Transcript Chapter 1

Chapter 1
Chemistry: The Study of Matter
What is Chemistry?
The study of matter, its composition,
properties, and the changes it undergoes
Applied Chemistry is the using of chemistry to
attain certain goals, in fields like medicine,
agriculture, and manufacturing
Pure Chemistry gathers knowledge for
knowledge sake
Branches of Chemistry
Analytical Chemistry -studies composition of
substances.
Organic Chemistry -compounds containing
carbon
Inorganic Chemistry -substances without
carbon
Biochemistry- Chemistry of living things
Physical Chemistry studies behavior of
substances


rates and mechanisms of reactions
energy transfers
Chemistry is
A natural science
A language with its own vocabulary
A way of thinking
Scientific Method
A way of solving problems or answering
questions
Starts with observation- noting and
recording facts
Hypothesis- an educated guess as to
the cause of the problem or answer to
the question
Scientific Method
Experiment- designed to test the
hypothesis
Only two possible answers
1) hypothesis is right
2) hypothesis is wrong
Generates data observations from
experiments
Modify hypothesis- repeat the cycle
Variables
Controlled experiment- Only want one
thing to change at a time in a laboratory.
Manipulated variable- What you change
or control directly
Also called independent variable
Responding variable – What changes
as a result. No direct control
Also called dependent variable
Observations
Hypothesis
Theory
(Model)
Modify
Experiment
Prediction
Law
Experiment
Observations
Hypothesis
Experiment
Cycle repeats many
times.
The hypothesis gets
more and more
certain.
Becomes a theory
A thoroughly tested
model that explains
why things behave a
certain way.
Observations
Hypothesis
Experiment
Theory can never
be proven.
Useful because
they predict
behavior
Help us form mental
pictures of
processes (models)
Observations
Hypothesis
Experiment
Another outcome is
that certain behavior
is repeated many
times
Scientific Law is
developed
Description of how
things behave
Law - how
Theory- why
Observations
Hypothesis
Theory
(Model)
Modify
Experiment
Prediction
Law
Experiment
Law vs. Theory
Theory can’t be proved; always the
possibility that a new experiment will
disprove a theory
Law described a natural phenomenon,
but does not attempt to explain it
Frame of Reference
What is it?
Physics Definition- system of objects that are
not moving with respect to one another
Dictionary Definition- set of ideas, facts, or
circumstances within which something exists.
What does Frame of Reference mean to the
world of Chemistry?
What is Matter?
Matter is anything that takes up space
and has mass
Mass is the amount of matter in an
object
Mass is resistance to change in motion
along a smooth and level surface
Types of Matter
Substance- a particular kind of matter –
pure
Mixture- more than one kind of matter
Matter
We define matter as anything that has mass
and takes up space.
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Matter
Atoms are the building blocks of matter.
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Matter
Atoms are the building blocks of matter.
Each element is made of the same kind of atom.
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Matter
Atoms are the building blocks of matter.
Each element is made of the same kind of atom.
A compound is made of two or more different kinds of
elements.
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Classification of Matter
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Properties
and Changes
of Matter
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Properties
Words that describe matter (adjectives)
Physical Properties- a quality or
condition of a substance that can be
observed or measured without changing
the substance’s composition
Chemical Properties- a property that
can be observed by changing the type
of substance
Types of Properties
Intensive Properties…

Are independent of the amount of the
substance that is present.

Density, boiling point, color, etc.
Extensive Properties…

Depend upon the amount of the substance
present.

Mass, volume, energy, etc.
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Examples of Physical
Properties
1)
2)
3)
4)
5)
6)
7)
8)
9)
Color
Solubility
Odor
Hardness
Density
Melting Point
Boiling Point
Size
Shape
Types of Changes
Physical Changes

These are changes in matter that do not
change the composition of a substance.

Changes of state, temperature, volume, etc.
Chemical Changes

Chemical changes result in new substances.

Combustion, oxidation, decomposition, etc.
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Physical Changes
Physical Change- alters a substance
without changing its composition
Key Terms:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Boil
Freeze
Dissolve
Melt
Condense
Break
Split
Crack
Crush
Cutting
Chemical Reactions
In the course of a chemical reaction, the
reacting substances are converted to new
substances.
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Chemical Reactions
One or more substances changing into
a new substance
Starting Substance- Reactant
New Substance- Product
Iron + Sulfur  Iron Sulfide
How do you know?
I.
II.
III.
IV.
V.
VI.
6 Ways to Tell
Color Change
Energy absorbed or released (temp
change)
Gas or Solid Produced
Odor
Precipitate (ppt)- solid that separates from
solution
Not easily reversed
States of Matter
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States of Matter
Solid- matter that has a definite shape and
volume
Liquid- matter that flows and has a fixed
volume
Gas- matter that takes up both the shape
and volume of a container
Vapor- a substance that is currently a gas
but normally is a liquid or solid at room
temperature.
Plasma- matter consisting of a gaseous
mixture of electrons and positive ions. Not
States of Matter
Definite Definite Temp.
ComVolume? Shape? increase pressible?
Solid
Liquid
Gas
YES
YES
NO
YES
Small
Expans.
NO
NO
Small
Expans.
NO
NO
Large
Expans.
YES
Matter Chart
Properties: Solid
Liquid
Mass
Definite
Definite
Gas or
Vapor
Definite
Shape
Rigid
Indefinite
Indefinite
Volume
Definite
Definite
Indefinite
Temp.
Small
Moderate Large
Increase
Expansion Expansion Expansion
ComNo
No
Yes
Pressible?
Condense
Freeze
Evaporate
Melt
Solid
Liquid
Gas
Mixtures
Mixture- Physical blend of two or more
substances
Mixture has variable composition
Two Types of Mixtures
 Heterogeneous- not uniform in
composition
 Homogeneous- completely uniform in
compostion
Example
Heterogeneous
I.
Blood
II.
Chocolate Chip
Cookie
III. Soil
IV. Blood
V. Mixed Salad
Homogeneous
I.
Air
II.
Brass
III. Black Coffee
IV. Motor Oil
V. Water
Solutions
Homogeneous Mixture
Mixed molecule by molecule
Example: Sugar in Water (same
composition as any other portion)
Can occur between any state of matter
Common Solutions
 Gas in Gas- O2 in N (air)
 Liquid in Gas- Water Vapor
 Gas in Liquid- CO2 in Water (soda water)
 Liquid in Liquid- Acetic Acid in Water
(vinegar)
 Solid in Liquid- Kool Aid
 Solid in Solid- Copper in Silver (sterling
silver)
Solutions
Like all mixtures, they keep the
properties of the components
Can by separated by physical means
Not easily separated- can be separated
Separation
of Mixtures
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Distillation
Distillation uses
differences in the
boiling points of
substances to
separate a
homogeneous
mixture into its
components.
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Filtration
In filtration solid
substances are
separated from liquids
and solutions.
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Chromatography
This technique separates substances on the
basis of differences in solubility in a solvent.
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Separating
mixtures
Only a physical change- no new matter
Filtration- separate solids from liquids
with a barrier
Distillation- separate because of
different boiling points
Heat mixture
 Catch vapor in cooled area

Chromatography- different substances
are attracted to paper or gel, so move at
different speeds
The Metric System
Measuring
The numbers are only half of a
measurement.
It is 10 long.
10 what?
Numbers without units are meaningless.
How many feet in a yard?
A mile?
A rod?
The Metric System
Easier to use because it is a decimal
system.
Every conversion is by some power of 10.
A metric unit has two parts.
A prefix and a base unit.
prefix tells you how many times to divide
or multiply by 10.
Base Units
Length - meter - more than a yard - m
Mass - grams - about a raisin - g
Time - second - s
Temperature - Kelvin or ºCelsius K or ºC
Energy - Joules- J
Volume - Liter - half of a two liter bottle- L
Amount of substance - mole - mol
giga-
G
Prefixes
1,000,000,000 109
106
mega - M
1,000,000
kilo decicentimillimicronano-
103
0.1
10-1
0.01
10-2
0.001
10-3
0.000001
10-6
0.000000001 10-9
k
d
c
m
m
n
1,000
Volume
calculated by multiplying L x W x H
Liter the volume of a cube 1 dm (10 cm)
on a side
1L = 1 dm3
so 1 L = 10 cm x 10 cm x 10 cm
1 L = 1000 cm3
1/1000 L = 1 cm3
1 mL = 1 cm3
Conservation of Mass
Law of Conservation of Mass- in a
physical or chemical reaction, mass is
neither created nor destroyed; it is
conserved.
All mass can be accounted for.
Mass of the Reactants = Mass of
Products
Mass and Weight
Mass is measure of resistance to
change in motion
Weight is force of gravity.
Sometimes used interchangeably
Mass can’t change, weight can
Mass
Weight is a force. Mass is the amount of
matter.
1 gram is defined as the mass of 1 cm3
of water at 4 ºC.
1000 g = 1000 cm3 of water
1 kg = 1 L of water
1 kg = 2.5 lbs
Converting
k h
D
d
c
m
how far you have to move on this chart,
tells you how far, and which direction to
move the decimal place.
The box is the base unit, meters, Liters,
grams, etc.
Conversions
k h
D
d
c
m
convert 25 mg to grams
convert 0.45 km to mm
convert 35 mL to liters
It works because the math works, we
are dividing or multiplying by 10 the
correct number of times.
Uncertainty
Basis for significant figures
All measurements are uncertain to
some degree
Precision- how repeatable
Accuracy- how correct - closeness to
true value.
Random error - equal chance of being
high or low- addressed by averaging
measurements - expected
Accuracy versus
Precision
Accuracy refers to the proximity of
a measurement to the true value
of a quantity.
Precision refers to the proximity of
several measurements to each
other.
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Uncertainty
Systematic error- same direction each
time
Want to avoid this
Bad equipment or bad technique.
Better precision implies better accuracy
You can have precision without
accuracy
You can’t have accuracy without
precision (unless you’re really lucky).
Dimensional Analysis
Using the units to solve problems
Dimensional Analysis
Use conversion factors to change the units
Conversion factors = 1
1 foot = 12 inches (equivalence statement)
12 in = 1 = 1 ft.
1 ft.
12 in
2 conversion factors
multiply by the one that will give you the
correct units in your answer.
Examples
11 yards = 2 rod
40 rods = 1 furlong
8 furlongs = 1 mile
The Kentucky Derby race is 1.25 miles.
How long is the race in rods, furlongs,
meters, and kilometers?
A marathon race is 26 miles, 385 yards.
What is this distance in rods and
kilometers?
Examples
Because you never learned dimensional
analysis, you have been working at a
fast food restaurant for the past 35 years
wrapping hamburgers. Each hour you
wrap 184 hamburgers. You work 8
hours per day. You work 5 days a week.
you get paid every 2 weeks with a salary
of $840.34. How many hamburgers will
you have to wrap to make your first one
million dollars?
A senior was applying to college and wondered how
many applications she needed to send. Her counselor
explained that with the excellent grade she received in
chemistry she would probably be accepted to one
school out of every three to which she applied. She
immediately realized that for each application she
would have to write 3 essays, and each essay would
require 2 hours work. Of course writing essays is no
simple matter. For each hour of serious essay writing,
she would need to expend 500 calories which she
could derive from her mother's apple pies. Every three
times she cleaned her bedroom, her mother would
made her an apple pie. How many times would she
have to clean her room in order to gain acceptance to
10 colleges?
Units to a Power
How many m3 is 1500 cm3?
1500 cm3
1500
1m
1m
1m
100 cm 100 cm 100 cm
cm3
1m
100 cm
3
Units to a Power
How many cm2 is 15 m2?
36 cm3 is how many mm3?
Multiple units
The speed limit is 65 mi/hr. What is this in
m/s?
1 mile = 1760 yds
 1 meter = 1.094 yds

65 mi
hr
1760 yd
1m
1 hr 1 min
1 mi
1.094 yd 60 min 60 s
Multiple units
Lead has a density of 11.4 g/cm3. What
is this in pounds per quart?
454 g = 1 lb
 1 L = 1.094 qt

Temperature and
Density
Density
How heavy something is for its size.
The ratio of mass to volume for a
substance.
D=M/V
Independent of how much of it you have
gold - high density
air low density.
Density
Ratio of mass to volume
D = m/V
Useful for identifying a compound
Useful for predicting weight
An intrinsic property- does depend on
what the material is
Calculating
The formula tells you how.
Units will be g/mL or g/cm3
A piece of wood has a mass of 11.2 g
and a volume of 23 mL what is the
density?
A piece of wood has a density of 0.93
g/mL and a volume of 23 mL what is the
mass?
Density Problem
An empty container weighs 121.3 g. Filled
with carbon tetrachloride (density 1.53
g/cm3 ) the container weighs 283.2 g.
What is the volume of the container?
Density Problem
A 55.0 gal drum weighs 75.0 lbs. when
empty. What will the total mass be when
filled with ethanol?
density 0.789 g/cm3
1 gal = 3.78 L
1 lb = 454 g
Floating
Lower density floats on higher density.
Ice is less dense than water.
Most wood is less dense than water.
Helium is less dense than air.
A ship is less dense than water.
Density of water
1 g of water is 1 mL of water.
density of water is 1 g/mL
at 4ºC
otherwise it is less
Temperature
A measure of the average kinetic
energy
Different temperature scales, all are
talking about the same height of
mercury.
Derive a equation for converting ºF toºC
0ºC
Measuring
Temperature
Celsius scale.
water freezes at 0ºC
water boils at 100ºC
body temperature 37ºC
room temperature 20 - 25ºC
0ºC = 32ºF
0ºC
32ºF
100ºC = 212ºF
0ºC = 32ºF
0ºC
32ºF
100ºC 212ºF
How much it
changes
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
0ºC 100ºC
212ºF
32ºF
How much it
changes
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
1ºC = (180/100)ºF
1ºC = 9/5ºF
0ºC 100ºC
212ºF
32ºF
0ºC is not 0ºF
ºF
9
5
ºC
(0,32)= (C1,F1)
ºF
ºC
(0,32) = (C1,F1)
(100,212) = (C2,F2)
ºF
ºC
273
K
Measuring
Temperature
Kelvin starts at absolute zero (-273 º C)
degrees are the same size
C = K -273
K = C + 273
Kelvin is always bigger.
Kelvin can never be negative.
Temperature is different
from heat.
Temperature is which way heat will flow.
(from hot to cold)
Heat is energy, ability to do work.
A drop of boiling water hurts,
kilogram of boiling water kills.
Units of heat are
calories or Joules
1 calorie is the amount of heat needed
to raise the temperature of 1 gram of
water by 1ºC.
A food Calorie is really a kilocalorie.
How much energy is absorbed to heat
15 grams of water by 25ºC.
1 calorie = 4.18 J
Elements & Compounds
I.
II.
III.
Element- simplest form of matter
Elements can’t be separated
Elements are the building block
Smallest part is an atom
Compounds
I.
II.
III.
IV.
V.
Compound- formed by 2 or more
elements
Substances that can be separated into
simpler substances only by chemical
reactions
When broken down, the pieces have
completely different properties than the
compound
Pure substances
Represented by a formula
Smallest part is a molecule
Compound or Mixture
Compound
Mixture
One kind of pieceMolecules
More than one kind Molecule or atoms
Making is a
chemical change
Making is a
physical change
Only one kind
Variable composition
What is it?
1.
2.
3.
4.
5.
6.
7.
Element, Compound or Mixture
Silver
Orange Juice
Ice Tea
Potassium Chloride
Oxygen
Air
Pine Tree
Which is it?
Mixture
Element
Compound