Transcript What variable is being changed?

Today is Tues., Oct. 1st
Please take a Scientific Packet & your clicker
Take out your binder & open to Table of Contents
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What is Science?
A. Definition
1. Science is investigating and understanding the
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natural world
2. It is the ability to explain events in the natural world
3. It is the ability to use those explanations to make
useful predictions
B. Science deals only with the natural world
C. Scientists
1. collect and organize information in a careful, orderly way, looking
for patterns and connections between events
2. Scientists propose explanations that can be tested by examining
evidence
3. Science is an organized way of using evidence to learn about the
natural world
D. Goal
1. To understand the laws to give explanations for events that occur
2. Aims to use the explanations to find & understand patterns
3. Aims to use the explanations to make useful predictions about
natural events
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Scientific Method
The scientific method is:
A series of steps used by scientists to
solve a problem or answer a question.
The Steps to the Scientific Method
1. Observation / Asking a Question
2. Form a Hypothesis
3. Design a Controlled Experiment
4. Record and Analyze Results
5. Draw Conclusions
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How is Science Done?
B. Process
1. Observation
a. Process of noticing and describing events in a careful,
organized way
b. Leads to questions and inferences
2. Hypothesis
a. possible explanation for a set of observations or a
possible answer to a scientific question
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What is a hypothesis?
1. A guess
2. A joke
3. An educated
guess
4. A fact
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Step 1:
Observation / Asking a
Question
A problem or a question
must first be identified.
Step 2: Form a Hypothesis
Hypothesis
A possible explanation
to the question or
problem.
It is simply a prediction and has
not yet been proven or disproven.
How much water can a root
hair absorb?
Why does a plant stem bend
toward the light?
What effect does
temperature have on heart
rate?
It must be stated in a
way that is testable.
A statement is
considered “testable”
if evidence can be
collected that either
does or does not
support it.
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Which is NOT true about the
observation step?
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1. It’s unorganized
2. It’s a process of
noticing events
3. It leads to questions
4. It leads to
inferences
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How is Science Done?
3. Experiment
a. Once a hypothesis is made one must test it using controls and variables
b. Controlled experiment
1. An experiment in which only one variable is changed
2. Done to be able to see what causes the change
c. Independent variable
1. The variable that is changed
d. Dependent variable
1. The variable that is observed and changed because of the
modifications of the independent
e. Control group
1. Group in the experiment that is exposed to the same
condition as he experiment group except for one
independent variable
**** test must have a large sample to get a
true picture of results of the experiment
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4. Collect & Analyze data
a. The information collected when doing an experiment
b. The data that has been collected must be organized and
analyzed to determine whether the data are reliable
c. Two types
1. Qualitative data
a. descriptions and involve characteristics that cannot be
counted
2. Quantitative data
a. numbers and are obtained by counting or measuring.
d. Does the data support or not support the hypothesis
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What’s the importance of a
control in the experiment?
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1. To confuse others
2. To show change
3. To show what
happens
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What’s the independent variable?
1. Something
observed
2. Something that is
changed
3. Something added
to confuse others
4. Something to
throw off the
experiment
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What is the dependent variable?
1. Something added
to confuse others
2. Something
observed
3. Something to
throw off the
experiment
4. Something that is
changed
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5. Drawing a conclusion
a. The evidence from the experiment is used to determine if the
hypothesis is supported or not supported, change
the hypothesis or to draw a valid conclusion
b.
Experiments must be repeated over and over. When repeated, the
results should always be the same before a valid
conclusion can be reached.
c. Theory
1. A theory may be formed after the hypothesis has been tested
many times and is supported by much evidence.
2. A broad and comprehensive statement of what is thought to be
true.
3. A theory is supported by considerable evidence.
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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 control group.
Even though the volunteers are given
identical looking pills, the control group will
not actually receive the vaccine.
Describe the experimental group.
This group will receive the vaccine.
What variables are kept constant?
The size, shape, color, and texture of
the pill.
What variable is being changed?
Whether or not the pill contains the
vaccine.
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There are two variables in an experiment:
a) The independent
variable is the
variable that is
deliberately
changed by the
scientist.
b) The dependent variable is the
one observed during the
experiment. The dependent
variable is the data we collect
during the experiment. This
data is collected as a result of
changing the independent
variable.
c) In the above
example, what is the
independent
variable?
It is the addition of the
vaccine to the pills
that were given to the
volunteers.
d) In the above
example, what is
the dependent
variable?
The observed
health of the people
receiving the pills.
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You want to determine the effects
of a certain fertilizer on the
growth of orchids grown in a
greenhouse. Materials that are
available to you include:
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.
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How will you set up a controlled experiment?
Here is one possibility:
The 100 plants will be
divided into 4 groups as follows:
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.
The plants will be
watered daily.
Over a period of a
month, the plants
will be measured
to see which ones
grew the tallest.
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Control Group
What is the control
group in this
experiment?
The control group
consists of the 25 plants
that are receiving plain
water.
Experimental Group
What is the experimental
group in this experiment?
The experimental group
consists of the 75 plants
that are receiving various
concentrations of
fertilizer.
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In a “controlled 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
fluid 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.
What variable is being changed in this experiment?
The variable being changed is the amount of fertilizer
received by each group of plants.
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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 orchids would grow
best with a medium concentration of fertilizer.
The results do not support this.
The results disprove our hypothesis.
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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.
What is your conclusion based on these
results?
 Orchids grow best with a weak
concentration of fertilizer.
 At medium to high concentrations, plant
growth is inhibited.
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Analysis Questions
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
gives validity to the test
results.
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Analysis Questions
Why is it so important that a scientist
accurately describes the procedure
used in the experiment?
It allows other scientists to
repeat the experiment and verify
the results.
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When doing a controlled experiment, why
must all the variables but one be kept
constant throughout the experiment?
1. So there’s no
confusion
2. To know which
variable is
responsible for the
results
3. Neither of the above
4. Both A & B
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What is a theory?
1. A fact
2. Statement of what
is believed to be
true
3. A hypothesis
4. An education
guess
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The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people on the Dutch East Indies.
The disease was beriberi. Symptoms of the disease included weakness and loss
of appetite, victims often died of heart failure. Scientists thought the disease might
be might be cause by bacteria, They injected chickens with bacteria from the blood
of patients with beriberi. The injected chickens became sick, however, so did a
group of chickens that were not injected with bacteria.
One of the scientists, Dr. Eijkman, noticed something. Before the experiment all
the chickens had eaten whole-grain rice, but during the experiment, the chickens
were fed polished rice. Dr. Eijkman researched this interesting case and found out
the polished rice lacked thiamine, a vitamin necessary for good health.
1. State the problem
What causes BeriBeri
2. What was the hypothesis?
Caused by bacteria
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3. How was the hypothesis tested?
Injected the bacteria from the blood of infected people into
the chickens
4. Should the hypothesis be supported or rejected on the experiment?
rejected
5. What should be the new hypothesis and how would you test it?
Caused by the lack of thiamine
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6. Identify the problem
How is mold killing bacteria?
7. What was Flemming’s hypothesis?
Thought mold produces a substance that kills the bacteria
8. How was the hypothesis tested?
Took the mold to the nutrient broth; next removed the mold then
finally put broth on bacteria
9. Should the hypothesis be supported or rejected on the experiment?
support
10. This experiment led to the development of what major medical
advancement?
penicillin
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Different rose bushes are grown in a greenhouse for two month. The number
of flowers on each bush are counted at the end of the experiment.
IV -
DV -
Type of rush bush
Number of flowers
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You water three sunflower plants with salt water. Each plant receives a different
concentration of salt solution. A fourth plant receives pure water. After a two week
period, the height is measured.
IV --
DV --
CG --
Concentration of salt water
height
Pure water
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