Scientific Method

I Can Statements

At the end of this lesson, you should be

able to say, with confidence:

• I can describe six basic steps in the scientific

method that can be used for investigations.

• I can explain how to run a controlled experiment.

• I can distinguish between an independent variable,

a dependent variable, and a controlled variable.

• I can determine which type of graph would best

display various forms of data.

The scientific method consists of a set of steps that can

be used to investigate observations in nature.

Scientific Method

A student watched a video of Mentos candy being

placed in a 2 Liter bottle of Diet Coke and

wondered if they could make a larger explosion.

Make Observations

Scientists and other curious

people often observe something

happening and begin to wonder

why its happening or if it can be

done differently.

The first step in the scientific method, is to make

observations.

The second step is to form a hypothesis.

Form an Hypothesis

If the temperature of the Diet Coke is changed, the

explosion will be larger.

In order to be useful, a

hypothesis must be

able to be tested.

A hypothesis is usually

framed as an ‘if… then’

statement.

The third step is to test the hypothesis by

performing an experiment.

Perform Experiment

Experiments test the effect of one variable on another

variable using controlled conditions.

Experimental Process

In an experiment, anything that can be changed,

or can vary, is called a variable.

TemperatureHeight of

Explosion

Type &

Amount of

Soft Drink

Type &

Amount of

Candy

Procedure

Controlled Experiment

TemperatureHeight of

Explosion

Type &

Amount of

Soft Drink

Type &

Amount of

Candy

Procedure

In a controlled experiment, all the variables must be kept

the same except the variable that is being tested.

Since the student is testing the effects of temperature

on the explosion, everything else needs to be kept

exactly the same.

In a controlled experiment, all the variables must be kept

the same except the variable that is being tested.

Controlled Variables

The type and amount of Diet Coke, the type and amount of

Mentos candy, and the procedure used are all controlled

variables, in the student’s experiment.

Independent VariableThe variable being tested or changed during each

experimental trial, is called the independent variable.

In this case, temperature is the independent variable.

The dependent variable is the variable that is

measured during the experiment.

Dependent Variable

The results of the

dependent variable will

depend upon the

independent variable.

In this case, the height of the explosion is the

dependent variable.

A control group is an experimental set up in which no

variable is changed, not even the independent variable.

Control Group

Control

Group

Warm Temperature

Room Temperature

Cold Temperature

Since the student is testing temperature, the control

group would contain a Diet Coke in which the

temperature was not changed. (Room Temperature)

The fourth step is to gather and analyze the data, or the

information, collected during an experiment.

Gather and Analyze Data

Temperature Height (cm)

Cold ?

Room Temperature ?

Hot ?

In order to keep the data organized, the

student is going to use a data table to record

the measurements.

Line Graphs Bar Graphs

Circle Graphs

In order to easily analyze the data, graphs are often

used to visually represent the data.

There are three types of basic graphs:

Analyze the Data

Line graphs show the relationship between the

independent and dependent variables over time.

The dependent

variable is always

placed on the Y axis

and time is placed

on the X axis.

Line Graphs

Bar graphs are used for comparing measured

quantities.

Bar Graphs

Randolph County students who have read Tom Sawyer.

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mb

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f S

tud

ents

Girls Boys

WHS ER Trinity SW

Circle graphs or pie charts are used for comparing

percentages.

School30%

Sleeping30%

Recreation30%

Studying10%

A Day in the Life of a Teenager

Circle Graphs

Analyze the Data

0

10

20

30

40

50

60

70

80

Cold Room Temperature Hot

He

igh

t (c

m)

Temperature

Diet Coke and Mentos Explosion

In Diet Coke and Mentos experiment, the height of

each explosion is being compared, so a bar graph

would be used.

The independent

variable,

temperature, is

placed on the X axis.

The dependent

variable, height, is

placed on the Y axis.

The fifth step is to draw a conclusion by deciding if the

hypothesis was supported or not supported, based on

the facts you gathered.

Draw a Conclusion

0

10

20

30

40

50

60

70

80

Cold Room Temperature Hot

He

igh

t (c

m)

Temperature

Diet Coke and Mentos Explosion

If the Diet Coke

is heated , the

explosion will

be larger.

Hypothesis

Hypothesis was

supported

If the hypothesis is not supported, then the hypothesis

can be revised or the hypothesis may just be rejected.

Unsupported hypotheses are still helpful because they tell us what doesn’t happen.

“We have not failed, we have found over 1,000

ways how not to build a light bulb”

Thomas Edison’s encouraging words to

an assistant.

Hypothesis Not Supported

Other QuestionsOne innate trait of a scientist or people who enjoy

science, is curiosity.

A lot of times,

after an

experiment has

been performed,

other questions

may arise.

Now that you know how to test a hypothesis, you

can answer all of the other questions by running

further experiments.

?

RetestIn the scientific community, when a hypothesis is

supported, other scientist would also run the

same experiment.

If after many retests,

the hypothesis was

always supported,

then the hypothesis

can become a theory.

In science, a theory is an explanation for how

something works, in nature, that is supported by a

large body of evidence.

The End