Transcript Chemistry: Matter and Change

Matter—Properties and Change
Section 3.1 Properties of Matter
Section 3.2 Changes in Matter
Section 3.3 Mixtures of Matter
Section 3.4 Elements and
Compounds
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Section 3.1 Properties of Matter
• Identify the characteristics of a substance.
• Distinguish between physical and chemical
properties.
• Differentiate among the physical states of matter.
density: a ratio that compares the mass of an
object to its volume
Section 3.1 Properties of Matter (cont.)
states of matter
physical property
solid
extensive property
liquid
intensive property
gas
chemical property
vapor
Most common substances exist as
solids, liquids, and gases, which have
diverse physical and chemical
properties.
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.
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.
States of Matter (cont.)
• 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.
Physical Properties of Matter
• A physical property is a characteristic that
can be observed or measured without
changing the sample’s composition.
Physical Properties of Matter (cont.)
• Extensive properties are dependent on
the amount of substance present, such as
mass, length, or volume.
• Intensive properties are independent of the
amount of substance present, such as
density.
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.
– Iron forming rust
– Copper turning green in the air
Observing Properties of Matter
• A substance can change form–an
important concept in chemistry.
• Chemical properties can change with specific
environmental conditions, such as
temperature and pressure.
Section 3.2 Changes in Matter
• Define physical change and list several common
physical changes.
• Define chemical change and list several indications
that a chemical change has taken place.
• Apply the law of conservation of mass to chemical
reactions.
observation: orderly, direct information gathering
about a phenomenon
Section 3.2 Changes in Matter (cont.)
physical change
phase change
chemical change
law of conservation of mass
Matter can undergo physical and
chemical changes.
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.
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.
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
Section 3.3 Mixtures of Matter
• Contrast mixtures and substances.
• Classify mixtures as homogeneous or
heterogeneous.
• List and describe several techniques used to
separate mixtures.
substance: a form of matter that has a uniform and
unchanging composition; also known as a pure
substance
Section 3.3 Mixtures of Matter (cont.)
mixture
distillation
heterogeneous mixture
crystallization
homogeneous mixture
sublimation
solution
chromatography
filtration
Most everyday matter occurs as
mixtures—combinations of two or more
substances.
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.
Mixtures (cont.)
• Homogeneous mixtures are also called
solutions.
• A heterogeneous mixture is a mixture where
the individual substances remain distinct.
Mixtures (cont.)
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.
Separating Mixtures (cont.)
• 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.
Section 3.4 Elements and Compounds
• Distinguish between elements and compounds.
• Describe the organization of elements in the periodic
table.
• Explain how all compounds obey the laws of definite
and multiple proportions.
proportion: the relation of one part to another or
to the whole with respect to quantity
Section 3.4 Elements and Compounds
(cont.)
element
law of definite proportions
periodic table
percent by mass
compound
law of multiple proportions
A compound is a combination of two or
more elements.
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.
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.
Compounds
(cont.)
• Elements can never be separated.
• Compounds can be broken into components
by chemical means.
Compounds
(cont.)
• This figure shows
electrolysis of
water to form
hydrogen and
oxygen.
Compounds
(cont.)
• The properties of a compound are different
from its component elements.
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.
Law of Definite Proportions
(cont.)
• 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.
Law of Definite Proportions
(cont.)
• This table demonstrates that the percentages
of elements in sucrose remain the same
despite differences in sample amount.
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.
– H2O2 and H2O
– Copper(I) chloride and copper(II) chloride
Law of Multiple Proportions (cont.)