work influenced thinking in the Western world from his time to the present. Aristotle and his contemporaries believed that all problems could be solved by simply thinking about them.

Sometimes this worked, other times it did not. For example, Aristotle thought that heavy objects would fall faster than lighter ones. This was fine when he was right. But he was so influential that his mistakes were never noticed.

Problem with Aristotle’s Thinking?

• 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.

Who is 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!

How Their Ideas Merged

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.

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

Key Ideas/ Factors to Think About…

• 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.

What was the 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.

Kinds of VariablesIndependent Variables

Independent Variables- a variable that changes unrelated to other factors; a variable we manipulate, or change, on purpose.

An independent variable is the variable whose value we know before we start an experiment. (independent variable value we know)

Example: Does the drop height affect the bounce height of a superball? We know the drop heights we will use.

Dependent Variables

• A dependent variable is a variable that changes depending on some other factors; the variable we are trying to find

• The dependent variable is the variable whose value we do not know before we start an

• Example: Does the drop height affect the bounce height of a superball?

• We do not know the bounce heights before we start.

Constant

• A constant is a variable that does not change for the duration of an experiment; a value that remains the same.

• Example: Does the drop height affect the bounce height of a superball?

• The superball does not change during the experiment.

6 Steps of the Scientific Method

1. Ask a Question

2. Form a Hypothesis

3. Test the Hypothesis

4. Analyze the Results

5. Draw Conclusions

6. Communicate results

Step 1

• Ask a Question.

• Good questions come from careful observations. Use your senses! These questions drive the scientific method.

Step 2

• Form a Hypothesis

A hypothesis statement is a statement that expresses the expected answer to the

problem statement…• –what you think the results of the

experiment will show.• •Example: If a superball is dropped from

increasing heights then the bounce heights will also increase because …

Step 3

• Test the Hypothesis

• Keep in mind the variables and constants.

Step 4

• Analyze the Results• After you have completed your

experiments, made your observations, and collected your data, you must analyze all of the information you have gathered.

• Tables and graphs are often used in this step to organize your data.

Step 5

• Draw Conclusions.• Based on the analysis of your data,

you should conclude whether or not your results supported your hypothesis.

• You may have to check for errors, repeat experiment for verification, reject your hypothesis, or experiment further. This is science!

Step 6

• Communicate Results

• After any scientific investigation, you should report your results. By doing a written or oral report, you let others know what you have learned.

Think Like a Scientist!

How do I do This?

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.

Observations

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

Qualitative• Qualitative observation:

(quality) Usually made with our senses.

• Color, shape, feel, taste, sound.• Ex: The dog is wearing a blue

sweater.• The desktop 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 and prior knowledge.

• What does this mean in 6th grade terms?

Making Inferences• You are at the counter in the

office to get your teacher’s mail. 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? Family problems at home (sick, accident)?Student not feeling well?Student did not want to come to school today?

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.

More on Theory

• So the theory of gravity, theory of electricity, or the germ theory of disease 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.

Theory Example

• 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.

• You are a scientist in the making!