Transcript Scientific Method

Essential Question
Why do we trust that scientists have correct
explanations for how ‘things’ work?
Observations
Scientists use observations during an
investigation to gauge how the process is going
but they also make many observations to design
their investigations.
How do we make observations?
Are some observations more important than
others?
Steps in the Scientific
Method
Observation
Hypothesis
Experiment
Data Collection
Conclusion
Retest
Observations
Gathered through your
senses
A scientist notices
something in their
natural world
Experiment
A procedure to test the
hypothesis.
Experiment
Variable – factor in the
experiment that is being
tested.
Experiment
A good or “valid”
experiment will only have
ONE variable!
Scientific Experiments
Follow Rules
An experimenter
changes one factor and
observes or measures
what happens.
The Control Variable
The experimenter makes a special effort to keep
other factors constant so that they will not affect
the outcome.
Those factors are called control variables
What is the purpose of a
control?
Controls are NOT being tested
Controls are used for COMPARISION
Other Variables
The factor that is changed is known as the
independent variable.
The factor that is measured or observed is
called the dependent variable.
Examples of Controls and
Variables
For example, suppose you want to figure out the
fastest route to walk home from school.
You will try several different routes and time how
long it takes you to get home by each one.
Since you are only interested in finding a route
that is fastest for you, you will do the walking
yourself.
What are the variables in
your experiment?
Varying the route is the independent variable
The time it takes is the dependent variable
Keeping the same walker throughout makes the
walker a control variable
One more thing… it is best to make several trials
with each independent variable.
Remember: To be a Valid
Experiment:
Two groups are required – the control &
experimental groups
There should be only one variable
Hypothesis
A suggested solution to
the problem..
Must be testable
Sometimes written as
If… Then… statements
Predicts an outcome
Hypothesis
An example of a
hypothesis might be that
the salamanders have
curved tails due to a
pollutant in the moist soil
where they live.
Rules in Constructing a
Hypothesis
Do not use I, me, my, they – no possessive pronouns.
If possible needs to be in an independent –
dependent variable format. (IF this happens, THEN
this will happen.)
It is a statement, not a question
Example:
If salt is added to fresh water, then the water will take
longer to freeze.
The If statement explains how the manipulated
variable is going to be changed.
The then statement explains how the responding
variable is affected by changing the manipulated
variable.
If the mass of a paper helicopter is increased, the
the time it takes to drop to the ground will decrease.
If fertilizer is given to a plant, then the growth of the
plant will increase
If a ball is hit with a wooden bat, then the ball will
travel farther than an aluminum bat.
What is Wrong
Hypothesis 1: If plants are given fertilizer, then the height of the plant will
change
In hypothesis 1 the then statement is not specific enough
Hypothesis 2: If a plant’s height increases, then it was because of the
fertilizer
In hypothesis 2 the dependent variable was talked about in the if statement
and the independent variable was talked about in the the statement.
Hypothesis 3: If the height of the plant that is given fertilizer increases,
then it is because the fertilizer gave the plant added nutrients.
Hypothesis 3 has two problems. The first problem is like hypothesis 2, the
if and then statements are mixed up. The second problem is this
hypothesis does not give a prediction for the scientific question stated
above. It gives a prediction on why fertilizers make plants grow more.
Practice 1
Amy wants to see how the amount of water in a pot
affects the time that it takes for water to reach
boiling point. She boils 100, 200, 300 ml of water. The
time it takes for the water to reach boiling point
increases as the amount of water increases.
List the independent variable, dependent variable,
and the needed controls
Construct a possible Hypothesis
Answer to Practice 1
Independent: Amount of Water
Dependent: Boiling Time
Controls: Type of water, heating apparatus
Constructing a Hypothesis:
If water amounts increase, then the time needed for water to
reach the boiling point will also increase.
Practice 2
A study was done to see if leaves added to soil had an effect on
tomato production. Tomato plants were grown in four large tubs.
Each tub had the same kind and amount of soil. The 1st tub had
15 kg of rotted leaves mixed in the soil and 2nd had 10 kg. The 3rd
tub had 5 kg and 4th tub had no leaves added. Each tub was kept
in the sun and watered the same amount. The number of
kilograms of tomatoes produced in each tub were recorded
What is the independent variable? Dependent variable?
What are the controls?
Write a possible hypothesis for this experiment.
Answers to Practice 2
Independent: Amount of Leaves
Dependent: Kilograms of tomatoes produced
Controls: Soil type and amount, Sun and water amount.
Hypothesis:
The larger amount of leaves added to soil will produce
larger amounts of tomatoes.
It is hypothesized that changing the amount of
decomposing leaves in soil will not effect tomato growth.
Practice 3
James wondered if music had an effect on plant growth. He set
up an experiment where 25 bean plants were placed in a
chamber where music was played and 25 bean plants were
placed in an identical chamber where music was not played. The
growth chambers were kept at the same temp and all plants
received the same amount of sunlight, fertilizer, and water. At the
end of 2 weeks plant height was measured.
What is the purpose?
What is the independent variable? Dependent variable?
Write a possible hypothesis for this experiment
Answers to Practice 3
Independent Variable: Music being played
Dependent Variable: Growth of plant
Hypothesis:
If music is played to plant over a period of time, then the growth of the
plant will increase.
If music is played to plant over a period of time, then the growth of the
plant will decrease.
If music is played to plant over a period of time, then the growth of the
plant will have no effect
Data
Results of the
experiment
May be quantitative or
qualitative
Data
Must be organized
Can be organized into
charts, tables, or graphs
Data – observations and measurements
made during an investigation
Qualitative Data – describes the situation and reaction in descriptive
terms. For example, qualitative involves the senses including sight,
taste, hearing, touch, and smell. This would include color and shape
Quantitative – includes those things that can be measured (length,
time, mass, temp. etc.)
Qualitative vs. Quantitative Data –
http://www.regentsprep.org/Regents/math/ALGEBRA/AD1/qualquant.htm
http://regentsprep.org/regents/math/algebra/ad1/dataprac.htm
Do we need both?
A well-designed investigation must have some
type of MEASURABLE data, quantitative, but
qualitative gives the measurable data more
description and accuracy.
Scientists use qualitative data to record
observations that are difficult to measure or to
give clarification to measured data.
Conclusion
The answer to the
hypothesis based on the
data obtained from the
experiment
Retest
In order to verify the
results, experiments
must be retested.
Solving a Problem
Identify a problem
State Observations about the
problem
Form a Hypothesis about the
problem (if… then…)
Design an Experiment to test the
hypothesis
Collect Data
Form a Conclusion
Retest
Let’s Review
The Scientific Method
A team of scientists wonder if the amount of Vitamin A given to laboratory
white mice would affect the number of offspring born. An experiment is set
up using the same species of white mice. Each mouse in the study gets the
same amount of food, daily exercise, and is kept at the same temperature.
Once group of mice gets extra vitamin A supplements added to their food. The
number of offspring are counted and recorded.
Which of the following is the best Hypothesis – Explain why the wrong ones are incorrect.
1.
Mice will have more offspring if they are given Vitamin A.
2.
If the mice are exposed to Vitamin A, then the amount of offspring will increase.
3.
If you give mice Vitamin A, then they will have more offspring
4.
I think the offspring number will increase if the mice are exposed to Vitamin A.
On Your Own
A scientist wonders how acid might effect salamander’s hatching
and growth. A scientist places 100 salamander eggs (Group X) in a
pond that is exposed to acid rain. He places another 100 eggs
(Group Y) in a pond where acid rain has not been detected. The
conditions such as temperature, mineral content of the water,
amount of sunlight are as similar as possible in both areas.
1.
Determine Independent Variable? (2pts each)
2.
What are some possible Dependent variables?
3.
Construct an Hypothesis for this experiment.
On Your Own
Candy wondered if caffeine would affect the breathing rate of
goldfish. She went to the store and purchased 10 goldfish of
approximately the same age and size, identical containers, food, and
caffeine tablets. In one container she placed 5 goldfish with no
caffeine. In the other container she placed 5 goldfish with caffeine
tablets dissolved in the water. She observed the goldfish behavior
and counted the operculum (plate that covers gills) movements in
both containers of fish.
1.
Determine Independent Variable?
2.
What are some possible Dependent variables?
3.
Construct an Hypothesis for this experiment.