Chapter 3
Matter – Properties and Changes
Section 1
Properties of Matter
Section 1: Properties of Matter
Most common substances exist as solids, liquids, and gases, which
have diverse physical and chemical properties.
K
What I Know
W
What I Want to Find Out
L
What I Learned
Substances
Matter is anything that has mass and takes up space. Matter is everything around
us. Matter with a uniform and unchanging composition is a substance. Much of
your chemistry course will be focused on the composition of substances and how
they interact with one another.
Properties of Matter
States of Matter
The physical forms of matter, either solid, liquid, or gas, are called the states of
matter.
Solids are a form of matter that have their own definite
shape and volume.
Liquids are a form of matter that have a definite
volume but take the shape of the container.
Properties of Matter
States of Matter
Gases have no definite shape or volume. They expand
to fill their container.
Vapor refers to the gaseous state of a substance that is
a solid or liquid at room temperature.
Properties of Matter
Physical Properties
• Let’s play 20 Questions!
QUESTIONS
QUESTIONS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Physical Properties of Matter
A physical property is a characteristic that can be observed or measured
without changing the sample’s composition.
-ex: viscosity, hardness, density, malleability, melting point, boiling point, etc.
Properties of Matter
Physical Properties of Matter
Extensive properties, such as mass, length, and volume, are dependent on the
amount of substance present.
Intensive properties, such as density, are dependent on the what the substance
is not how much there is.
Properties of Matter
Chemical Properties of Matter
The ability of a substance to combine with or change into one or more other
substances is called a chemical property. Examples include:
• Iron forming rust
• Copper turning green in the air
• Flammability
• Reactivity
Properties of Matter
Observing Properties of Matter
A substance can change form—an important concept in chemistry. Both physical
and chemical properties can change with specific environmental conditions, such
as temperature and pressure.
Properties of Matter
Physical & Chemical Properties
Physical & Chemical Properties Song
Essential Questions
• What characteristics identify a substance?
• What distinguishes physical properties from chemical
properties?
• How do the properties of the physical states of matter differ?
Properties of Matter
Section 2
Changes in Matter
Section 2: Changes in Matter
Matter can undergo physical and chemical changes.
K
What I Know
W
What I Want to Find Out
L
What I Learned
Physical Changes
A change that alters a substance without changing its composition is known as a
physical change. A phase change is a transition of matter from one state to
another. Boiling, freezing, melting, and condensing all describe phase changes in
chemistry.
Changes in Matter
Phase Changes
• Phase change- reversible
physical change that occurs
when a substance changes
from one state of matter to
another.
• Melting, freezing,
vaporization,
condensation, sublimation,
and deposition are the six
common phase changes.
Energy and Phase Changes
• During a phase change, energy is transferred
between a substance and its surroundings.
• Energy is either absorbed or released during a
phase change.
MELTING
• Heat flows from the air to the ice. As ice gains
energy, the molecules vibrate more quickly. At
the melting point of water, 0ºC, some
molecules have enough energy to overcome
the attractions and move.
• When all the molecules have enough energy
to move, melting is complete. Any additional
energy will cause the temperature to rise.
FREEZING
• When liquid is placed in a freezer, energy flows
from the liquid to the air in the freezer. The
water cools down. Kinetic energy decreases,
particles move more slowly and begin to arrange
themselves in an orderly pattern.
• Freezing is exothermic because it gives off energy
to the surroundings.
• Freezing does not mean “cold.” Silicon freezes at
1412 ºC
VAPORIZATION
• When a substance changes from a liquid to a
gas. The substance must absorb energy.
In a refrigerator, a pair of phase changes keep
the food cold. Energy from inside the food
compartment is used to change a liquid to a
gas in the evaporator. This energy is released
when the compressed gas changes back to a
liquid in the condenser
Condensation
• CONDENSATION
– The phase change in which a substance changes
from gas to liquid.
Water vapor from the air condensed into drops of liquid water on these blades of
grass
More Phase Changes
• SUBLIMATION
– Phase change in which a
substance changes from a
solid to a gas without first
changing to a liquid. Ex:
Dry ice
• DEPOSITION
– Phase change when a gas
changes directly into a
solid without first
changing to a liquid. Ex:
Frost
The trap is baited with dry ice because
mosquitoes are attracted to carbon dioxide.
Chemical Changes
A change that involves one or more substances turning into new substances is
called a chemical change. Decomposing, rusting, exploding, burning, or
oxidizing are all terms that describe chemical changes.
Changes in Matter
Physical vs Chemical Change
http://www.youtube.com/watch?v=g
Cbqjs-pqJo
Gummy Bear torture
http://www.youtube.com/watch?v=u
j9D3mc7tVg
Law of Conservation of Mass
The law of conservation of mass states that mass is neither created nor
destroyed in a chemical reaction, it is conserved. The mass of the reactants
equals the mass of the products.
massreactants = massproducts
Changes in Matter
CONSERVATION OF MASS
KNOWN
UNKNOWN
mmercury(II) oxide = 10.00 g moxygen = ? g
EXAMPLE
mmercury = 9.26 g
Problem
In an experiment, 10.00 g of red mercury(II)
oxide powder is placed in an open flask and
heated until it is converted to liquid mercury
and oxygen gas. The liquid mercury has a
mass of 9.26 g. What is the mass of oxygen
formed in the reaction?
Response
ANALYZE THE PROBLEM
You are given the mass of a reactant and the
mass of one of the products in a chemical
reaction. According to the law of mass
conservation, the total mass of the products
must equal the total mass of the reactants.
SOLVE FOR THE UNKNOWN
•
State the law of conservation of mass.
Massreactants = Massproducts
mmercury(II) oxide = mmercury + moxygen
•
Solve for m oxygen.
moxygen = mmercury(II) oxide − mmercury
•
Substitute mmercury(II) oxide = 10.00 g and
mmercury = 9.26 g.
moxygen = 10.00 g − 9.26 g
moxygen = 0.74 g
Section Title
Essential Questions
• What is a physical change and what are several common
examples?
• What defines a chemical change? How can you recognize a
chemical change?
• How does the law of conservation of mass apply to chemical
reactions?
Changes in Matter
Section 3
Mixtures of Matter
Section 3: Mixtures of Matter
Most everyday matter occurs as mixtures—combinations of two or more
substances.
K
What I Know
W
What I Want to Find Out
L
What I Learned
Mixtures
A mixture is a combination of two or more pure substances in which each
pure substance retains its individual chemical properties.
A homogenous mixture is a mixture where the composition is constant
throughout. Homogeneous mixtures are also called solutions.
A heterogeneous mixture is a mixture where the individual substances
remain distinct.
Mixtures of Matter
Separating Mixtures
Filtration is a technique that uses a porous barrier to separate a solid from
a liquid in a heterogeneous mixture.
Distillation is a separation technique for homogeneous mixtures that is
based on the differences in boiling points of substances.
Crystallization is a separation technique for homogenous mixtures that
results in the formation of pure solid particles from a solution containing the
dissolved substance.
Mixtures of Matter
Separating Mixtures
Sublimation is the process of a solid changing directly to a gas, which can
be used to separate mixtures of solids when one sublimates and the other
does not.
Chromatography is a technique that separates the components of a
mixture on the basis of tendency of each to travel across the surface of
another material.
Mixtures of Matter
Essential Questions
• How do mixtures and substances differ?
• Why are some mixtures classified as homogeneous, while
others are classified as heterogeneous?
• What are several techniques used to separate mixtures?
Mixtures of Matter
Section 4
Elements and Compounds
Section 4: Elements and Compounds
A compound is a combination of two or more elements.
K
What I Know
W
What I Want to Find Out
L
What I Learned
Elements
An element is a pure substance that cannot be separated into simpler
substances by physical or chemical means.
•
92 elements occur naturally on Earth.
•
Each element has a unique name and a one, two, or three-letter
symbol.
•
The periodic table organizes the elements into a grid of horizontal
rows called periods and vertical columns called groups.
•
Elements in the same group have similar chemical and physical
properties.
•
The table is called periodic because the pattern of similar properties
repeats from period to period.
Elements and Compounds
Compounds
A compound is a made up of two or more elements combined chemically.
•
Most of the matter in the universe exists as compounds.
•
Table salt, NaCl, and water, H2O, are compounds.
•
Unlike elements, compounds can be broken into smaller components
by chemical means.
Elements and Compounds
Compounds
Separating a compounds into its
elements often requires external
energy, such as heat or electricity.
This figure shows electrolysis of
water to form hydrogen and oxygen
gas.
Elements and Compounds
Law of Definite Proportions
The law of definite proportions states that a compound is always composed
of the same elements in the same proportion by mass, no matter how large or
small the sample.
Example: Water is always composed of 2 Hydrogen to 1 Oxygen
The relative amounts are expressed as percent by mass, the ratio of the
mass of each element to the total mass of the compound expressed as a
percentage.
Elements and Compounds
Law of Definite Proportions
This table demonstrates that the percentages of elements in sucrose remain
the same despite differences in sample amount.
Elements and Compounds
Law of Multiple Proportions
The law of multiple proportions states that when different compounds are
formed by a combination of the same elements, different masses of one
element combine with the same relative mass of the other element in whole
number ratios.
Example: Peroxide, H2O2, and water, H2O
•
•
Different compounds formed from the same elements.
Hydrogen mass the same in both compounds but oxygen mass is a 2:1
ratio in peroxide to water.
Elements and Compounds
Law of Multiple Proportions
Elements and Compounds
Essential Questions
• What distinguishes elements from compounds?
• How is the periodic table organized?
• What are the laws of definite and multiple proportions and
why are they important?
Elements and Compounds