Transcript Math in Science ppt

Mrs. Ebener’s Review of
DOING MATH IN SCIENCE..
(1) Scientific Notation
A short-hand way of writing
large numbers without
writing all of the zeros.
Step 1 & 2
Move decimal left
Leave only one number in front of
decimal & then
Write number without zeros
= 9.3
Step 3
Count how many places you moved
decimal
Make that your power of ten
The power of ten is 7 because the
decimal moved 7 places.
93,000,000 --Standard Form
9.3 x 107 --Scientific Notation
Form
Practice Problems
Write in scientific notation.
1) 98,500,000 = 9.85 x 10?
2) 64,100,000,000 = 6.41 x 10?
3) .000279 = 2.79 X 10?
4) .0042 = 4.2 x 10?
More Practice Problems
.
1) 734,000,000 =
2) 870,000,000,000 =
3) 90,000,000,000 =
4) 50,000 =
5) .0000072 =
6) 802,000,000,000 =
Scientific Notation to
Standard Form
Move the decimal to the right
3.4 x 105 in scientific notation
3.40000 --- move the decimal
340,000 in standard form
Write in Standard Form
1. 6.27 x 106
2. 9.01 x 104
3. 6.2
X 10 4
4. 8.5 X 10 3
(2) Significant Figures
Sig Figs
Those digits in a final calculation that
have physical meaning
Determined by the accuracy of the
measurement
Remember this:
All nonzeros ARE significant.
But with the zero……
Beginning is Never.
Middle is Always.
End is Yes Dot,
No Dot No!
Ex: 000505000
Sig Fig Practice
.00452
05600
600
709
006.
9.0100
0.390
(3) TRY to Just G U E S S
when solving word problems
G…..Record the GIVEN information.
U…...Identify the UNKNOWNS of the
problem.
E…...Decide the EQUATION to use.
S…..SHOW your work.
S…..SOLVE and circle your answer.
Find the density:
Density equals mass divided by volume.
Problem: An unidentified metal has a volume
of 15.4 cm3 and a mass of 109.34 grams.
What’s the density of the metal?
(4) Dimensional Analysis

a method of doing algebra with units

Uses known relationships to determine
unknown relationships

Allows to get rid of units – cancel them out
to – to get answers in wanted units.

Also called other things like factor labeling,
Conversion Factor Method or Unit Analysis
Practice:
A) 1 kg = ____ g
D) 7.44 km = __ in
(1 km=.62 mi )
B) 7.7 km = ___ mm
E) A sphere with the mass
C) 82 days= ___ h
of 100 mg would most likely
be the mass of ____.
A) an English pea
B) a baseball
C) Cinderella’s carriage
Dim Anal Big Bad Bonus
A lab took 20 min + 45 s + 3 days to
complete. How long was this in
hours?
 You
have to get all numbers in
same unit before you can do the
math.
 First one with answer (to nearest
.01 place in complete decimal form)
(5) Estimate
Are there any special skills needed?
ESTIMATION
Does you answer even make any sense??
You should be able to THINK METRIC !
(6) Precision VS Accuracy
PRECISION
The degree of exactness
of a measurement
How well the number of
independent
measurements agree with
each other
“Reliable” – or repeatable
or getting the same
measurement each time
ACCURACY
How close to the true
value a given
measurement is
How well the results of
the measurement agree
with the real value
“Correct” – it reflects the
size of the thing being
measured
CITED
SOURCE FOR TARGET GRAPHIC
http://celebrating200years.noaa.gov/magazine/tct/accuracy_vs_pre
cision.html
http://www.fordhamprep.org/gcurran/sho/sho/worksheets/worksht2
8a.htm
(7) Percent Error
A measure of how accurate your
measurement is
How accurate your experiment really is
Formula:
Measured value-Predicted
value/Predicted value X 100
(Your answer can be negative if the answer is less than the true
value.)
Practice Percent Error
calculations
A student takes an
object with an accepted
mass of 200.00 grams
and masses it on his
own balance. He
records the mass of the
object as 196.5
g. What is his percent
error?
Working in the
laboratory, a student
find the density of a
piece of pure aluminum
to be 2.85 g/cm3. The
accepted value for the
density of aluminum is
2.699 g/cm3. What is
the student's percent
error?
(7) And Always Follow PEMDAS
((from left to right across the equation))
1) P (Parenthesis & other Grouping symbols) - solve
inside grouping symbols first; grouping symbols include
(), {}, [], //
2) E (Exponents & Fraction Bars) – always set
superscripts above integers; Ex: 10²
3) M & D (Multiply & Divide) - in the order of
appearance- from left to right
4) A & S (Add & Subtract) - in the order of appearance
-from left to right
Example from
www.purplemath.com
Simplify 16 – 3(8 – 3)2 ÷ 5. (I must
remember to simplify inside the
parentheses before I square, because
(8 – 3)2 is not the same as 82 – 32.)
Simplify 7 X 4 / 8 + 72 – 1
(That’s a fraction bar!!)
And what if my mean teacher gives me a
variable that’s not what the equation says to
solve for????
v=d / t
D=m/v
1. What’s the mass of a rectangular object with the
dimensions 3 cm x 2 cm x 5 cm & a density of
3.2 g/cm3 ?
2. Alexandra runs 12.42 meters per second. How
far has she run in 22.5 seconds? Do you
estimate this to be pretty fast for a teenager or
not?
Could you convert any of the above to another
unit?? Try!!