Transcript Physical Science Chapter 1

Physical Science Chapter 15
The Classification of Matter
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15.1
Composition of Matter
The Big Idea:
Matter can be classified by
what it is made of, by its
physical properties, and by
its chemical properties.
Matter
 Matter is anything that has
mass and takes up space
15. The Classification of Matter
Composition of Matter:
Matter can be either a
 pure substance (an element or
a compound)
 mixture (either heterogeneous
or homogeneous.)
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15:1 The Composition of Matter
A. Substance are either
elements or compounds.
1. When all the atoms in a
substance are alike, the
substance is an element.
ex: Gold (Au) or Oxygen (O)
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15:1 The Composition of Matter
2. A compound is a substance
with two or more elements
combined in a fixed
proportion.
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15:1 The Composition of Matter
Elements
 All substances are built from atoms.
If all the atoms in a substance have
the same identity, that substance is
an element.
 The graphite in your
pencil point and the
copper coating of a
penny are examples
of elements.
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15:1 The Composition of Matter
Elements
 About 90 elements are found on
earth.
 More that 20 others have been
made in laboratories, but most of
these are unstable and exist only
for short periods of time.
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15:1 The Composition of Matter
Compounds
Can you imagine yourself putting
something made from a silvery
metal and a greenish-yellow,
poisonous gas on your food?
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The Composition of Matter
Compounds
 can not be broken down by physical means
 must be chemical means
15:1 The Composition of Matter
Compounds
• Table salt is a chemical
compound that fits this
description. Even
though it looks like
white crystals and
adds flavor to food, its
components—sodium
and chlorine—are
neither white nor salty.
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15:1 The Composition of Matter
Mixture
B. Two or more
substances that
can be easily
separated by
physical means
form a mixture
such as the pizza or
soft drink shown.
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15:1 The Composition of Matter
1. Heterogeneous Mixtures
• Each substance keeps its own
properties (each can be seen)
• Can be separated by physical means
(with your hands)
• Can have 1 or more states of matter
(solid, liquid, gas)
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Heterogeneous Mixtures
Examples
Bag of M&M’s
Jar of sand
Granite
Chocolate chip cookie
15:1 The Composition of Matter
• Most of the substances you come in
contact with every day are heterogeneous
mixtures. Some components are easy to
see, like the ingredients in pizza, but
others are not.
• For example, the cheese
in pizza is also a mixture,
but you cannot see the
individual components.
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15:1 The Composition of Matter
2. Homogeneous Mixtures
• Each substance loses its own properties
and takes on new properties.
• Looks the SAME throughout
• Can only have 1 phase (state of matter)
at a time
 Ex: salt, milk, air, soda
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15:1 The Composition of Matter
Homogeneous Compounds
• Soft drinks contain water, sugar,
flavoring, coloring, and carbon
dioxide gas.
• Soft drinks in
sealed bottles are
examples of
homogeneous
mixtures.
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15:1 The Composition of Matter
3. Another name for homogeneous
mixtures like a cold soft drink is
solution.
A solution is a homogeneous
mixture of particles so small
they cannot be seen without
a microscope and will never
settle to the bottom of the
container.
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15:1 The Composition of Matter
• Solutions
remain
constantly
and
uniformly
mixed.
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15:1 The Composition of Matter
Colloids
• Milk is an example of a specific kind
of mixture called a colloid.
4. A colloid is a type of
heterogeneous mixture with
particles that are larger than
those in solutions but not heavy
enough to settle out.
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Colloid Examples
 Jello
 Ice cream
 Paint
 Fog/Smoke
 shampoo
15:1 The Composition of Matter
Detecting Colloids
• One way to distinguish a colloid from a
solution is by its appearance.
• Fog appears white because its particles
are large enough to scatter light.
• Sometimes it is not so obvious that a
liquid is a colloid.
• You can tell for certain if a liquid is a colloid
by passing a beam of light through it.
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Detecting Colloids
• A light beam is invisible as it passes
through a solution, but can be seen readily
as it passes through a colloid. This occurs
because the particles in the colloid are
large enough to scatter light, but those in
the solution are not. A solution does not
scatter light.
• The scattering of
light by colloidal
particles is called
the Tyndall effect.
15:1 The Composition of Matter
4. Suspensions—a heterogeneous
mixture containing a liquid in which
visible particles settle.
• Some mixtures are neither solutions nor
colloids. One example is muddy pond water.
• Pond water is a suspension, which is
a heterogeneous mixture containing a
liquid in which visible particles settle.
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15.2 Properties of Matter
The Big Idea:
A physical property can be
observed without changing the
identity of the material. A
chemical property describes
whether it can undergo a
chemical change.
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15.2
15.2
Properties of Matter
A. Physical Property—
characteristic of a material
which can be observed without
changing the identity of the
substance in material.
• Examples of physical properties are color,
shape, size, density, melting point, and
boiling point.
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15:2 Physical Properties
Appearance physical description of a substance
• How would you describe a tennis ball? You
could begin by describing its shape, color, and
state of matter.
• You can measure
some physical
properties, too. For
instance, you could
measure the diameter
of the ball.
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15:2 Physical Properties
Behavior: how a substance acts
• Some physical properties describe the
behavior of a material or a substance.
• Attraction to a magnet is
a physical property of
the substance iron.
• Every substance has a
specific combination of
physical properties that
make it useful for certain
tasks.
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15:2 Physical Properties
1. Appearance –physical description of a
substance
2. Behavior—how a substance acts; for
example, magnetism, viscosity, ductility
3. Physical properties such as size and
magnetism can be used to separate
mixtures.
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15:2 Physical Properties
Using Physical Properties to Separate
• Look at the mixture of iron filings and
sand shown.
• You probably won’t be
able to sift out the iron
filings because they are
similar in size to the
sand particles. What
you can do is pass a
magnet through the
mixture.
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15:2 Physical Properties
B. Physical Change—change in a
substance’s size, shape or state of
matter.
1. Substance does not change
identity when it undergoes a
physical change.
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15:2 Physical Properties
The Identity Remains the Same
• Iron is a substance that can change states if it
absorbs or releases enough energy—at high
temperatures, it melts.
• Color changes can
accompany a physical
change, too.
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15:2 Physical Properties
The Identity Remains the Same
• For example,
when iron is
heated it first
glows red.
Then, if it is
heated to a
higher
temperature, it
turns white.
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15:2 Physical Properties
2. Distillation is a process for
separating a mixture by
evaporating a liquid and
condensing its vapor.
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15:2 Physical Properties
Distillation
• The process for
separating substances
in a mixture by
evaporating a liquid
and recondensing its
vapor is distillation.
• It usually is done in
the laboratory using
an apparatus similar
to that shown.
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Examples of Physical Changes
•
•
•
•
crumpling a sheet of paper
melting an ice cube
casting silver in a mold
breaking a bottle
15:2 Chemical Properties and Changes
A chemical property a property
used to characterize materials in
reactions that change their identity.
• The tendency of a substance to burn, or its
flammability, is an example of a chemical
property because burning produces new
substances during a chemical change.
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15:2 Chemical Properties and Changes
D. When one substance changes
to another substance, a chemical
change has occurred.
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15:2 Chemical Properties and Changes
The Identity Changes
• Clues such as heat, cooling, or the formation of
bubbles or solids in a liquid are helpful
indicators that a reaction is taking place.
• However, the only sure proof is that a new
substance is produced.
• The only clue that iron has changed into
a new substance is the presence of rust.
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15:2 Chemical Properties and Changes
1. Some chemical changes are
indicated by temperature change,
smell, or bubble formation.
• Tarnish is a chemical reaction between silver
metal and sulfur compounds in the air which
results in silver sulfide.
• It can be changed back into silver using a
chemical reaction.
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15:2 Chemical Properties and Changes
2. Other chemical changes
occur very slowly such as the
formation of rust.
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Chemical Change
When the composition of the
substance changes
Chemical Change
How to know a chemical
change has occurred:
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•
•
•
•
•
Color changes
Absorbing or releasing energy
Produces an Odor
Precipitate (formation of solid)
Production of Gas
Burning
Chemical Change
Examples:
Rusting of nail
Mold on food
Bleaching
Fireworks exploding
Burning toast
Leaves changing color
15:2
The Conservation of Mass
• Suppose you
burn a large log
until nothing is
left but a small
pile of ashes.
• At first, you might think that matter was lost
during this change because the pile of ashes
looks much smaller than the log did.
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The Conservation of Mass
• In fact, the
mass of the
ashes is less
than that of
the log.
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The Conservation of Mass
• However, suppose that
you could collect all the
oxygen in the air that
was combined with the
log during the burning
and all the smoke and
gases that escaped from
the burning log and
measure their masses,
too.
• Then you would find that no mass was
lost after all.
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17:2 Conservation of Mass
The law of conservation of
mass
matter can neither be created
or destroyed.
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The Conservation of Mass
• Not only is no mass
lost during burning,
mass is not gained or
lost during any
chemical change.
F. According to the law of conservation
of mass, the mass of all substances that
are present before a chemical change
equals the mass of all the substances
that remain after the change.
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15:2 Math Skills
Mass of reactants = mass of products
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