Transcript Identifying Variables

Identifying Variables &
Designing
Investigations
in the Scientific
Method.
Physical Science
3 Kinds of Variables in Physical
Science
 Independent Variable – something
that is changed by the scientist
 What is tested
 What is manipulated
 What is controlled
 Example: Ohm’s law : U = I x R
 Something else?
3 Kinds of Variables in Physical
science
 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
3 Kinds of Variables in Physical
science
 Controlled Variable – a variable that
is not changed
 Also called constants
 Allow for a “fair test”
 Any example we know in Physical
Science?
 What about Newton’ laws?
Let’s look for several examples for Physical Science
First Example we have is
in Physical science:
Wires of different
resistances R were given
the same voltage V in a
closed circuit.
So what is changing?
The current I? Remember
the formula! V = I x R.
Now remember the very
important step in our
investigation!
Let’s identify the variables
in this investigation.
What was the independent
variable?
 resistances of the wires
 Different resistances were
tested by the scientist
 Remember that voltage was
fixed and thus constant!
 So what is changing then?
 Of course, the current!
What was the dependent variable?
 The current!
 The current was observed and
measured by the scientist
 Again the formula of the Ohm’s
law is V = I x R
 V is voltage, I is current, R is
resistance
What was a controlled variable?
 Devices we used to measure:
 Ampermeter
 Voltmeter
 Ohmmeter
 Multimeter
 Something else?
Are you getting the idea?
Or not!?!
Another example in the
Physical Science:
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?
Just be careful!
But give your opinions!?
Go!
Please!
Can we do it!?
Independent variable in
Physical Science:
 Sizes of nails. Why?
 Just because  These were changed by the
scientist. He can pick up
anything he likes!
 Can he?!
Dependent variable:
 Number of paper clips picked
up (by what?) - magnet
 The number of paper clips
observed and counted (by
whom? (measured) (by
whom?)
 What is your answer?
Controlled variables:
 Battery, wire, type of nail
 None of these items were changed
 REMEMBER WHAT IS UNDER CONTROL?
 WHAT ELSE IS NOT CHANGING?
Let’s go to one more
example in Physical
science!
The higher the
temperature of water,
the faster an egg will
boil?!
ARE YOU SURE
ABOUT THAT?
SHALL WE CHECK?
 WHAT WE HAVE IN THIS
INVESTIGATION?
 Let’s see:
 Independent variable – temperature
of water
 Dependent variable – time to cook
an egg
 Controlled variable – type of egg
Last example for today in
Physical Science:
Remember the previous
examples?!
What did you get from
those examples?!
Any idea?!
The temperature of
water was measured at
different depths of a
pond.
 LET’S SUMMARIZE OUR
RESULTS:
 Independent variable – depth of the
water
 Dependent variable – temperature
 Controlled variable – thermometer
THIS IS A VERY IMPORTANT
We are designing Investigations
Basically we plan and do the
steps of work to accomplish our
final goal!
Which was what?!
Now do you see how all is
connected and important?!
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?
 WRITE IT AS A HOMEWORK!
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?
 WRITE IT AS A HOMEWORK !