Transcript The Scientific Method

The Scientific Method
Movie
An experiment tests an idea in a
careful orderly manner. The
orderly steps used are called
The Scientific Method.
Stating the Problem
• A scientific question
that can be answered
by gathering evidence.
Example:
Which freezes
faster, fresh water
of salt water?
Research
Gathering information on the problem.
Develop a Hypothesis
• A hypothesis is a
prediction about the
outcome of the
experiment. A
properly worded
hypothesis should take
the form of an If
…then… statement.
Example:
If I add salt to
fresh water, then
the water will
take longer to
freeze.
Designing an Experiment
• Next, you need to develop
a plan to test your
hypothesis. Your plan
should describe the
observations or
measurements you will
make.
• In a well designed
experiment, you need to
keep all variables the same
except for one.
•
•
•
•
A variable is any factor that can
change in an experiment.
The factor that you change is
called the manipulated
variable or independent
variable.
The responding variable or
dependent variable is what you
measure or observe to obtain
your results.
A controlled variable is a
factor that is kept constant. You
use the control to make a
comparison.
Example of an
Experimental Procedure
Fill 3 containers with
•
300 milliliters of cold tap
water.
2. Add 10 grams of salt to
•
container 1 and stir.
Add 20 grams of salt to
container 2 and stir.
•
Add no salt to container
3.
3. Place the 3 containers in a
freezer.
•
4. Check the containers every
15 minutes. Record your
observations.
1.
The manipulated/independent
variable is the amount of salt added
to the water.
The responding/dependent
variable is how long it takes the
water to freeze.
The control is container 3, which has
no salt added. This allows you to
compare how long it takes regular
water and salt water to freeze.
Notice that the other factors, such as
the amount of water or starting
temperature are kept constant. This
ensures valid results and that only
one variable is tested.
Hypothesis: an educated guess or prediction;
an “if, then” statement
If ……..independent variable,
then…..dependent variable.
Example:
Independent Variable:
I feed my cat a lot of food
Dependent Variable
she will get fat
If ___________________________
then _________________________
Remember
Try to use INCREASE and DECREASE
in your hypothesis!
Ex. IF I increase the amount of food I give
my cat, THEN she will increase her weight
Now Try it on Your Own!
‘Writing a Good Hypothesis”
Just ‘plug and chug’ in your variables!
Types of Variables
There are 2 main types of variables:
Independent Variable: The variable that is changed
by the scientist; the ‘I control’ variable
Dependent Variable: The variable that might change
because of what the scientist changes – what is
being measured
Remember!
Your hypothesis can TELL you what your
variables are!
Ex. If I drink Mountain Dew before bed, then
I will not sleep very much.
IV: Drinking Mountain Dew
DV: the amount of sleep
Practice
Use this hypothesis to identify the variables:
If I leave all the lights on all day,
then my electric bill will be
Expensive.
IV: ______________________
DV: ______________________
If I brush my cat more, then there will be less
fur on my furniture
IV: ______________________
DV: ______________________
Now read the following experiment and identify the
independent and dependent variables
Elizabeth wanted to test if temperature affected how fast milk
goes bad and curdles. She left milk in a room temperature
closet, a fridge, and a oven that was turned on low heat.
She then measured how rotten the milk was after 10 days.
IV: ____________________________________
DV: ____________________________________
Operational Definition
Before beginning the experiment, you must have a
clear operational definition. An operational
definition is a statement that describes how a
particular variable is to be measured or how a term
is to be defined.
For example, how will you determine if the water
is frozen? You might decide to insert a stick in
each container in the beginning of the
experiment . Your operational definition of
frozen could be the time at which the stick can
no longer move.
Review
In an experiment, there is something that a
scientist is testing – they control this…
Review
In an experiment, because the scientist is
changing this independent variable, this is
going to change and the scientist will
measure that change…
Review
This is an educated guess of what is going to
happen during an experiment – the scientist
forms this at the beginning of the
experiment….
Did You Get Them Right?
1. Independent Variable
2. Dependent Variable
3. Hypothesis
Constant
Constant: something that
scientist makes sure is the
same throughout the
experiment.
Ex. Watering the plants the
same amount of water or
making sure you are testing
the same person every time.
Control
Control: The part of the
experiment that the scientist
doesn’t change or add the
variable to.
Ex. The plant with the white
light.
Materials
•
Before beginning the
experiment, make a
list of all the
materials you will
need to complete it.
Observations
You perform the experiment & see what
happens. You may need to take
measurements, pictures etc. depending on
the nature of the experiment.
Observation
• What is an observation?
– Using your five senses to take note of and
observe your surroundings
• Let’s go over examples!
Inference
• An inference is when you make an
assumption or prediction about something
that you observe
• After you make an observation, you usually
make an inference about what is going on
Let’s practice making inferences!
The next three slides show some fossil imprints that
were found during a archeological dig. We’re
going to record some observations and then make
some inferences about what may have happened
millions of years ago….
What do you think happened?
Data
• The observations &
measurements you make
in an experiment are
called data. You gather
that data and organize it
into tables, charts or
graphs. Then think
through what the data
reveals. Does it support
your hypothesis?
Types of Data
• Quantitative Data:
Involves
measurements or
numbers. This data is
organized into graphs
(bar, line, etc.)
• Qualitative Data:
Involves descriptions
or words. This data is
organized into tables
or pictures.
Axes of a Graph:
• X-axis (horizontal axis)
Horizontal means:
• Y-axis (vertical axis)
Vertical means:
Label the x and y axes
35
30
25
20
15
10
5
0
Label the x and y axes
35
Y-Axis 30
Dependent
25
Variable
20
15
10
5
0
X-Axis (Independent Variable)
Scale
Now you need to select evenly spaced intervals
that include all your data (a scale).
Data set 1: 15, 30, 45, 7, 64. 96
Minimum value for scale:____
Maximum Value for scale:____
Intervals
Now you need to select evenly spaced intervals
that include all your data (a scale).
Data set 1: 15, 30, 45, 7, 64. 96
Minimum value for scale:__7_
Maximum Value for scale:_96_
Title:_____________________
500
400
Money
300
200
100
0
10
20
30
Student Number
40
50
Title:_____________________
500
Money
400
300
200
100
0
10
20
30
40
Student Number
50
Remember TAILS
• T – Title
• A – Axis (Draw the X & Y Axis)
• I – Intervals (Pick an interval for your
data numbers)
• L – Label each axis
• S – Scale should take up a page or
half a page (never tiny).
Drawing a Conclusion
• A conclusion is a
statement that sums up
what you have learned
from an experiment. You
need to decide whether the
data you collected
supports your hypothesis
or not. You should repeat
an experiment several
times before you can draw
any conclusions from it.
Repeating the Work
• Before the conclusion of can be accepted by
the scientific community, other scientists
must repeat the experiment & check the
results.
• So when a scientist writes a report, it must
be detailed enough so that scientists around
the world can repeat the experiment for
themselves.
Find Flaws in this Experiment.
• Gerard wants to find out if egg yolk causes silver
to tarnish. He labels 2 silver spoons A & B. He
puts egg yolk on both spoons. Then he places
spoon A in a closed container and leaves spoon B
out in the open air. He checks the spoons over the
next few days.
• Flaws: Egg yolk, which is suppose to be the
variable, should not be put on both spoons.
Other factors, such as the exposure to air,
should be kept the same for both spoons.
Find Flaws in this Experiment.
• Daria wants to find out if fertilizer causes plants
to grow taller. She takes 2 plant shoots of the
same size & type and labels them A & B. She adds
fertilizer to plant A but not to plant B. Then she
places plant A in a sunny window and waters it
everyday. She places plant B on a bookshelf away
from the sun and waters it every other day.
• Flaws: The experiment has too many variables.
Daria has varied the amount of light and water
each plant receives. Except for fertilizer, all
other conditions should be kept the same.
Problem Solving
• Hypothesis: Turtle eggs develop into male
turtles in cold temperatures and into
female turtles in warm temperatures.
• Predict whether this hypothesis is fact or
fiction. Design a simple experiment to
show if the hypothesis is or is not correct.
Make sure your experiment has an
experimental setup and a control setup.
Practice Drawing a Conclusion
• Here is one way a biologist might design the
experiment. A great quantity of the same type of
turtle eggs are collected. Batches of 25 eggs are
out in containers at different temperatures.
After 60 days, the following data is recorded:
Temp.
26°C
28°C
30°C
32°C
Male
21
13
1
1
Female
2
11
19
20