chemistry - matter · pdf filewhat is chemistry? •“chemistry is the study of the...
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Chemistry – Matter Unit
• What is matter?
• What is
chemistry?
• What is the
organization of
matter?
• What is the
nature of matter?
Is Air matter?
• What are the two criteria for matter?
–Does it take up space?
–Does it have mass?
What is chemistry?
• “Chemistry is the study of the composition, structure, and the properties of matter and the changes it undergoes.”
What is the composition of matter?
Matter
Pure Matter
SubstanceImpure Matter
Mixture
What is a pure substance?
• A pure substance has a definite composition (proportion).
• The composition of a substance will have the same percent of elements no matter where the sample was obtained.
– Water from Lake Okechobee and water from the Atlantic Ocean (once cleaned up) will have the same composition of hydrogen to oxygen.
– Gold is the same as other gold (once cleaned up).
What is a pure substance?
• A pure
substance, by
definition, is an
element or a
compound.
• A container with
an almost pure
compound:
Pure Substance
Pure Substance
Element Compound
What is an element?
• “a pure substance made of only one kind
of atom”
• A substance that cannot be decomposed
any farther by simple chemical means
• An element has a definite composition.
Gold from South Africa is the same, when
purified, as a sample from California.
Periodic Table of Elements
• Most elements on the periodic chart are metals.
• Elements past 110 have been discovered and made but
are unstable
Elemental Samples
• Zinc, copper, lead, carbon, sulfur
What is a compound?
• “A compound is a substance
that is made from the atoms of
two or more elements that are
chemically bonded.”
• The definition is actually more
involved than this.
What is a compound?
• A compound is a substance that
cannot be decomposed any farther by
simple physical means.
• A compound has a definite
composition by mass.
• A compound is made up of two or
more elements chemically combined.
What is a compound?
• A compound no longer has the
properties of its constituent
elements.
• Table salt, NaCl or sodium
chloride, is a compound of the
element sodium and the element
chlorine.
Sodium
Sodium metal
• Soft, can be
cut with a knife
• Shiny
• Good
conductor of
electricity
• Very reactive
Sodium in water
Chlorine gas
Chlorine gas
• Greenish gas
• Poisonous
• Heavier than
air
Sodium in chlorine gas
Sodium chloride, NaCl
• Sodium chloride dissolves in water
rather than reacts with water.
• Sodium chloride is a white solid, not a
poisonous green gas.
• Sodium chloride is its own substance
with its own properties, not those of
either sodium or chlorine.
Samples of Other Compounds
• Sucrose (table sugar), Sodium Chloride, Water, Copper(II) sulfate
Colored Compounds
• Cobalt(II) chloride, Iron(II) sulfate, Potassium dichromate, Potassium chromate, Nickel(II)
nitrate, copper(II) sulfate
What is the composition of
matter?Matter
Pure Substance Impure Matter
Mixture
Impure Matter - Mixture
• “A mixture is a blend of two or
more kinds of matter, each of
which retains its own identity and
properties.”
• A mixture is made up of two or
more substances that are not
chemically combined.
Mixtures
• Mixtures can be separated by simple
physical means.
• Two mixtures containing the same
substances may not have the same
proportions.
• Example: Very salty water versus
barely salty water. Very sweet sugar
water versus slightly sweet sugar
water.
Water and Dye Mixture
• Two mixtures of the same substances may
have different proportions.
Mixtures
Mixtures
Homogeneous
Mixture
Heterogeneous
Mixture
Solutions
• Mixtures
– Mixture = a blend of two or more kinds of
matter, each of which retains its own
identity and properties
a) homogeneous mixture = a mixture that
is uniform in composition throughout
Ex: Food coloring and water
b) heterogeneous mixture = a mixture that
is NOT uniform in composition throughout
Ex: Oil and water
Heterogeneous Mixtures
• Sand and water on the left and sand and
gravel on the right.
THE NATURE OF SOLUTIONS:
1) Solvent = the substance that does the dissolving in a solution
a) Typically present in the greatest amount
b) Typically a liquid
c) Water is the most common or “universal” solvent
2) Solute = substance being dissolved in a solution
a) Typically present in the least amount
b) Typically a solid
Chemical Separation Methods
• Heat the compound.
Chemical Separation Methods
• Use Electrolysis
which is using an
electric current to
decompose the
compound.
• An electrolyte has
been added to the
water since water
does not conduct.
Mixtures
• How can mixtures be separated?
–Use Physical Separation
Methods.
What are examples of physical
separation methods?
Physical Separation Methods
• Distillation is the
separation of
mixtures by using
the difference in
boiling points of
liquids.
• A water cooled
condenser is used.
Physical Separation Methods
• Filtration uses
the difference in
particle size to
separate
mixtures.
• Filter papers
have different
size pores.
Physical Separation Methods
• Chromatography
uses the difference
in solubility in
various solvents.
• Gas, liquid, thin
layer, and paper
chromatography
are widely used.
States of Matter
• Three states of matter:
• Liquid, solid, gas
Physical Changes
• During physical changes matter
changes in appearance without
forming new substances.
• What some examples of physical
changes?
Physical Change Examples
• Breaking or tearing
Physical Change Examples
• Boiling or condensing
Physical Change Examples
• Freezing or melting
Physical Change Examples
• Sublimation
Physical Change Examples
• Sublimation:
• “The change of state directly to a gas
is known as sublimation.”
• “The reverse process is called
deposition, the change of state from
a gas directly to a solid.”
Chemical Changes
• During chemical changes new
substances are formed with
different properties than the
original substances.
• What is an example of a chemical
change?
Chemical Change Example
• Heating baking soda, sodium hydrogen
carbonate, forms sodium carbonate,
carbon dioxide, and water. The formation
of carbon dioxide is what causes cakes to
rise.
Mixture or Pure Substance
• These bottles contain sodium chloride,
sucrose, and a mixture of the two. Which
is which and how can they be identified?
Physical and Chemical
Properties
• What are some physical propertiesof this pen?
Physical Properties
• Examples:
–Color
–Hardness
–Texture
–Volume
–Length
–Mass
Physical Properties
• More Examples:
–Density (mass/volume ratio)
–Odor
–Sound
–Boiling point
–Melting point
–Magnetism
Physical Properties
• Melting Point and freezing point temperatures are the same.
Chemical Properties• A chemical
property is how something reacts.
• Does the pen float
• Physical
• Does the pen dissolve
• Physical
• Does the pen react with water
• chemical.
Chemical Properties
• Does the pen burn
• chemical property.
• Whether and how something reacts
• chemical.
Extensive vs Intensive
• Extensive Properties depend upon
the amount of matter that is present.
• Intensive Properties do not depend
on the amount of matter present.
These properties are the same for a
given substance regardless of how
much of the substance is present.
Periodic Table
The horizontal rows of the periodic table are called PERIODS.
The vertical columns of the periodic table are called GROUPS, or FAMILIES.
The elements in any groupof the periodic table havesimilar physical and chemicalproperties!
silicon
Metals:
The noble gases are colorless, odorless, tasteless, and
nonflammable under standard conditions. They are also
sometimes called the "inert gasses" due to their lack of
reactivity with other chemicals.
Non-Metals
Non-metals are not able to conduct electricity or heat very well,
are very brittle, and cannot be rolled into wires or pounded into
sheets. The non-metals exist in two of the three states of
matter at room temperature: gases (such as oxygen) and
solids (such as carbon). The non-metals have no metallic
luster, and do not reflect light
Metalloids:
Metalloids are the elements found along the stair-step line that
separates metals from non-metals. Some of the metalloids, such as
silicon and germanium, are semi-conductors. This means that they can
carry an electrical charge under specific conditions. This property
makes metalloids useful in computers and calculators microchips.
Nobel Gases:
Metalloids are the elements found along the stair-step line that
separates metals from non-metals. Some of the metalloids, such as
silicon and germanium, are semi-conductors. This means that they can
carry an electrical charge under specific conditions. This property
makes metalloids useful in computers and calculators microchips.