Unit 1 Part 2: Measurement MR. GATES CHEMISTRY. Measurement Measurement is a quantitative...
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Unit 1 Part 2: Measurement MR. GATES CHEMISTRY. Measurement Measurement is a quantitative description of both a number and a unit. Ex. 6 feet and 2 inches
Measurement Measurement is a quantitative description of both a
number and a unit. Ex. 6 feet and 2 inches
Slide 3
Standards There needs to be standards in order for units to
work. The Kings foot.
Slide 4
Accuracy vs. Precision Accuracy describes how close a
measurement is to the accepted value Precision describes how close
a measurement is to other measurements taken.
Slide 5
Percent Error
Slide 6
Significant Figures All numbers in a measurement that can be
known precisely plus one additional number that is estimated.
Digits in a measurement that indicate the precision of an
instrument used to take a measurement.
Slide 7
Examples (going for a walk) 3 miles (3 estimated) 1.9 miles (9
estimated) 1.91 miles (1 estimated) 1.918 miles (8 estimated)
Slide 8
Which Figures are Significant? All nonzero digits are
significant Ex. 5.3 has two significant figures Zeroes appearing in
front (to the left) of a nonzero digit are NOT significant Ex.
0.0275 has three significant figures Zeroes appearing in between
two nonzero digits are ALWAYS significant Ex. 2.054 has four
significant figures Zeroes appearing to the right of a nonzero
number and after the decimal place are significant. Ex. 32.810 has
five significant figures Zeroes to the right of nonzero digits and
to the left of a decimal place are ambiguous. Ex. 300 has ?? it
depends
Slide 9
Ambiguous Numbers??? 200 miles 200. miles 200.0 miles
Slide 10
Practice How many significant figures are in the following
numbers? a).0891 b)109.3 c)6.0 d)0.0005 e)1.089 f)7.0020
g).08340
Slide 11
Rules for Rounding If the number to the right of the last
significant figure is from 0-4, round down. If the number to the
right of the last significant figure is from 5-9, round up.
Examples: 26.819 rounded to three significant figures is 26.8
Rounded to four significant figures is 26.82 Practice: 0.01037
Rounded to three significant figures? Rounded to two significant
figures?
Slide 12
Practice Round the number 34.1050 to: a)2 sig figs a)34 b)5 sig
figs a)34.105 c)4 sig figs a)34.11 d)3 sig figs a)34.1 Round the
number 0.0539801 to: a)2 sig figs a)0.054 b)5 sig figs a)0.053980
c)4 sig figs a)0.05398 d)3 sig figs a)0.0540
Slide 13
Exceptions that Make the Rule There is an UNLIMITED amount of
sig figs in two circumstances. Counted numbers 23 students in class
(cant have a fraction of a person) Exact/defined quantities 12
inches in a foot Like
12.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000 (catching my
breath)000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000.
To infinity and beyond zeroes
Slide 14
Sig Figs w/ Calculations Addition or Subtraction The answer can
have no more decimal places than the number with the least decimal
places in the calculation. Ex. 4.56-1.2= 3.36, but with proper sig
figs the answer is =3.4 Ex. 9.64+1.751= 11.391, but with proper sig
figs the answer is = 11.39
Slide 15
Sig Figs w/ Calculations Multiplication and Division The answer
can have no more sig figs than the number with the least amount of
sig figs in the calculation. Ex. 1.24 x 2.6 = 3.224, but with
proper sig figs the answer is... = 3.2 Ex. 5.11 x 6.551 = 33.47561,
but with proper sig figs the answer is = 33.5
Slide 16
Scientific Notation Scientific notation is a number written as
the product of two numbers. Follows the following format: M x 10 N
M is some number between 1 and 10 N is the amount of times the
decimal places had to be moved. N decimals
Slide 17
Putting #s in Sci. Notation Every time the decimal place is
moved the exponent must move too. M x 10 N If the decimal moves
then the exponent goes down If the decimal moves then the exponent
goes up
Slide 18
In and Out Put into scientific notation: 0.0000361
9,840,000,000 Take out of scientific notation: 3.65 x 10 7 2.49 x
10 -4
Slide 19
Sig Figs and Sci. Notation All of the numbers in proper
scientific notation are significant No ambiguous numbers!!! 2000 is
2.00 x 10 3 with three sig figs.
Slide 20
Addition/Subtraction in Sci. Notation Adding and Subtracting:
Exponents must be the same!!! EX:5.1 x 10 5 + 6.07 x 10 5 11.17 x
10 5 (not correct sig figs) 11.2 x 10 5 (not correct sci not.) 1.12
x 10 6
Slide 21
Multiplying/Dividing in Sci. Notation Multiplying and Dividing:
EX: 7.2 x 10 2 x 4.2 x 10 3 30.24 x 10 5 (not correct sig figs) 30.
x 10 5 (not correct sci. not.) 3.0 x 10 6
Slide 22
International System of Measurement Internationally used system
of measurement known as the Metric System
Slide 23
Benefits of Using the Metric System Scientist all over the
world use this system. They can share and understand each others
work. Based on multiples of ten. Makes for easier conversions.
Slide 24
SI Base units
Slide 25
Volume The amount of space an object takes up. Base unit is cm
3
Slide 26
Mass The amount of matter in an object. Base unit is the kg
because the gram is too small.
Slide 27
Weight The pull gravity has on the mass of an object.
Slide 28
Fluid Volume When dealing with a fluid (gas or liquid) the most
commonly used unit is the liter (L) 1ml = 1cm 3
Slide 29
SI Prefixes
Slide 30
Dimensional Analysis Method of converting from one unit to
another of equal value using conversion factors.
Slide 31
Conversion Factors
Slide 32
Using Dimensional Analysis 1.32kg1000g1000mg 1kg1g
Slide 33
Converting Complex Units What is 19 in 2 in ft 2 ?