Transcript Chapter 1 - Gordon State College

Chapter 1
The Study of
Chemistry
Topics
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Introduction
Scientific Method
Classifications of Matter
Properties of Matter
Units of Measurement – Metric system
Temperature Conversion
Metric Conversion (Prefixes)
Accuracy vs. Precision
Significant Figures
Density
States of Matter
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Solid
Liquid
Gas
Plasma
ATOM
• Is the simplest unit of matter.
Definitions
• Elements – can’t be decomposed
further into simpler substances
• - 111 elements presently
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- Ds (element 110)
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- Rg (element 111)
• Compound – combination of 2 or
more elements
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Definitions
• Mixtures – combinations of 2 or more
substances (ex. sugar in water)
• 2 Types of Mixtures
• 1. Homogenous Mixtures (solutions) = 1
phase
• 2. Heterogeneous Mixtures = > 2 phases
SOLUTIONS
• Homogeneous mixtures are called
SOLUTIONS.
Solution
• Solution – homogenous
mixture
• A solution is not necessarily a
liquid. Can be gas or solid.
Physical vs. Chemical Properties
• Physical properties – can be measured
w/o changing identity and composition of
substance (ex. Boiling pt.,freezing pt.,
color, odor, density, hardness)
• Chemical properties – describe how
substance reacts or changes to form other
compounds (ex. Flammability, toxicity)
Changes of State and Properties
• Physical changes – does not change
composition of compound
• Chemical changes – converts to a different
chemical substance
• Intensive Properties – independent of amt. (ex.
Density, Temperature, Melting Pt)
• Extensive Properties – dependent on amt. (ex.
Mass, Volume)
Units of Measurement
• Mass – grams; kilogram
• Length – centimeter; meter
• Volume – milliliter or cubic
3
centimeter (cm )
• Temperature – Celcius;
Kelvin
Prefixes in Metric System
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Mega
Kilo
Hecto
Deka
----Deci
Centi
Milli
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million
1,000
100
10
1 (liter, gram, meter)
1/10
or 0.1
1/100 or 0.01
1/1000 or 0.001
Temperature Conversions
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oC
oF
= 273.15 K
= 1.8
oC +
32
Things to Remember!
• 1 milliliter = 1 cc
• 1000 milliliter = 1 liter
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• 0 C = 32 F = 273.15 K
Precision vs Accuracy
• Accuracy – when acquired
value agrees with true value
• Precision – when acquired
values exhibit reproducibility
Significant Figures
• More significant figures =
more certainty
• Helps in determining how
to round measured values
and still precise
SIGNIFICANT FIGURES
• In counting and definitions, there are an
infinite number of sig figs
• In measurements, the number of sig figs
consists of all certain and the first
uncertain digits
• Unit conversions do not determine # of
sig. figs.
Rules of Significant Figures
• 1. Non-zero integers always
count.
• Ex. 1234.5 grams = 5 Sig. Figs.
• 2. Captive zeros are always
significant.
• Ex. 100.3 grams = 4 Sig. Figs.
Rules of Significant Figures
• 3. Leading zeros are NEVER
significant.
• Ex. 0.6780 grams = 4 Sig. Figs.
• 4. Trailing zeroes are significant
ONLY if there is a decimal point
• Ex. 12.0 grams = 3 Sig. Figs
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120 grams = 2 Sig. Figs
Rules of Significant Figures
• 5. Exact numbers (obtained by
counting) are infinite and do not
determine the number of
significant figures.
• Example: 4 cows = ?
Determine the # of Sig. Fig.
• 200.0
• 1050
• 3003
• 0.0006
• 10,000
• 0.5
Rules of Significant Figures
• Multiplication/Division
–Answer will have the same # of
sig figs as the value with the
least # of sig figs
• Ex: 3.8 x 200.0 = 2 Sig. Figs.
Rules of Significant Figures
• Addition/Subtraction
• Answer has the same # of
decimal places as the number
with the least # of decimal places
• Ex. 3.1 + 2.500 + 5.76 = 11.4
Order of Operations
• Parenthesis
• Multiplication/division
• Addition/subtraction
Rounding
• Look only to the right of the number you
are rounding to:
• - If 5 or more, round up
• - If less than 5, round down
General Rule
• Carry ALL figures through to the
end of a problem. Round the final
answer to the correct number of
significant figures
Problem
• Indicate the number of sig. figs. in each of
the following measured quantities:
• A. 358 kg
• B. 0.054 s
• C. 6.3050 cm
• D. 0.0105 L
• E. 7.0500 x 10-3 m3
Problem
• Round each of the following numbers to 4
sig. figs. And express the result in
standard exponential notation.
• A. 102. 53070
• B. 656, 980
• C. 0.008543210
• D. 0.000257870
• E. - 0. 0357202
Problem
• Carry out the following operations and
express the answer with the appropriate
number of sig. figs.
• A. 12.0550 + 9.05
• B. 257.2 – 19.789
• C. (6.21 x 103)(1.1050)
• D. 0.0577 / 0.753
Density
• Is the amount of mass in a unit volume of
the substance
• Is affected by Temperature.
– The higher the temp., the lower the density.
D = mass of substance =
volume of substance
grams
mL or cm3
Density
• Density = mass
volume
= gram
mL
Different ways of calculating volume
• I. For solids with regular shapes:
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For a cube: Vcube = s3
For a rectangular solid, V = L x W x H
For a cylinder: V= pr2h
For a sphere: V = 4/3 pr3
Different ways of calculating volume
• II. For an Irregular Solid
• Water displacement
Different ways of calculating volume
• III. For a liquid
• Use of graduated cylinder, beaker, pipet
or buret.
Problem
• A cube of osmium metal 1.500 cm on a
side has a mass of 76.31 grams at 25 oC.
What is its density in g/cm3 at this
temperature?
Problem
• The density of titanium metal is 4.51
g/cm3 at 25 oC. What mass of titanium
displaces 65.8 mL of water at 25 oC?
Problem
• The density of benzene at 15 oC is 0.8787
g/mL. Calculate the mass of 0.1500 L of
benzene at this temperature.