What type of Measurement are made in Chemistry? 1.Qualitative
Measurements Descriptive, non-numerical formDescriptive,
non-numerical form Color, shape, size, feelings, textureColor,
shape, size, feelings, textureExample: The basketball is round and
brown. 2.Quantitative Measurements Definite form with numbers AND
unitsDefinite form with numbers AND units Mass, volume,
temperature, etc.Mass, volume, temperature, etc.Example: The
basketball has a diameter of 31 cm and a pressure of 12 lbs/in
2.
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In science, we deal with some very LARGE numbers: 1 mole =
602000000000000000000000 In science, we deal with some very SMALL
numbers: Mass of an electron = 0.000000000000000000000000000000091
kg Scientific Notation
Slide 5
Imagine the difficulty of calculating the mass of 1 mole of
electrons! 0.000000000000000000000000000000091 kg x
602000000000000000000000 x 602000000000000000000000
???????????????????????????????????
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Scientific Notation: A method of representing very large or
very small numbers in the form: M x 10 n M x 10 n M is a number
between 1 and 10 n is an integer # of times to move the decimal If
n is negative, the number is really small If n is positive, the
number is really large.
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2 500 000 000 Step #1: Insert an understood decimal point. Step
#2: Decide where the decimal must end up so that one number is to
its left up so that one number is to its left Step #3: Count how
many places you bounce the decimal point the decimal point 1234567
8 9 Step #4: Re-write in the form M x 10 n
Slide 8
2.5 x 10 9 The exponent is the number of places we moved the
decimal. Since it was a large number, the exponent is
positive.
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0.0000579 Step #2: Decide where the decimal must end up so that
one number is to its left up so that one number is to its left Step
#3: Count how many places you bounce the decimal point the decimal
point Step #4: Re-write in the form M x 10 n 12345
Slide 10
5.79 x 10 -5 The exponent is negative because the number we
started with was less than 1.
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PERFORMING CALCULATIONS IN SCIENTIFIC NOTATION ADDITION AND
SUBTRACTION
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4 x 10 6 + 3 x 10 6 IF the exponents are the same: 1. add or
subtract the numbers in front 2. bring the exponent down unchanged.
7 x 10 6
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4 x 10 6 - 3 x 10 6 The same holds true for subtraction in
scientific notation. 1 x 10 6
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4 x 10 6 + 3 x 10 5 If the exponents are NOT the same, we must
move a decimal to make them the same.
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4.00 x 10 6 + 3.00 x 10 5 Student A 40.0 x 10 5 43.00 x 10 5 Is
this good scientific notation? NO! = 4.300 x 10 6 To avoid this
problem, move the decimal on the smaller number!
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4.00 x 10 6 + 3.00 x 10 5 Student B.30 x 10 6 4.30 x 10 6 Is
this good scientific notation? YES!
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A Problem for you 2.37 x 10 -6 + 3.48 x 10 -4
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2.37 x 10 -6 + 3.48 x 10 -4 Solution 002.37 x 10 -6 0.0237 x 10
-4 3.5037 x 10 -4
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PERFORMING CALCULATIONS IN SCIENTIFIC NOTATION MULTIPLICATION
AND DIVISION
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4 x 10 6 x 3 x 10 6 IF the problem is multiplication: 1.
Multiply the numbers as usual 2. add the exponent. 12 x 10 12
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24 x 10 9 3 x 10 6 IF the problem is division: 1. Divide the
numbers as usual 2. subtract the exponents: numerator - denominator
8 x 10 3
Slide 22
Calculate the following answer: 0.000 000 000 000 000 000 000
000 000 000 91 kg 0.000 000 000 000 000 000 000 000 000 000 91 kg
______ x 602 000 000 000 000 000 000 000
??????????????????????????????????? 9.1 x 10 -31 x 6.02 x 10 23
54.782 x 10 -8 5.4782 x 10 -7 kg
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Practice Problems #1 1. 5.7 x 10 6 + 3 x 10 5 2. 3.8 x 10 5 -
2.1 x 10 6 3. 1.35 x 10 7 + 8 x 10 5 4. 8.52 x 10 -9 + 2.16 x 10
-9
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Practice Problems #2 5. 7 x 10 6 / 2 x 10 4 6. 5 x 10 8 x 5 x
10 3 7. 5 x 10 3 / 2 x 10 3 8. 2 x 10 7 x 4 x 10 -9
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Precision and Accuracy Accuracy refers to the agreement of a
particular value with the true value. Precision refers to the
degree of agreement among several measurements made in the same
manner. Neither accurate nor precise Precise but not accurate
Precise AND accurate
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Percent Error Accepted Value Correct value based on reliable
references. Example: Boiling Point of water is 100C Experimental
Value Value measure in lab. Example: Boiling Point measured in lab
reads 99.1C Percent Error = x 100 | experimental value accepted
value | accepted value |99.1 100| 100 100 x 100 0.9 0.9 100 100 x
100 = 0.9% error Errors less than 5-10% is acceptable!
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International System of Units (SI)
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The Fundamental SI Units (le Systme International, SI)
QuantitySI Base UnitSymbolOther Symbols Lengthmeterm Volumecubic
meterm3m3 liter (L) Masskilogramkm Density grams / cubic centimeter
g/cm 3 grams / milliliter (g/mL) TemperaturekelvinKdegree Celcius
(C) Timeseconds PressurepascalPaatmosphere (atm)
EnergyjouleJcalorie (cal) Amt of Subs.molemol
Units of Length UnitSymbolRelationshipExample Kilometerkm1 km =
10 3 mLength of 5 city blocks Metermbase unitHeight of door knob
Decimeterdm10 1 dm = 1 mDiameter of orange Centimetercm10 2 cm = 1
mWidth of button Millimetermm10 3 mm = 1 mThickness of dime
Micrometermm10 6 m = 1 mDiameter of a bacteria Nanometernm10 9 nm =
1 mThickness of an RNA
Slide 31
Units of Volume UnitSymbolRelationshipExample LiterLbase
unitQuart of Milk MillitermL10 3 mL = 1 L20 drops of water Cubic
Centimeter cm 3 1 cm 3 = 1 mLcube of sugar MicroliterLL10 6 L = 1
Lcrystal of table salt
Slide 32
Units of Mass UnitSymbolRelationshipExample Kilogramkg base
unit 1 kg = 10 3 g small textbook Gramg1 g = 10 -3 kgdollar bill
Milligrammg10 3 mg = 1 gten grains of salt Microgramgg10 6 g = 1 g
particle of baking powder