Topic: Scientific Method
Aim: Explain how a controlled experiment is
performed.
Do Now: Variables reading (ISNB)
HW: Castle Learning due Wednesday.
(Directions are under the Helpful Resources section
of my website)
Observations and Inferences reading due
tomorrow!
Lab safety quiz on Wednesday.
www.castlelearning.com
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Does fertilizer X help plant
growth?
• 2 groups:
Parts of a
controlled 1.Experimental
group:
contains
the
experiment
independent
VARIABLE
2.Control group:
DOES NOT contain
the independent
variable
Control Group
Experimental
Group
2 types of 1. Independent
variables
Variable:
the 1 factor that’s
different between
experimental and
control groups
Independent variable = ?
SUNLIGHT
2. Dependent Variable =
what is MEASURED (data)
HEIGHT
Height = 12 cm
Height = 21 cm
How do we make
the results of
an experiment
more
reliable/valid/
accurate?
• Repeat
experiment
• Use a larger
sample size
Let’s summarize…
1. Explain the difference between the
control and experimental groups.
2. Explain the difference between the
independent and dependent
variables.
3. How can the results of an
experiment be more accurate?
Experiment
1. What is the independent variable?
2.What is the dependent variable?
3.Explain the difference between the
control group and experimental groups
in this experiment.
An investigation was done with an
electromagnetic system made from a
battery and wire wrapped around a nail.
Different sizes of nails were used. The
number of paper clips the electromagnet
could pick up was measured.
Independent variable:
• Sizes of nails
• These were changed by the
scientist
Dependent variable:
• Number of paper clips picked
up
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Which statement is true about the
experimental group (s) in an
experiment?
a. It does not contain the independent
variable.
b. It contains 2 variables.
c. It contains the independent variable.
d. It is exactly the same as the control group.
Review:
To investigate how temperature affects seed
germination, a student placed 10 radish seeds of
the same variety on moist paper in each of 3 petri
dishes and placed the dishes in the following
environments:
Dish # 1: Refrigerator, 5ºC
Dish # 2: Room Temperature, 20ºC
Dish # 3: Incubator, 37ºC
1. Which factor is the variable in this
investigation?
a. temperature
b. kind of seeds
c. moisture
d. number of seeds
To investigate how temperature affects seed germination, a student
placed 10 radish seeds of the same variety on moist paper in
each of 3 petri dishes and placed the dishes in the following
environments:
Dish # 1: Refrigerator, 5ºC
Dish # 2: Room Temperature, 20ºC
Dish # 3: Incubator, 37ºC
2. The control group is
a. Dish #1
b. Dish #2
c. Dish #3
3. The dependent variable is the
a. temperature
b. how many days till germination
c. The # of seeds
d. the amount of water
What is the factor in an experiment that
remains constant?
a. control
b. variable
c. theory
d. hypothesis
6. The results of one experiment carried out by
a research team would be considered valid
if
a. the experiment had no control setup
b. all the members of the research team came to
the same conclusion
c. the experiment had more than one variable
d. the experiment was repeated and the same
results were obtained each time
An investigation was done with an
electromagnetic system made from a
battery and wire wrapped around a nail.
Different sizes of nails were used. The
number of paper clips the electromagnet
could pick up was measured.
Independent variable:
• Sizes of nails
• These were changed by the
scientist
Dependent variable:
• Number of paper clips picked
up
The higher the
temperature of water,
the faster an egg will
boil.
• Independent variable?
• temperature of water
• Dependent variable?
• time to cook an egg
Beta-carotene supplements have been thought to
protect against cancer. A study was conducted
with 39,000 women aged 45 and up. Group A
received a beta-carotene supplement. Group B
received a placebo. Their health was studied
over their lifetime. Cancer rates for women
taking the beta-carotene supplement did not
really differ from the cancer rates of those
women taking the placebo.
Identify the independent variable, dependent
variable, control group, and experimental
group.
Ex # 2: To investigate the effect of a substance on plant
growth, 2 bean plants of the same species were grown
under identical conditions with Substance Z added to the
soil of one of the plants. At the end of 2 weeks, the plant
grown with Substance Z was 12.5 cm tall. The plant
grown without Substance Z was 12.2cm tall. The
researcher concluded that the presence of Substance Z
causes the plants to grow taller.
What is the independent variable?
Substance Z
What is the dependent variable? height
Which setup is the control?
Plant without Substance Z
Ex #3: A student placed 5 geranium plants
of equal size in 5 environmental chambers.
Growing conditions were the same for each
plant except for the amount of water each
received. At the end of 20 days, the width of
the leaves was measured.
What is the independent variable?
What is the dependent variable?
Which setup is the experimental group?
5. An investigation was designed to determine
the effect of ultraviolet light on mold spore
growth. Two groups of mold spores were
grown under identical conditions, except
one group was exposed only to ultraviolet
light, while the other group was grown in
total darkness. In this investigation, the
group of mold spores grown without
receiving any ultraviolet light is known as
the
a. experimental variable
b. hypothesis
c. control
d. limiting factor
Watch the video about lab safety rules.
http://www.youtube.com/watch?v=tsAHt0
FiwNM&feature=related
Review:
The first step in the scientific
method is
a. to state the problem
b. experimentation
c. to state the hypothesis
d. observation
An educated guess to the
problem of an experiment is
known as a
a. variable
b. theory
c. hypothesis
d. law
When performing an
experiment, you are testing
the
a. problem
b. hypothesis
c. data
d. conclusion
Your senses can be used to make
a(n)
a. observation
b. conclusion
c. hypothesis
d. problem