Transcript Identifying Variables - Mrs. Church6th Grade Science

Identifying Variables
Kinds of Variables
 Independent Variable – something
that is changed by the scientist
 What is tested
 What is manipulated
 Changed on purpose to see what may
happen
Kinds of Variables
 Dependent Variable – something that
might be affected by the change in
the independent variable
 What is observed
 What is measured
 The data collected during the
investigation
Kinds of Variables
 Controlled Variable – a variable that
is not changed
 Also called constants
 Allow for a “fair test”
The Bread Experiment
 Let’s discuss variables, constants and
controls using the bread experiment!
Problem/Question
John watches his
grandmother bake
bread. He asks his
grandmother what
makes the bread rise.
She explains that yeast
releases a gas as it
feeds on sugar.
Problem/Question
John wonders if the
amount of sugar used
in the recipe will affect
the size of the bread
loaf?
Hypothesis
The hypothesis is an educated
guess about the relationship
between the independent and
dependent variables.
Note: These variables will be
defined in the next few slides.
Do you know the difference
between the independent and
dependent variables?
Independent Variable
The independent, or
manipulated variable, is a
factor that’s intentionally varied
by the experimenter.
John is going to use 25g., 50g.,
100g., 250g., 500g. of sugar in
his experiment.
Dependent Variable
The dependent, or responding
variable, is the factor that may
change as a result of changes
made in the independent
variable.
In this case, it would be the size
of the loaf of bread.
Control Group
In a scientific experiment, the
control is the group that serves
as the standard of comparison.
The control group may be a “no
treatment" or an “experimenter
selected” group.
Control Group
The control group is exposed to
the same conditions as the
experimental group, except for
the variable being tested.
All experiments should have a
control group.
Control Group
Because his grandmother
always used 50g. of sugar in
her recipe, John is going to use
that amount in his control
group.
Constants
John has to keep all
other factors the same
so that any observed
changes in the bread
can be attributed to
the variation in the
amount of sugar.
Constants
The constants in an
experiment are all the
factors that the
experimenter attempts
to keep the same.
Can you think of some
constants for this
experiment?
Constants
They might include:
Other ingredients to the
bread recipe, oven used,
rise time, brand of
ingredients, cooking time,
type of pan used, air
temperature and humidity
where the bread was
rising, oven temperature,
age of the yeast…
Another Example:
Students of different ages
were given the same jigsaw
puzzle to put together.
They were timed to see how
long it took to finish the
puzzle.
Identify the variables in
this investigation.
What was the independent
variable?
 Ages of the students
 Different ages were tested by
the scientist
What was the dependent variable?
 The time it to put the puzzle
together
 The time was observed and
measured by the scientist
What was a controlled variable?
 Same puzzle
 All of the participants were
tested with the same puzzle.
 It would not have been a fair
test if some had an easy 30
piece puzzle and some had a
harder 500 piece puzzle.
Yet Another example:
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.
What are the variables in this
investigation?
Independent variable:
 Sizes of nails
 These were changed by the
scientist
Dependent variable:
 Number of paper clips picked
up
 The number of paper clips
observed and counted
(measured)
Controlled variables:
 Battery, wire, type of nail
 None of these items were changed
Guess what?
One more:
The higher the
temperature of water,
the faster an egg will
boil.
 Independent variable – temperature
of water
 Dependent variable – time to cook
an egg
 Controlled variable – type of egg and
amount of water
Last one:
(I promise)
The temperature of
water was measured at
different depths of a
pond.
 Independent variable – depth of the
water
 Dependent variable – temperature
 Controlled variable – thermometer
and pond
Designing Investigations
The greater the amount of soap in a
soap and water mixture, the bigger a
soap bubble can be blown.
 Design an investigation to test this
hypothesis.
 Identify the variables
 What exactly will be changed? How
will it be changed?
 What exactly will be measured? How
will it be measured?
Variables
 Independent
Variable- soap
 Dependent
Variable- size of
bubble blown
 Controlled
Variable-water and
type of soap
 Amount of soap in
water mixture
 Size of the bubble
blown with different
amounts of soap in
the water
The farther a ball drops, the higher
it will bounce.
 Design an investigation to test this
hypothesis.
 Identify the variables
 What exactly will be changed?
How will it be changed?
 What exactly will be measured?
How will it be measured?
Variables
 Independent
 The length of the
Variable- length of
fall
 Dependent
Variable-height of
bounce
 Controlled
Variable- ball,
surface, size of the
ball
fall, different fall for
each trial
 The height of the
bounce from the
different lengths of
the fall ~ the higher
the height of the
fall the higher the
bounce