Science and the

scientific methodMr. Banks

7th and 8TH grade science

What is science?

Science is the study of the

structure and behavior of the

physical and natural universe, to

find explanations to why and

how things occur.

What is science?

Scientists collect and

organize information. They

look for patterns and

connections within the

information they gather.

Scientists then propose

explanations that can be

tested by examining

evidence.

Observations and data

Science begins with an observation about the

universe.

Plants grow differently based on how much they

are watered.

Different metals conduct electricity differently.

Observations and data

An observation is the

process of gathering

information, or data,

about something.

Data is the information

gathered from making

observations.

Data

There are two types of data.

Quantitative data are observations

that can be measured or counted.

Ex. There are a certain number of

males and females in this class.

Qualitative data are observations

that are descriptions or cannot be

counted.

Ex. The softness of a cat’s fur.

Hypothesis

A Hypothesis is a testable scientific

explanation for a set of observations.

The explanation must be testable to

be a hypothesis.

The scientific method

Scientists follow a set of guidelines when

investigating natural occurrences.

The scientific method is a procedure for

asking and answering scientific questions

by making observations and doing

experiments.

It is a cycle where questions are asked,

information is gathered, and new

questions are asked.

The scientific method

1. Make an observation

2. Research

3. Create a hypothesis

4. Design an experiment

5. Gather and analyze data

6. Draw conclusions

7. Share results

8. Modify and repeat?

1. Make an observation

Identify a question or problem you or others

have observed.

How much water can a plant’s roots absorb?

Why does a plant stem bend toward the light?

What effect does temperature have on heart

rate?

2. Research

Find out if others have asked this question

and find out what they found.

Look online, in books, and in scientific

journals.

3. Create a hypothesis

After considering the

information out there

now, create a possible

explanation to the

question.

This is just a prediction

and must be tested.

4. Design an experiment

A hypothesis must be tested.

An experiment is a procedure designed to

create a situation in which data can be

gathered to support or refute a hypothesis.

We’ll talk about how to design an

experiment later.

5. Gather and analyze data

Data created by an experiment

must be recorded and analyzed to

determine if they are reliable and

what they mean.

6. Draw conclusions

What information did we

learn?

Has the hypothesis been

supported or did the

experiment indicate the

hypothesis might be

wrong?

Do we need to conduct a

new experiment?

7. Share the information

Tell others, usually in written form, so when

they do research about their own

observations, they will have your information

to help them.

Science builds over time.

If I have seen further it is by standing on the shoulders of Giants.

-Sir Isaac Newton

8. Modify and repeat?

Do I need to repeat my experiment to learn

more?

Do I need to do a different experiment to

gather more evidence?

Usually, yes. Science is basically never finished.

Grog the ancient farmer

1. Make an observation

2. Research

3. Create a hypothesis

4. Design an experiment

5. Gather and analyze

data

6. Draw conclusions

7. Share results

8. Modify and repeat?

Designing an experiment

Scientific ideas must be tested by

experimentation and gathering data.

Scientific experiments must be designed in a

deliberate way.

Enough data must be gathered to learn

something, but having too much in an

experiment can make the results confusing.

Variables

Variables are factors of an experiment that can change.

Ex. Temperature, amount of light, time, concentration of chemicals, or species of animal.

Some variables the scientist will changes, but others change on their own.

In a well designed experiment, the scientist only changes one variable at a time.

If multiple variables are changed at once, you might have trouble figuring out which one is effecting your results.

Variables

There are two types of variables.

The independent variable is the variable that

is directly changed by the scientist.

Remember, scientists usually only change ONE

variable at a time.

Variables

There are two types of variables.

The dependent variable(s) are the changes

observed during the experiment.

This is the data collected during the experiment.

Dependent variables change as a result of

changing the independent variable.

Grog the ancient farmer

What would be the

independent and

dependent variables

in Grog’s experiment?

Today you will need your

interactive notebook, a glue stick,

and a pair of scissors. Get these

after you do your journal.

Variables

Within an experiment there are two groups; the

control and the experimental.

The two groups are identical except for one

factor.

The independent variable.

The experimental group is the group in which

the independent variable has been changed.

Variables

The control is the “normal group” in an

experiment where everything, including the

variable being tested, is kept at what is

considered “normal”.

This group’s purpose is to serve as a comparison for

the experimental group.

Example

In order to test the effectiveness of a new vaccine, 50

volunteers are selected and divided into two groups.

One group will be the control group and the other will

be the experimental group. Both groups are given a pill

to take that is identical in size, shape, color and texture.

Describe the experimental group.

Describe the control group.

What variables are kept constant?

What variable is being changed?

This group will receive the vaccine.

Even though they are given identical

looking pills, they will not actually receive

the vaccine.

The size, shape, color, and texture of

the pill.

Whether or not the pill contains the

vaccine.

Practice Problem:

You want to determine the effects of a certain fertilizer on the growth of tomatoes grown in a greenhouse. Materials that are available to you include: a greenhouse, 100 orchid plants, water, fertilizer, and soil. You want to know if the orchids will grow best with a weak concentration of fertilizer, a medium concentration of fertilizer, or a high concentration of fertilizer. How will you design an experiment to test different concentrations of this fertilizer?

State your hypothesis:

Possible answer:

I predict that the

orchids will grow best

with a medium

concentration of

fertilizer.

How will you set up an experiment?

The 100 plants will be divided into 4

groups as follows:

The plants will be

watered daily.

Over a period of a

month, the plants

will be measured

to see which ones

grew the tallest.

Group 1: 25 plants will receive plain

water.

Group 2: 25 plants will receive a weak

concentration of fertilizer.

Group 3: 25 plants will receive a

medium concentration of fertilizer.

Group 4: 25 plants will receive a high

concentration of fertilizer.

Control Group Experimental Group

What is the control

group in this

experiment?

The control group

consists of the 25 plants

that are receiving plain

water. What is the experimental

group in this experiment?

The experimental group

consists of the 75 plants

that are receiving various

concentrations of

fertilizer.

In a good experiment, all variables must be kept

constant except the one variable that is being

changed.

What variables must be kept

constant in this experiment?

All plants must receive the same amount of

water/fertilizer each day.

All plants are grown in pots of equal size.

All plants are grown at the same temperature.

All plants receive the same amount of sunlight.

All plants are the same species.

What variable is being changed in this experiment?

The variable being changed is the amount of

fertilizer received by each group of plants.

Group 1 (Control Group): Grew to an average height of 15 cm.

Group 2 (Weak conc.): Grew to an average height of 35 cm.

Group 3 (Medium conc.): Grew to an average height of 28 cm.

Group 4 (High conc.): Grew to an average height of 10 cm.

Is your hypothesis supported or disproved

by these results?

We hypothesized that the corn would grow

best with a medium concentration of

fertilizer.

The results do not support our hypothesis.

After one month of measuring the corn,

the following data is obtained:

Titling an experiment

Scientific studies have simple, straight forward titles that often follow this format.

The effect(s) of (the independent variable) on(the dependent variable.

For example:

The effect of different amounts of fertilizer on the height of corn plants.

The title may be boring, but it is very informative.

Writing a hypothesis

Hypotheses also generally

follow a format in order to

convey a lot of information.

If (the independent variable)

is (increased, decreased,

changed), then (the

dependent variable) will

(increase, decrease, change).

For example

If the amount of fertilizer is

increased, then the height of

the corn will increase.

Question

Why is it important to have a large

sample size in any experiment?

If the sample size is too small, an inaccurate conclusion

may be reached.

Ex. An accident occurs and the one control plant dies. Now

we don’t have anything to compare our experimental plants

to.

Vs.

Why is it important to repeat the

experiment many times?

Experiments should be repeated to see if the

same results are obtained each time. This

makes the results more believable.

Question

+ +

What is the importance of the control?

The control shows what

will happen under normal

circumstances. Without

the control, there is

nothing to compare your

results to and no way to

know how your

independent variable

effected your experiment.

Question

On page 7 of your interactive notebook, I

want you to come up with and create a

picture that demonstrates the relationship

between a pair of independent and dependent

variables. Similar to the one below.