Transcript Ch 3 Matter & Change

Matter – Properties and Changes
What is Matter?
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Matter is anything that takes up space and
has mass.
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Mass is the amount of matter in an object.
Types of Matter
Matter
Pure Substance
Elements
Examples:
Compounds
Mixtures
Heterogeneous
Homogeneous
Properties
Words that describe matter (adjectives)
 Physical Property - a property that can
be observed and measured without
changing the substance.
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Examples:
Chemical Property - a property that can
only be observed by changing the type
of substance.
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Examples:
States of matter
Solid- matter that can not flow and has
definite volume.
 Liquid- definite volume but takes the shape
of its container (flows).
 Gas- a substance without definite volume or
shape and can flow.
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Vapor- a substance that is currently a gas but
normally is a liquid or solid at room temperature.
States of Matter
Definite Definite
Volume? Shape?
Solid
Liquid
Gas
YES
YES
NO
Expansion w/
Temp.
increase
Compressible?
YES
Small
Expans.
NO
NO
Small
Expans.
NO
NO
Large
Expans.
YES
Condense
Freeze
Melt
Solid
Deposition
Liquid
Sublimation
Boil
Gas
States of Matter
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Plasma:
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Occurs at high temperature low pressure
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Formed when electrons separate from nucleus
of gases
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Most common state of matter in the universe
Changes in Matter
Physical Changes & Chemical Changes
Physical Changes
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These alter the appearance of matter without
changing its composition.
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Examples?
Changes of the state (or phase) of matter is
a physical change
 The temperature & pressure at which matter
changes phase are important physical
properties
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These are melting & boiling points
Another Way to Change
States
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Pressure
For some substances it will turn solids to liquids
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For others it will turn liquids to solids
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Ex: Silly Putty
Will turn gas to liquid
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EX: Ice Skating
Compressor in refrigerator and AC
Will turn gas to solid
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Formation of Dry Ice
Chemical Changes
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Occur when one or more substances react
and form a new substance
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These are also called chemical reactions
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Products of the chemical reactions ALWAYS
have different properties than the original
materials
Evidence of Chemical
Reactions:
Formation of a gas
 Formation of a solid
 Drastic color change
 Energy changes – temp. changes or
formation of light
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Exothermic vs. Endothermic Reactions
Change in the smell of a substance
Conservation of Mass
Mass can not be created or destroyed in
ordinary chemical changes
 All the mass can be accounted for
 Mass at the start = mass at end
 So the total mass of the products should
equal the total mass of the reactants
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Antoine Lavoisier
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Considered the father
of modern Chemistry
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Discovered the Law of
Conservation of Mass
(also called the Law of
Conservation of
Matter)
Did experiments on
reactions.
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Mixtures
A physical combination of two or more
substances
 Heterogeneous - you can see the individual
substances that make it up.
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Ex: Chocolate chip cookie dough, gravel, soil.
Homogeneous- you cannot see the individual
substances that make it up, it always has a
single phase.
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Ex: Kool-aid, air.
Solutions
Another name for homogeneous mixture
 Can occur between any state of matter.
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Examples:
 Liquid
 Solid
 Gas
Separating mixtures
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Only physical changes - no new matter formed
Filtration- separate solids from liquids with a barrier
Distillation- separate because of different boiling
points
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Heat mixture
Catch purified vapor in cooled area
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Chromatography- different substances are
attracted to paper or gel, so move at
different speeds
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Crystallization – pure solids form when solid
particles come out of solution (make
crystals)
Elements & Compounds
Section 3.4
Elements
Simplest pure substance
 Cannot be broken down into simpler matter by
normal physical or chemical means
 All one kind of atom
 Each one has a unique name and symbol. In
the symbol the first letter is always capitalized
and the remaining letter(s) are lowercase.
 There are 91 naturally occurring elements
 Who was given credit for organizing them into a
table?
Dmitri Mendeleev
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Compounds
Chemical combinations of two or more
different elements
 When they are broken down, the pieces
have completely different properties than the
compound.
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For example: Salt
Most of the substances we work with are
compounds
Chemical Symbols
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Used to write chemical formulas
You know it is a formula because there will be
more than one capital letter
Subscripts tell us how many of each atom in the
formula.
H2O
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C3H8
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HBrO3
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Laws of Compounds
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By accounting for the mass of all matter
there are a couple of laws that govern how
compounds are created.
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Law of Definite Proportions
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Law of Multiple Proportions
Law of Definite
Proportions
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Each compound has a specific ratio of elements by
mass
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For example – the chemical formula for water is
always H2O
You can also see its ratio by mass:
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It is always a whole # ratio
Water is always 8 grams of oxygen for each gram of
hydrogen
This does not change, no matter where you are on
Earth! (Or in the universe for that matter)
Law of Def. Prop.
Continued…
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This law can be verified by determining the
percent by mass of the elements in a
compound:
 mass of element 
Percent by mass (%) = 
 x100
 mass of compound 
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Example: A compound contains 52.46 g of
iron and 22.54 g of oxygen. What is the
percent composition of oxygen?
30.05 % Oxygen
Law of Multiple
Proportions
The textbook states that when the same
elements combine to make different
compounds, they combine in small whole
number ratios.
 You will NOT get fractions of elements
 Examples:
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CuCl vs. CuCl2
 CH4 vs. C2H6
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Review
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What makes a form of matter a substance? What are some
examples?
How do you distinguish between chemical and physical
properties?
What is the difference between a physical change and a
chemical change? Give one example of each.
Why is a solution a homogeneous mixture? What is one
way to separate a homogeneous mixture?
Explain how you would tell that NaCl is a compound but Na
is an element.
Explain how all compounds obey the laws of definite and
multiple proportions.