Transcript Chapter 1 Introduction to Chemistry

Chapter 1
Introduction to Chemistry
What you’ll learn…
 You
will describe the relationships
between chemistry and matter
 You will recognize how scientific methods
can be used to solve problems
 You will distinguish between scientific
research and technology
Chemistry and Matter
 Chemistry is
the study of matter and the
changes that it undergoes
 Matter is anything that has a mass and
takes up space
 Mass
is a measurement that reflects the
amount of matter
 Is air matter?
 Weight
is a measurement not only of
the amount of matter but also the
effect of the Earth’s gravitational pull
on that matter
 Why
would scientists use “mass”
instead of “weight”?
 Macroscopic
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vs. Microscopic
Macroscopic matter does not need a
microscope to see it whereas microscopic
matter needs a microscope
Submicroscopic= atoms
•FYI: 1 million million atoms could fit onto
the period at the end of a sentence
Scientific Methods
 Observations
Qualitative Data- information that
describes
•Examples: color, odor, shape
 Quantitative Data- numerical
information
•Examples: how tall, how fast, how
much
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 Experiments
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Independent variable- variable that you plan
to change
Dependent variable- variable that changes in
response to a change in the independent
variable
Chapter 3
Matter- Properties and
Changes
What about Chapter 2???
(We’ll come back to that…)
Pure Substance
 Substance- matter
that has a uniform and
unchanging composition
 Examples: Table Salt, water, sugar
Physical Properties of Matter
A
physical property can be observed or
measured without changing the sample’s
composition

Examples: Density, Color, Odor, Taste,
Hardness, Melting Point, Boiling Point
Extensive vs. Intensive Properties
 Extensive
Properties are dependent upon the
amount of substance present
 Example: Mass
 Intensive Properties are independent of the
amount of substance present
 Example: Density, Color
Chemical Properties of Matter
 Chemical
property -the ability of a
substance to combine with or change into
one or more other substances
 Example: The ability of iron to form
rust when combined with oxygen
States of Matter
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Solid
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Liquid
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Definite shape
Definite volume
Flows
Constant volume
Takes the shape of its container
Gas
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Flows to conform to the shape of its container
Fills entire volume of container
Vapor- refers to the gaseous state of a substance that is a
solid or a liquid at room temperature
Physical Change
 Physical
changes alter
a substance without
changing its
composition

Example: cutting a
sheet of paper
•Indicating words: bend,
grind, crush, split,
melting, freezing,
condense
Chemical Changes
 AKA
Chemical Reaction
 A process that involves one or
more substances changing into new
substances
Conservation of Mass
 The
law of conservation of mass states
that matter is neither created nor
destroyed (it is conserved)
WOOD + OXYGEN

ASH + WATER VAPOR + CARBON DIOXIDE
Chemical or Physical Change?
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wind eroding rocks _________________________
dead leaves decaying __________________________
rain puddle drying up __________________________
mixing flour and baking powder__________________________
gasoline evaporating __________________________
hydrogen peroxide
decomposing__________________________
bread baking in an oven __________________________
instant tea dissolving in water __________________________
milk souring __________________________
gasoline burning __________________________
ANSWERS
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wind eroding rocks – PHYSICAL CHANGE
dead leaves decaying – CHEMICAL CHANGE
rain puddle drying up – PHYSICAL CHANGE
mixing flour and baking powder- PHYSICAL CHANGE
gasoline evaporating – PHYSICAL CHANGE
hydrogen peroxide decomposing- CHEMICAL CHANGE
bread baking in an oven – CHEMICAL CHANGE
instant tea dissolving in water – PHYSICAL CHANGE
milk souring – CHEMICAL CHANGE
gasoline burning- CHEMICAL CHANGE
Mixtures
A
mixture is a combination of two or more
substances in which each pure substance retains
its individual chemical properties
 Heterogeneous
Mixture- one that does
not blend smoothly throughout and which
the individual substances remain distinct
• Examples: Sand and Water, Oil and Water,
Cement
 Homogeneous
Mixture (Solutions)- has
constant composition throughout; it always
has a single phase
• Examples: salt water, vinegar, alloys
Separating Mixtures
1.
2.
3.
4.
Filtration- technique that uses a porous
barrier to separate a solid from a liquid
Distillation- technique that is based on
differences in the boiling points of substances
Crystallization- technique that results in the
formation of pure solid particles of a substance
from a solution containing the dissolved
substance
Chromatography- separates the components
of a mixture on the basis of the tendency of
each to travel or be drawn across the surface
of another material
Elements and Compounds
 Element-
a pure substance that cannot be
separated into simpler substances

Located on the periodic table in rows and
periods
• Periods= Horizontal Rows
• Groups= Vertical Columns
 Compound-
a combination of two or more
different elements that are combined
chemically
Law of Definite Proportions
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Elements comprising compounds combine in definite
proportions
 Regardless of the amount, a compound is always
composed of the same elements in the same
proportion by mass
Percent by Mass- the ratio of the mass of each element
to the total mass of the compound as a percentage
mass of element
percent by mass (%) 
x100
mass of compound
Practice Problem

A 78.0g sample of an unknown compound
contains 12.4 g of hydrogen. What is the
percent by mass of hydrogen in the compound?
12.4g
Percent by mass 
x100 
78.0g
15.9% Hydrogen
Material
Limestone
(CaCO3)
Soil
Bronze
Aluminum
Sugar + water
Concrete
Sterling Silver
Caffeine
Pure Substance or
Mixture
Element, Compound, Homogeneous,
Heterogeneous
ANSWERS
Material
Pure Substance or
Mixture
Element, Compound, Homogeneous,
Heterogeneous
PURE SUBSTANCE
COMPOUND
Soil
MIXTURE
HETEROGENOUS
Bronze
MIXTURE
HOMOGENOUS
PURE SUBSTANCE
ELEMENT
Sugar + water
MIXTURE
HOMOGENOUS
Concrete
MIXTURE
HETEROGENOUS
Sterling Silver
MIXTURE
HOMOGEN
PURE SUBSTANCE
COMPOUND
Limestone
(CaCO3)
Aluminum
Caffeine
 Homework 
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Page 9
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Page 13
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#15-17
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#1-5
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#12
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#6-8,10
#21-23
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#25-30 SKIP #28