Chem 161
Chapter 1: Matter, Energy, and
the Origins of the Universe
Problems: 1.1-1.10, 1.14-1.22, 1.24-1.93, 1.96
Chapter 1: Matter, Energy, and
the Origins of the Universe
• Science: study of nature that results in a logical
explanation of the observations
• Chemistry: study of matter, its properties, and the
changes it undergoes
• In what fields is chemistry used today? How is it
used?
1.2 Matter: An Atomic View
• We study matter at different levels:
– macroscopic: the level which we can observe with the
naked eye (geologists study rocks at the macroscopic
level)
– microscopic: the level which we can observe using a
microscope (scientists study tiny animals, plants, or
crystals at the microscopic level)
– atomic or molecular (also called particulate):
• at the level of atoms and molecules
• can only be “observed” using the most powerful
microscopes
• most atoms and molecules are a few nanometers in
size
The term “nanotechnology” refers to materials created or
developed by manipulating atoms and/or molecules
1.1 Classes of Matter
• matter: anything that has mass and
occupies volume
• Types of matter we deal with:
– pure substances (elements &
compounds): a single chemical
consisting of only one kind of
matter
– mixtures (homogeneous &
heterogeneous): Two or more
pure substances can combine to
form mixtures
Pure Substances
• Two types of pure substances:
– elements:
• consist of only one type of atom
• atoms cannot be broken down into smaller
components by chemical reaction
– Examples: copper wire (Cu), sulfur powder (S8),
sodium (Na), barium (Ba), hydrogen gas (H2),
oxygen gas (O2), and chlorine gas (Cl2).
– compounds:
• consist of more than one type of atom and have a
specific chemical formula
– Examples include hydrogen chloride (HCl), water
(H2O), sodium chloride (NaCl) [table salt], barium
chloride (BaCl2)
Mixtures
• Two or more pure substances can combine to form
mixtures.
– mixtures:
• consist of many compounds and/or elements,
with no specific formula
• matter having variable composition with
definite or varying properties can be separated
into component elements and/or compounds
• Examples: Any alloy like brass, steel, 10-K to 18-K
gold (anything less than 24K gold); course mixtures
like sea water, carbonated soda; air is a mixture
consisting of nitrogen (~78%), oxygen (21%), and
other trace gases.
Mixtures
• Mixtures can be homogeneous or
heterogeneous:
– Homogeneous mixtures have a uniform
appearance and composition.
• e.g. solutions (salt water, soda, etc.),
metallic alloys, homogenized milk
– Heterogeneous mixtures do not have a
uniform composition
• e.g. chocolate chip cookie, coarse
mixture of sand and iron filings, raw
(non-homogenized) milk
1.6 States of Matter
• Matter exists in one of three physical states: solid,
liquid, gas
– Example 1: A few drops of food coloring is added to
a beaker of water. How would you expect the water
to appear after a few minutes? Why?
– Example 2: If you add a drop of food coloring on
top of an ice cube, would you expect the same
result? Why?
To understand matter, we must
recognize how particles behave at the
molecular level.
States of Matter
Gas
• Volume is variable, particles are
widely spaced
• Takes the shape of the container
because particles are moving
– If container volume expands,
particles move apart to fill
container
– If container volume decreases,
particles move closer together
• Particles are in constant random
motion
Liquid
• Fixed (or constant) volume, but
shape can change
• Takes the shape of the container
because particles are moving
• Particles are packed closely
together but move around each
other
Solid
• Has definite shape, rigid volume
• Particles can only vibrate in place
Changes of State
Gas
Condensation
Deposition
Sublimation
Vaporization
Liquid
Freezing
Melting
Solid
Properties of Matter
• Intensive Properties: properties independent of
quantity
– Density
– Boiling point
– Freezing point
• Extensive Properties: properties that depend on
quantity
– Mass
– Volume
Physical and Chemical
Properties and Changes
• Physical Properties:
– physical state (solid, liquid, gas)
– electrical and heat conductivity
– color
– solubility (amount of solid that dissolves in liquid)
– density
– hardness
– melting and boiling points
– odor
• Chemical Properties: how a substance reacts with other
substances
– e.g. hydrogen reacts explosively with oxygen
Chemical vs. Physical Changes
Physical Change:
• a process that does not alter the chemical makeup of
the starting materials
– changing shape, changing physical state, dissolving
– boiling water, melting ice, hammering gold into foil,
dissolving salt in water
Note: In the images here, the
chemical makeup of H2O
does not change as it goes
from a solid to a liquid and
to a gas.
Chemical vs. Physical Changes
Chemical Change:
• a process that does changes the chemical makeup of
the starting materials
• We can use space-filling models to show what
happens at the molecular-level when H2 and O2 react
to form water (H2O) of each molecule.
Notice that the H2O has a different chemical makeup
than H2 and O2.
Chemical vs. Physical Changes
The following examples are all chemical changes that
convert the reactants to completely different
compounds and/or elements.
release of gas
bubbles
(fizzing)
formation of
insoluble solid
(precipitation)
oxidation of matter
(burning or rusting)
Example Problem 1
Consider the following molecular-level representations of
different substances:
A
B
C
E
D
F
For each figure above, indicate if it represents an element, a compound, or a
mixture AND if it represents a solid, liquid, or gas.
Example Problem 2
Match the following substances with the correct molecular-level
representation.
A
B
C
E
D
_____ ammonia (NH3)
_____ sodium chloride
F
_____ air
_____ mercury
_____ hydrogen
_____ copper
Example Problem 3
Which of the following are chemical changes?
burning
condensing
dissolving
melting
vaporizing
rusting
Making Measurements and
Expressing Results
Accuracy vs. Precision
• accuracy: indicates how close a measurement is to
the true value
• precision: refers to how closely two or more
measurements agree with one another
For each diagram (above), what is the level of accuracy and precision?
accurate
inaccurate
precise
imprecise
Testing a Hypothesis – The Big
Bang Revisited
• In the 1960s, the US launched the first communication
satellites, called Echo and Telstar, which were basically
reflective spheres that bounced microwave signals from
transmitters to receivers back on Earth.
• Bell Labs in NJ had built an antenna to receive such signals,
and two Bell Lab scientists, Robert W. Wilson and Arno A.
Penzias, were trying to improve the antenna’s reception.
• But they kept picking up a background
signal, no matter where they directed
the antenna.
Testing a Hypothesis – The Big
Bang Revisited
• Assuming the signal was just an
artifact, even attributing it to pigeons
roosting on the antenna, the pair
continued testing the equipment until
they finally realized their original
hypothesis must have been wrong,
that the nuisance signal was not an
artifact but actually significant.
Testing a Hypothesis – The Big
Bang Revisited
• Wilson and Penzias learned that a Princeton
University physicist named Robert Dicke had
predicted residual energy left over from the Big Bang.
• Their nuisance signal matched Professor Dicke’s
predicted Big Bang microwave echo  Wilson and
Penzias shared the Nobel Prize in Physics in 1978 for
discovering the cosmic microwave background
radiation of the universe.