Chapter Two Notes - Warren County Schools

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Transcript Chapter Two Notes - Warren County Schools

Chapter 2 Outline
Data Analysis
And Measurement
I. The Metric System
A. U.S. only industrial
country in world not to
use as primary system
B. Used in all sciences as
system of measurement
C. Uses base units - and
prefixes - that are easily
manipulated
D. Base Units
1) Length
2) Volume
Meter - the length of a
meter stick
Liter - the amount of
liquid that will fill a
container that is one
decimeter cubed.
1 dm^3 = 1 liter
1 cm^3 = 1 milliliter
3) mass - kilogram which is about equal to 2 lbs
(1kg = 2.2 lbs) - grams are often used in
chemistry 454 grams = 1 pound.
E. Prefixes
• kids
kilo (k)
larger
• have
hecta (h)
• died
decka (dk)
• over [ grams, liters,meters,seconds]
• doing
deca (d)
• conversions
centi (c)
• metric
milli (m)
smaller
F. Metric to Metric Conversions
The factor label method
1) Underline what is to be solved for
2) Write down what is given
3) Make a conversion factor (C.F.) with the
units of the given on the bottom
4) The units to solve for go on top
5) Use the prefix chart to determine which unit is
larger - it receives a value of one
6) Use the chart to count how many units of ten to
assign to the smaller unit
7) Multiply across by the top and divide by the
bottom to obtain answer.
8) Be sure to include units on your answer
9) Example problems
1) How many grams are there in 400 cg?
2) How many ml are in 2 dkl?
3) How may km are in 40,000 dm?
4) How many cg are in 24 dg?
II. Metric to English
and Special Conversions
A. English to Metric Conversion Factors &
other C.F.s. 1 yard = 36 in , 1ft = 12in
454 g = 1 pound
1 L = 1dm^3
2.54cm = 1 inch
1 ml = 1cm^3
2,000 pounds = 1 ton 1 meter = 1.09 yrd
60 sec = 1 min
1 kilometer = 0.62 miles
60 min = 1 hr
1 mile = 5280 feet
Practice Problems
1) How many cm are in 2 feet ? (60.96)
2) How many meters are in a 100 yard football
field? (91.4)
3) Convert 4 lbs to mg? ( 1.82x10^6)
4) How many cubic meters are in a room
measuring 8ft x 10ft x 12ft? (27.2)
5) How many ml are in a box that measures 2.2 by
4 by 6 in? (865cm^3 = 865ml)
6) How many kilometers are in 143.56 yards?
7) A car is traveling 9.06 km per hour. How many
meters per minute is it traveling?
(151)
8) Convert 40 miles/hr to meters/sec.(17.92)
III. Significant Figures
Scientists must record their
data in a way that tells the
reader how precise her
measurements are.
Therefore, the rules of
significant figures must be
observed.
A. The precision of the instrument used to measure
determines whether a figure is known or
estimated. What is the value given to the bar
below. How many significant figures are there?
1 2 3 4 5 6 7 8 9 10 11 12 13
10.5?
Is the .5 in 10.5 significant?
Yes. It is an estimate and
therefore significant.
Estimates are often called
doubtful figures.
B. Significant figure rules.
1. All non-zero numbers are significant.
Example 3.45 = 3 s.f. 3.556 = 4 s.f.
2. Zeros at the end of a number that include a
decimal point are significant
Example 3.40 = 3 s.f. 0.500 = 3 s.f.
3. Zeros between significant figures are significant.
Example 3.02 = 3 s.f.
3.04032 = 6 s.f.
4. Zeros just for spacing are not significant.
Example 0.000345 = 3 s.f. 3.45 x 10^-4
If a number is listed as 7000g there is just one
s.f. Use scientific notation to list 4 s.f.
7.000 x 10^3g
5. Counting numbers and exact numbers have an
infinite number of significant numbers.
Example 40 cars or 1000 mm = 1 m
Practice Problems
• Identify the number of significant figures:
1) 3.0800
2) 0.00418
3) 7.09 x 10¯5
4) 91,600
5) 0.003005
6) 3.200 x 109
7) 250
8) 780,000,000
9) 0.0101
10) 0.00800
Answers
1)5 2)3 3)3 4)3 5)4 6)4 7)2 8)2 9)3 10)3
D.Calculations With Significant
Figures
1. Multiplication and Division
• The following rule applies for multiplication and
division:
• The LEAST number of significant figures in any
number of the problem determines the number of
significant figures in the answer.
• Example #1: 2.5 x 3.42.
• The answer to this problem would be 8.6 (which
was rounded from the calculator reading of 8.55).
Why?
• 2.5 has two significant figures while 3.42 has
three. Two significant figures is less precise than
three, so the answer has two significant figures.
• Example #2: How many significant figures will the
answer to 3.10 x 4.520 have?
• You may have said two. This is too few. A
common error is for the student to look at a
number like 3.10 and think it has two significant
figures. The zero in the hundedth's place is not
recognized as significant when, in fact, it is. 3.10
has three significant figures.
2. Addition and Subtraction
• 1) Count the number of significant figures in the
decimal portion of each number in the problem.
(The digits to the left of the decimal place are not
used to determine the number of decimal places
in the final answer.)
• 2) Add or subtract in the normal fashion.
• 3) Round the answer to the LEAST number of
places in the decimal portion of any number in
the problem.
• WARNING: the rules for add/subtract are different
from multiply/divide. A very common student error
is to swap the two sets of rules. Another common
error is to use just one rule for both types of
operations.
Practice Problems
1) 3.461728 + 14.91 + 0.980001 + 5.2631
2) 23.1 + 4.77 + 125.39 + 3.581
3) 22.101 - 0.9307
4) 0.04216 - 0.0004134
5) 564,321 - 264,321
Answers
1. 24.61
2. 156.8
3. 21.170
4. 0.04175
5. 300,000 correct 3.00000 x 105
The Structure of the Atom
History, Structure, Properties and Forces
Early Theories of Matter
I. Before the early 1800’s
many Greek philosophers
thought that matter was
formed of air, earth, fire
and water.
II. Democratus
A. First to propose atomos
- matters as small
indivisible particles
B. Said they move through
empty space
C. different properties of
matter due to changes in
arrangement of atoms