UNIT 2 – MATTER
CH1030
Mark Stacey
DEFINING MATTER
Our modern definition of matter is anything that has mass and takes
up space. We recognize that nearly everything in existence is made
from a common set of extremely-small building blocks. All matter is
effectively variants on the same system. This system is supported by
evidence that needs very complicated technology to obtain.
Therefore, it is not surprising that people had developed alternate
ideas prior to modern technology.
Over the history of chemistry, there have been many ideas about what
comprises the world we live in and how those “elements” interact.
DEFINING MATTER
One of the oldest systems to define matter was the ancient Chinese
system of yin and yang. This concept incorporates the idea of two
interconnected and complementary forces or states of being. This idea
existed mostly as a quasi-religious philosophy, but was also used to
describe the natural world.
Under this system, yin incorporated all things dark, cold and wet while
yang incorporated all things light, warm and dry. Different materials
were made of different combinations of these two forces.
Even under this basic system, the basic acknowledgement that all
matter comes from a combination of basic sources was evident.
DEFINING MATTER
A number of years later, the classical Greek concept of the four
elements came to prominence. Again in this system, all matter is
derived from a combination of base elements, however there are now
four: earth, wind, water and fire.
The four elements explain chemical changes by stating that matter
could change from one combination of elements to another. For
example, wood was said to be made of earth and fire. When wood
was burnt, it converted more completely into the fire element.
While primitive, this system introduces the idea that when chemical
reactions take place, the component elements are changed, and idea
that we still somewhat use today.
DEFINING MATTER
Another important concept introduced in the Greek era was that of
atoms – that matter was ultimately made of small indivisible particles.
You could divide and divide a material over and over, but eventually
you would reach a point where you would reach the irreducible
particle that is the atom.
Our understanding of what an atom is and how they work has
significantly improved and changed over the years, but it is an
important basic concept.
DEFINING MATTER
The precursor to modern chemistry was alchemy. In fact, many people
we hold up as famous early chemists would have identified as
alchemists in their day. In fact, the distinction between alchemy and
chemistry is not very distinct in some ways. There is much overlapping
the two.
Alchemists would expand on the four elements concept – identifying
more and more base elements. This was the beginning of what is now
our modern periodic table of elements. Our knowledge of elements
became so profound that we were able to predict the existence of
elements that we had not yet isolated.
As technology improved, the instruments alchemists used to study
matter improved, allowing breakthroughs in our understanding of
chemical proportions and physical properties.
DEFINING MATTER
A major difference in modern chemistry and prior systems is the
acceptance that all matter is from a common source.
While other systems had basic elements, there was usually some
“other” element separate from the rest that had life-giving, divine, or
magical properties. This came in many forms – concepts such as ether
and phlogiston which were “special” elements that were different from
the rest.
Along with these special elements, many previous systems had partial
or full religious elements to them. This is particularly true when
describing the difference in alchemy and modern chemistry.
DEFINING MATTER
The modern discipline of (Western) chemistry traces its earliest roots to
the Greeks. After the fall of Rome and the Dark Ages in Europe,
chemistry was preserved and improved by Arab scientists for many
centuries. Finally, in the Enlightenment era of Europe, many of the
classic Greek and subsequent Arab works were rediscovered and reintroduced, starting the practice of alchemy that would eventually spin
off modern chemistry. Since that time (17th century), modern chemistry
has grown significantly as our technology has drastically improved.
The late 19th and early-mid 20th century in particular saw fantastic
leaps in our chemistry knowledge.
MOLECULAR THEORY
One of the most important chemical theories of modern chemistry is
that of molecular theory.
This is an derivative of the idea of atoms from ancient Greeks.
In this theory, all matter is made ultimately of irreducible particles
called molecules. A molecule is the smallest piece of a substance that
still retains the properties of that substance. So even if you could
further break down a molecule, the new remnants would be molecules
of some other substance.
MOLECULAR THEORY
Water has the chemical formula
H2O, meaning a single molecule
of water is two hydrogen and
one oxygen bonded together.
A single “H2O” is as small as a
piece of water can be. If you
break the bonds of that H2O
molecule into lone H and O
pieces, you get hydrogen gas
and oxygen gas – not water.
MOLECULAR THEORY
Molecular theory states that a molecule can be made of one or more
base elements. Water is a compound, a combination of two or more
types of elements.
Again, water (a compound of hydrogen and oxygen) has a different
molecular makeup than lone oxygen and lone hydrogen.
MOLECULAR THEORY
A molecule is the
smallest particle of
any chemical – be it
a lone element,
multiples of a single
element, or a
combination of two
or more elements.
STATES OF MATTER
Matter exists mostly in three main states: solid, liquid and gas. Each of
these states is a result of the component molecules being in different
configurations.
Each state of matter is a result of the molecules having different
amounts of energy. Molecules are always in constant motion, but as
temperature increases, their movement increases more and more.
This is known as kinetic molecular theory – that the state of matter
that a chemical exists at is a function of its kinetic state, that is, its
motion.
STATES OF MATTER
Solids, liquids and gases of a chemical are all made of the same
molecules, just operating a different speeds. With more kinetic energy,
the molecules are able to move more freely. This is why solids are
very immobile – they lack the energy for the molecules to move away
from each other. Comparatively, gasses have enough energy to move
around rapidly and expand to fill their container.
STATES OF MATTER
Solids contain the lowest amount of energy of all the states of matter.
Solids usually are also the most densely-packed form of a chemical. In
most chemicals, the slowly-moving molecules pull tightly together and hold
onto one another relatively strongly.
While solids generally feel completely stationary, the molecules are still
moving on some level. Only at the coldest temperature possible, absolute
zero (-273.15 °C), does molecular motion completely cease.
As their molecules lack the energy to move significantly, solids have a
fixed shape and fixed volume. Some solids may show some very, very
minor degree of compressibility (crushing them to make them take up less
volume), but this is usually just the effect of removing empty space pockets
amongst the molecules and not actually forcing them closer together at
the molecular level.
STATES OF MATTER
Liquids exists at the next energy level of matter. These molecules have
more energy than their solid counterparts, but less than gases.
Liquid molecules are much more free to move around and have more
energy to enable them to do so. This allows liquids to have an unfixed
shape, they bend and flow to fit their container. However, the
molecules do not have the needed energy to break their attraction to
one another, and so they stay at a fixed volume.
Liquids are usually less dense than their solid forms as the molecules
have spread out more. Like solids, liquids are generally not
significantly compressible either. This fact is taken advantage of in
hydraulic equipment.
STATES OF MATTER
Gases represent the highest-energy state for most matter.
At this point, the molecules have so much energy that they have
overcome a large percentage of their attraction to one another –
meaning that the molecules are free to spread out as they like. This is
why gases do not have a fixed shape or volume.
Gases are much less dense than liquids or solids. However, unlike
solids or liquids, gases can vary in their density – they are
compressible. There is a limit to compressibility however, if you
compress a gas too far, it will transform into the liquid phase.
Similarly, liquids can be compressed into the solid phase if enough
pressure is added.
STATES OF MATTER
STATES OF MATTER
There is a fourth state of matter known as plasma. While very little
matter on Earth exists as plasma, the majority of matter in the universe
elsewhere is in the plasma state.
Plasmas are created from even higher levels of energy than that of
gases. As such, most plasmas are the result of the immense forces in
stars. Plasmas can also be created at more reasonable temperatures
using electrical or magnetic forces (neon lamps).
Plasmas not only have the molecules at very high energy like gases,
but at such as high level that the positive and negative components of
the molecules begin to separate.
STATES OF MATTER
All elements can exist in any of the four states of matter. Life on Earth
exists within a very small range of temperatures, and thus we often only
see some chemicals in one state.
For example, helium on Earth is generally in the form of a gas. However,
if lowered to -268.9 °C helium will condense into a liquid. If taken further
to -272.2 °C, helium freezes solid.
By the same logic, something like iron, which is normally a solid on Earth,
can be melted at 1538 °C, and then turned into a gas at 2862 °C.
Plasma can be made from all elements too. Temperatures needed to
convert to plasma vary, as electromagnetic forces can contribute to the
formation as well. However, to create plasma of water by temperature
alone would take temperatures of over 11000 °C, compared to only 100
°C to convert to the gas phase.
STATES OF MATTER
While we often state that it is theoretically possible for any chemical
to exist as any state of matter, actually achieving this is quite difficult.
Many compounds will undergo chemical reactions, changing their
molecular makeup if their temperature is radically changed.
For example, many compounds decompose, burn, or explode at high
temperatures. This is not a phase change as the makeup of the
molecules involved has changed (gasoline has different molecules than
exhaust fumes).
TRIPLE POINT
The state of matter is a function of
temperature and pressure.
For many chemicals, there is actually a
specific point where all three states of
matter are possible – the triple point.
Chemicals at this point can be seen to
rapidly shift between all of the phases
back and forth as the conditions
change.
STATES OF MATTER - WATER
Even though water is one of the most common and most important
chemicals for living things, it is actually is one of the few exceptions to
some of the general rules regarding the states of matter.
Specifically, solid water (ice) is less dense than liquid water.
Water molecules are shaped and charged in such a way that when
they are moving about with higher energy (liquid) they can move quite
close to one another. However, once they reduce to lower energy, their
charges make them align into a crystal pattern. This pattern spaces
the molecules farther apart than the molecules would normally be as a
liquid.
STATES OF MATTER - WATER
The fact that ice is less dense than water is very beneficial to life on
Earth. It means that ice floats on water, rather than forming on the
bottom. If ice formed on the bottom first, all life on the sea floor
would be destroyed every winter. In comparison, ice on top of the
water creates much fewer problems for living things.
HEAT
Heat is another term that is often used in various contexts in everyday
usage but has a very specific definition in chemistry.
Heat is the transfer of energy from one object to another without
applying a force (such as motion). Heat is always passed from warmer
things to cooler things.
The energy transferred by heat (or energy transferred by any other
means) is officially measured in Joules (J).
HEAT
Another useful unit to measure heat is the calorie (cal). One calorie is
equal to the amount of energy needed to raise 1 gram of water by
one degree Celsius (1 cal = 4.185 J).
In everyday life, we often use the term “calorie” as a measure of
energy in food. It should be noted that the “calories” seen on food
packaging are kilocalories (kcal), which are usually written as
“Calories (Cal)” (with a capital C). One kilocalorie is equal to 1000
calories (therefore 1000 cal = 1kcal = 1 Cal = 4185 J = 4.185 kJ)
PHASE CHANGES
Adding or removing sufficient heat to a chemical will cause it to
change from state of matter to another. This is called a phase change.
Phase changes can occur from any of the three traditional states of
matter to any other. They are also reversible reactions (simply return
to the original temperature).
Generally, plasmas are only formed from the gas phase. A liquid
converting to a plasma will become a gas on its way to becoming a
plasma.
PHASE CHANGES
This is because most chemicals
are slowly exposed to heat and
as such have time to convert to a
liquid first.
Increasing Energy
In everyday life, we generally do
not observe many cases of solids
converting directly to gases or
vice versa.
For example, an ice cube in a
frying pan will have heat added
to it slowly enough that it will
generally melt into water first
before becoming steam.
However, if an ice cube were
placed in a 1000+ degree
furnace, it would undergo
sublimation – converting straight
from solid to gas as it receives so
much heat so quickly.
Increasing Energy
PHASE CHANGES
PHASE CHANGES
Phase changes can be grouped into two major categories, depending
on if they involve heat entering or leaving the system.
Phase changes that add heat to the system are endothermic
processes. This means that energy is added inside the system (endo =
inner).
Phase changes that remove heat away from the system are
exothermic processes. This means that energy is lost to outside of the
system (exo = outside).
PHASE CHANGES
Endothermic Processes:




Sublimation (solid to gas)
Melting (also called fusion) (solid to liquid)
Vaporization* (liquid to gas)
Ionization (gas to plasma)
Exothermic Processes:




Deposition (gas to solid)
Freezing (liquid to solid)
Condensation (gas to liquid)
Recombination (plasma to gas)
*Vaporization can be used to
describe both the processes
of evaporation and boiling,
which on a technical level are
different processes.
For the scope of this course,
we will treat vaporization,
evaporation and boiling as
interchangeable terms.
PHASE CHANGES
While all chemicals can exist in all states, every chemical undergoes
phase changes at different temperatures.
There are two major reasons for this – differing masses, and differing
levels of molecule-to-molecule attraction.
The state of matter is dependent on its kinetic energy. It takes more
work (more energy applied) to make heavier things move than lighter
things. This is why the lightest molecules have very low melting/boiling
points (hydrogen melts at -259.2 °C) while heavier molecules have
much higher melting/boiling points (iron melts at 1538 °C).
PHASE CHANGES
All molecules show some degree of attraction to one another.
However, some chemicals can form much stronger attractions between
its molecules.
In order for an endothermic phase change to occur, the molecules must
generally spread out and become less dense. In order for this to
happen, the attraction the molecules have to one another must be
(partially) overcome.
Therefore, any molecule that has strong intermolecular attraction will
require more energy to separate, and thus more energy to convert
from one phase to another. In turn, this means a higher melting/boiling
point.
PHASE CHANGES
Energy needed for phase changes:
Mass
 Heavier molecules are harder to move and thus take more energy (higher
temperatures) to phase change.
 Lighter molecules are harder to move and thus take less energy (lower
temperatures) to phase change.
Intermolecular Attraction
 Strongly inter-attracted molecules take more energy (higher temperatures) to phase
change.
 Loosely inter-attracted molecules takes less energy (lower temperatures) to phase
change.
PROPERTIES OF MATTER
While solids, liquids, gases, and plasmas each have certain consistent
traits, each and every individual chemical has its own set of
properties. Properties include appearance, physical strength,
reactivity, etc. Properties come in two major categories:
Physical Properties are traits that can be directly observed by this
one chemical alone. This includes color, structure, shine/lustre,
malleability (ability to be bent/re-shapen), melting/boiling/ionization
points, hardness/brittleness, density, texture, etc.
Chemical Properties describe how a chemical interacts with other
chemicals. This includes what types of chemicals it reacts with, the
vigor and speed of these reactions, the energy needed/yielded from
these reactions, etc.
PROPERTIES OF MATTER
Here are the properties of some
common and important chemicals:
Hydrogen
 Physical Properties:
 Gas at room temperature
 Clear, colorless
 Odorless
 Lightest element
 Smallest molecule of any element
 Chemical Properties:
 will violently burn with oxygen
 Explosive
 When on its own, will generally bond into pairs forming
a H2 molecule.
Hydrogen is the most abundant
element in the universe
(~75%), mostly existing in the
form of plasma.
PROPERTIES OF MATTER
Oxygen
 Physical Properties:
 Gas at room temperature
 Clear, colorless
 Odorless
 Significantly heavier than hydrogen (~16 times heavier)
 Chemical Properties:
 Reactive with a very broad assortment of chemicals
 Used in most burning/explosive/combustion reactions
 Powerful oxidant (a type of chemical that takes
electrons from other chemicals)
 Reacts with food molecules to release energy in many
living things
 A major ingredient in the majority of rocks on Earth
 When on its own, will generally bond into pairs forming
a O2 molecule.
Oxygen makes up only ~20%
of the air we breathe. People
having difficulty breathing are
often given 100% oxygen.
PROPERTIES OF MATTER
Water (Dihydrogen monoxide)
 A compound of hydrogen and oxygen (H2O)
 Physical Properties:
 Liquid at room temperature, although all 3 forms
appear on Earth
 Clear. Appears colorless to the naked eye at short
distances, begins to take on color in larger amounts.
 Perfectly pure water is odorless and tasteless
 Due to an uneven charge distribution on the molecule,
can form into intermolecular crystals (in particular, ones
that result in the solid phase being less dense than the
liquid.)
 Chemical Properties:
 Extremely good solvent (good at dissolving up other
chemicals)
 Decomposes into hydrogen and oxygen when exposed
to electrolysis.
 Will violently react with certain metals
Water is essential for life as
we know it. Water makes up a
large percentage of the cells
of all living things.
PROPERTIES OF MATTER
Carbon
Physical Properties:
 Solid at room temperature
 Can exist in several solid forms depending on how the
individual molecules are interacting – from soft, flaky
graphite dust, to extremely hard, rocky diamond.
 Chemical Properties:
 Not very reactive in its standalone form, but is capable
of making many, many, many different compounds.
 Has a unique bonding ability that allows it to form
complex molecule shapes such as chains, loops, and
rings.
 Is the “backbone” chemical for most biological
molecules (proteins, fats, carbs)
Life on Earth can be said to be
“carbon-based life” as carbon
is a vital component of all of
the major biological molecules.
PROPERTIES OF MATTER
Carbon Dioxide
 A compound of carbon and oxygen (CO2)
 Physical Properties:
 Gas at room temperature
 Clear, colorless
 Odorless
 CO2 in the air helps redirect heat leaving the Earth
back towards the Earth, helping it retain heat better.
This is known as being a greenhouse gas, and is a major
factor in the changes in climate over the years.
 Chemical Properties:
 Rather unreactive
 Dissolves in water relatively easily (carbonation)
 Dissolved carbon dioxide can act as an acid-base
buffer (carbonate)
 Common product of burning/combustion reactions
PROPERTIES OF MATTER
Carbon Dioxide
 Another carbon-oxygen compound, this time with one
atom of each (CO)
 Physical Properties:
 Gas at room temperature
 Clear, colorless
 Odorless
 Physically sized rather similar to an O2 molecule
 Chemical Properties:
 Similar to carbon dioxide in that it is generally
unreactive
 Like carbon dioxide, it is a common product of
burning/combustion reactions – although little to no
carbon monoxide is made under more ideal conditions.
Carbon monoxide is extremely
dangerous. It replaces oxygen
in your bloodstream, depriving
your body’s tissues of oxygen,
resulting in cell damage and
ultimately death.
CHANGES OF MATTER
Chemicals rarely stay in one form forever. Chemicals undergo
changes where they are converted into a new form. These changes
come in two main varieties:
A physical change involves a chemical converting to another form of
itself, but its own molecular makeup does not change. Phase changes
are an example of physical changes. Any sort of bending, breaking,
molding or other reshaping of a chemical is usually a physical change.
Physical changes are also generally reversible – meaning that it is
simple to convert back to the original form (such as re-freezing a
melted ice cube). As long as the chemical formula for the chemical
doesn’t change, it is a physical change (ice is H2O and liquid water is
also H2O).
CHANGES OF MATTER
Chemical changes, on the other hand, involve the molecules of
chemicals changing. As the chemical formula changes, the beginning
and final chemicals are different (gasoline contains C8H18, exhaust
fumes contain CO2).
Many chemical changes are not easily reversed. Smoke and fire
cannot be converted back into wood, for example. Some chemical
changes can be reversed with enough added energy, such as
recharging a battery.
CHANGES OF MATTER
CHANGES OF MATTER
Some processes involve both a
physical and chemical change.
For example, when sugar is
heated, it will convert into a
liquid (physical change) but as
the heating continues, it will
chemically change as well, going
from simple sugars such as
sucrose to complex carbohydrate
polymers (caramel), and then
eventually burning into char and
ash if overheated (chemical
changes).
MIXTURES AND PURE SUBSTANCES
A pure substance has only one kind of molecule. These molecules can be
made up of two or more different elements, but the whole molecules
themselves must be identical.
If a pure substance contains only one kind of chemical in its molecules, we
call it an element.
Examples:
 A bar of 100% gold (gold molecules contain only gold)
 A tank of 100% oxygen (oxygen molecules contain only oxygen)
If a pure substance contains only two or more elements in its molecules, we
call it a compound.
Examples:
 A bottle of 100% water (water molecules contain oxygen and hydrogen)
 A jar or 100% sucrose (sucrose molecules contain carbon, oxygen and hydrogen)
MIXTURES AND PURE SUBSTANCES
However, most chemicals do not exist as perfectly pure substances.
Most chemicals exist in combination with others in a mixture. Mixtures
contain two or more distinct types of molecules.
Heterogeneous mixtures have two or more separate parts visible
(hetero = different). Oil and water mixed together will show a distinct
oil and water layer, for example.
Homogeneous mixtures have one singular appearance (homo =
same). Salt water appears as one continuous liquid, with no separate
water and salt portions visible.
MIXTURES AND PURE SUBSTANCES