Matter and Mixtures
All of our physical world is made of matter. Matter is
anything that occupies space and has mass. Over time, we
have developed the idea that every large lump of matter is
made out of tiny particles invisible to the human eye. The idea
that matter is is called the particle theory of matter. The
particle theory states that…
all matter is made from particles,
different particles have different properties,
particles are constantly in motion.
1
We can classify matter into 3 broad categories called states of
matter—solids, liquids, and gasses.
A solid has a definite shape and volume.
A liquid has a definite volume but no definite shape.
A gas has neither a definite volume or shape.
Gas
Liquid
Solid
2
There are attractive forces between particles.
In a solid, the attraction between particles is
strong so the matter holds its shape. The
particles are still moving, but they are not able
to slide past each other. They just vibrate.
In a liquid the attractive forces are not as
strong. The particles are able to move past
each other and slide around. The forces are
strong enough to keep the particles from flying
away.
In a gas, the attraction between particles is so
weak that they fly in every direction filling the
container that they are held.
3
As a solid is heated, the particles begin to move more
quickly. The attraction between them is reduced and they
begin to slide past each other. This is called melting.
If heating is continued, the particles gain even more
energy and begin to fly away from each other in all
directions. This is called vaporization.
4
The reverse process can happen as well.
A gas can be cooled so that the particles
loose energy. The attractive force pulls
them together making a liquid. This is
called condensation. Dew on leaves in
the morning is an example of
condensation.
If cooling continues, eventually
the particles slow down enough
that they are strongly attracted to
each other. This is called freezing
or solidification. Ice form is an
example of the solidification of
water.
5
Dry ice is called “dry” because when it heats up, it does
not make a liquid. Instead the particles jump very
energetically so that a gas is formed without a liquid. This
is called sublimation. The reverse process is necessary to
make dry ice from carbon dioxide gas. When a gas
changes directly to a solid, the process is also called
sublimation.
6
solidification (freezing)
melting
7
As well as classifying matter as solids, liquids, and gasses, we
can classify matter as either a mixture or a pure substance.
A pure substance is made from only one type of particle.
These specific particle types give the substance its physical
characteristics such as odor, color, hardness.
A mixture contains two or more substances.
A homogeneous mixture has two
substances where the particles are
blended completely. To the eye, the
mixture appears to be pure substance.
When the particles stay intermixed and
don’t settle into layers we call the
homogeneous mixture a solution.
8
A heterogeneous mixture has large
clumps of particles that don’t fully
separate and get intermixed with
the other substance.
Some mixtures are in-between homogeneous solutions and
heterogeneous mixtures. A suspension has clumps that stay
floating. Filtering a suspension will usually separate the
particles.
A colloid has very small clumps that almost make a solution.
The clumps are so small that they pass through most filters.
Milk is an example of a colloid. The clumps of particles can
even be held separate with an emulsifying agent. When such
an agent is used, an emulsion is created (like mayonnaise).
9
A mixture that is obviously heterogeneous is called a
mechanical mixture. A mechanical mixture has separate
parts called phases. These phases can be separated into
layers that are distinct and visible. Oil forming layers in
water is another mechanical mixture with visible phases.
10
When we put sugar into water, a homogeneous mixture results.
The sugar particles are completely separated from the clumps
of other sugar particles. This process is called dissolving. The
attractive forces between the sugar particles and the water
particles is strong enough to pull the sugar particles away from
the main clump.
In fact, when water vaporizes, the water
particles are being dissolved into the air.
11
This pill is being dissolved in water. The pill
is called the solute because it is the substance
being dissolved. The water is called the
solvent because it is the substance that is
doing the dissolving. In general, the solvent
is in much higher quantity than the solute.
Another way to say that the pill dissolves in water is to say
that the pill is soluble in water. If a particular solute is soluble
in a solvent, that means that the solute will dissolve in the
solvent and make a homogeneous solution. For example, nail
polish does not dissolve in water, but if we use a different
solvent like acetone (nail polish remover) the polish does
dissolve.
12
On Earth, water is the most common solvent. Most animals
and plants need water to dissolve nutrients to help carry them
through the body. Our blood is over half water. Water will
dissolve anything given enough time.
So, why don’t we dissolve away from the water in our own
bodies?
The rate of dissolving for many substances is very slow.
Even rocks will dissolve in water if given a few million
years. We can speed up the process of dissolving by
agitation (mixing) or by heating the solvent. Both agitation
and heating will increase the speed of the solvents particles
and allow them to break up the solute faster.
13
According to the particle theory, every pure substance is made
from different particles with different properties. This means
that some particles have a strong attraction with each other and
different particles may have weak attractions. This means that
some substances are more soluble in different solvents that
others because their particles break away more easily.
Substance
Solubility (g/100g of water at 0°C)
Baking soda
6.9
Canola oil
Insoluble
Ethyl alcohol
Unlimited
Limestone
Oxygen
0.0007
0.007
Salt
35.7
Sugar
179.2
14
When a particular solvent has
dissolved as much solute as possible,
the homogeneous mixture is called
saturated. A saturated solution will
still have some visible solid not yet
dissolved.
If the solvent can still dissolve
more solute, the solution is said to
be unsaturated. The point of
saturation will define the solubility
of the solute in the solvent. It is
possible to go beyond the
saturation point.
15
A heated solvent will dissolve more solute than a cool solvent.
If a heated solvent is saturated and then slowly left to cool, the
amount of solute in the cool solvent is beyond to saturation
point. The mixture is said to be supersaturated. With any
small disturbance, like adding a small piece of solid solute,
crystals of solute will form. This is called crystallization.
16
The fact that solvents have different solubilities with different
solutes is very helpful to us. When we get a stain on our
clothes, the stain is usually insoluble in water. By using a
detergent, the particles of the stain can be removed. The
difficulty is that often a solvent that removes the stain will also
remove the pigment that gives your clothes their color.
Therefore, the trick is try to find a detergent that dissolves the
stain but not the pigment.
Restoring artwork is particularly
difficult. Oils and dirt over time
collect on the oil painting. It is
difficult to remove only the dirty oil
and leave behind the paint. The left
side of this painting has been cleaned.
17
Separating mechanical mixtures is usually quite simple. Most
of us can usually pick out the cashews from a bowl of mixed
nuts and gravy separators can easily skim off oil.
Suspensions like coffee are easily
filtered to take out the tiny solid clumps
floating in the liquid.
18
Separating a homogeneous solution is much more difficult.
One of the most basic techniques of purifying water from
dissolved solutes is called distillation. During this process, a
homogeneous mixture is heated vaporizing some of the
solvent. The vapor rises and is then condensed in a special
tube called a condenser. The solvent becomes liquid again and
is recollected. The result is a pure substance.
Water in
Condenser
Water out
19
If necessary, solar energy can be used to evaporate water. The
vapor rises, hits a clear plastic sheet, condenses, and slides
along the edges to outside collection disks. A simpler design
uses a plastic wrap around a large container and a smaller
container inside. A small pebble leads the condensed water to
the center container.
20
Crude oil is separated into
different chemicals in a
process called fractional
distillation. The crude is
heated to about 400°C and
then allowed to pass through
a large column. Lighter
gases are collected at the top
while heavier liquids fall
further to the bottom. At
different locations, the
fractions are collected and
piped away.
21
Solid mixtures also require a great amount of work to
separate. This is iron ore. An ore is a rock contains a useful
substance, like iron or gold, and some other substances. To
separate the useful substance from the ore, first it is crushed
and then mixed with water to make a suspension. Chemicals
are added to dissolve the iron but not other chemicals. The
suspension is filtered. The pure iron can then be extracted
from the water using chemicals and distillation.
22
Fluid Properties
A fluid is any substance whose particles are able to slide past
each other. Liquids and gasses are fluids because their
particles flow easily past each other. One of the main
properties of a fluid is the speed that it flows. This is called
the fluid’s viscosity. A thick fluid, like ketchup, is more
viscous and flows more slowly than a thin fluid.
We measure viscosity by measuring the how
fast the fluid flows. This speed is called the
flow rate. Ketchup has a flow rate of about
40km per year when poured from a bottle.
23
The flow rate (and therefore viscosity) can be altered. For
example, if the fluid is heated, it flows more quickly and
hence has a lower viscosity. If it is cooled, it will flow much
more slowly and have a much higher viscosity. This can be
very useful to the creation and manufacture of many products
such as Caramilk™ bars. First chocolate is heated so it flows
more easily. Then it is poured into a mold. Caramel is heated
and poured into a similar smaller mold. The caramel is then
frozen solid. The little caramel nuggets are then put into the
soft chocolate and covered with more heated chocolate. The
whole thing is allowed to cool and popped out of the mold
when it is solid.
24
The reason why liquids flow faster when hot is easily
explained by the particle theory. As a fluid is heated, the
particles move more quickly. If the particles move more
quickly, they can more quickly slide past each other.
In exactly the same way, if a liquid is cooled, the particles
flow more slowly. This explains why a fluid that is cooled
will flow more slowly.
25
Different fluids have different viscosities. This is because the
particles in different fluids have different properties. Again,
this is part of the particle theory. Water particles are fairly
small and are able to slip past each other fairly easily. Heavy
oils like tar and petroleum jelly have much larger particles and
bump into each other more easily. This makes fluids with
larger particles have more internal friction between the
particles and decreases their ability to slide past each other.
water
tar
26
Gasses are fluids as well. When can see super cooled water
vapor flowing along the ground when we put dry ice into hot
water. This is a cloud, (just like the clouds in the sky) that
flows through the air.
However, gas particles move quite
differently than liquid particles. The
attractive forces between particles of a gas
is very low since the particles are so far
apart. They move very quickly in many
random directions.
27
Heating a gas will increase the speed of the particles however,
it will also increase the randomness of the particle direction.
This is a little different than a liquid.
Particles in a liquid for the most part stay close to each other,
so if some start moving one direction, most of the rest start
moving the same direction. This is important when looking at
flow rate and viscosity because the flow rate measures the
speed of the net movement of the particles.
Cool liquid
Hot liquid
28
To increase the flow rate of a gas, we need to try to make the
particles stay closer together so they flow the same direction.
By cooling a gas, we are able to keep the particles closer
together and increase the flow rate. This means that cooling a
gas decreases the viscosity. In the opposite way, heating a gas
makes the particle motion more random, decreases the flow
rate and thus increase viscosity.
Heating a Liquid
Flow Rate
Viscosity
Heating a Gas
Flow Rate
Viscosity
Cooling a Liquid
Flow Rate
Viscosity
Cooling a Gas
Flow Rate
Viscosity
29
Particles in a fluid are able to flow past each other. This
means that there is space between the particles. To measure
how crowded the particles of a fluid are, we measure density.
We cannot easily measure the space between the particles. But
we could take a particular volume of a substance and measure
its mass. This gives us a formula for density.
m
D
V
In the formula, “d” is the density, “m” is the mass in grams,
and “v” is the volume in cm3. We need to remember on more
thing. 1cm3 = 1mL
Because particles have different sizes and masses, different
substances will have different densities.
30
Solids tend to have the largest densities. This is because their
particles are so close together. In a fluid, like air, there is a
very low density. As a plane flies through the air, the gas
particles are pushed aside and solid metal glides through.
This is one of the reasons planes can fly
so fast—they travel through very thin
air.
Boats however travel through more
dense water. The water particles are
still pushed aside but it takes greater
effort. Even very powerful boats
cannot travel as fast as a plane.
31
Comparing densities can be difficult. Since water is so
plentiful and common, 1mL of water was assigned the mass of
1gram. Therefore, the density of water is 1g/mL. Compare
this to other substances.
Substance
Hydrogen
Helium
Air
Oxygen
Carbon Dioxide
Water
Seawater
Mercury
Density (g/mL)
0.000009
0.0002
0.0013
0.0014
0.002
1.00
1.03
13.55
Substance
Styrofoam™
Cork
Sugar
Salt
Aluminum
Iron
Lead
Gold
Density (g/mL)
0.005
0.24
1.59
2.16
2.70
7.87
11.34
19.32
32
Calculating density is much more difficult than you might
think. First we need to know the mass of an object. To
measure the mass, we need to use a balance. If we use a scale,
we measure the weight of the object. The weight is the force
due to gravity pulling down. The mass is measured by the
balance because the objects mass needs to counteract the
weights on the balance.
So we can use the weight of
the object on a balance to
measure the mass of the
object.
33
Measuring the volume of an object can be very tricky as well.
Most objects are not regular shapes that we have formulas for
to calculate the volume.
r
h
V  l  w h
4
V     r3
3
w
l
b2
r
h
V  r h
2
a
h
 b1  b2 
V  a
h
 2 
b1
34
But most real life objects only resemble these shapes. If we
want more accurate calculations we need to find the volume of
very odd shapes. Measuring the volume of an odd shaped
object is almost impossible by calculation. The displacement
method is an easy way to find the volume.
If the object sinks in water, we can
measure a volume of water, then
drop the object into the container.
The water level will rise because
the particles are displaced. The
difference in the water levels from
before and after will give you the
volume.
35
Not all objects will sink however. If they do, we can sink
them in fluids with a smaller density or push them down with
some object with a known volume.
The ability to keep an object floating is called buoyancy. An
object floats due to a buoyant force that works against gravity.
The existence of a buoyant force can be explained using the
particle theory. Particles in a fluid are still attracted to each
other. Pushing them aside requires some force. When an
object is sinking, gravity is providing the force downward.
The attractive forces between particles resist this force.
36
A dense fluid should resist more strongly and therefore
demonstrate a stronger buoyant force. This can actually be
seen using very dense fluids like mercury.
Mercury is an extremely dense
liquid metal. Iron, bricks, or
billiard balls float easily in
mercury. It is toxic however and
should not be handled.
Water is not nearly as dense as mercury. How is it then that
boats made from iron, steel, or aluminum are able to float?
37
Recall that there is a formula for the density.
m
D
V
Air has a very low density (almost 0). Therefore, if an object
is able to trap a large quantity of air then it should be able to
lower its density. If the average density of the object in the
water is less than 1, then the object should float. Look at the
cross section of a boat floating in water.
Large volume of air
trapped.
Dense hull
38
A submarine can alter the average density of the ship by
pumping water into large holding tanks called ballasts. To
make the submarine rise, the water is pumped out and air
pumped into the ballasts.
Fish use a swim bladder that
they fill with air to make
them float. They push the
air out to increase density
and sink.
39
The concept of buoyant force is not a new
one. Archimedes at around 200 BC
discovered that a sinking object will
disperse a volume of water equal to its own
volume. He theorized that this was why a
boat could float despite being filled with
heavy objects.
An object with a volume great enough to float its mass is said
to have neutral buoyancy. Archimedes summarized his
findings about buoyancy and came up with a way to calculate
the buoyant force. This is called Archimedes Principle—the
buoyant force acting on an object equals the weight of the
fluid displaced by the object.
40
A hydrometer is another way to measure
the density. This one measures the salinity
(amount of dissolved salts) in aquarium
water.
This hydrometer is used to test the quality
of a car’s antifreeze. Antifreeze that has
degraded due to heat and age will be less
dense and less able to keep the car from
freezing or overheating.
41
Fluids Systems and Pressure
When you exert a force against an object you are applying
pressure to the object. Pressure is the amount of force applied
divided by the area that the force is applied over. We use the
following formula to relate the pressure (P) to the force (F)
and the area (A).
F
P
A
The unit of pressure is called a pascal (Pa) named after the
scientist Blaise Pascal. 1 pascal is equal to the 1 Newton of
force exerted over an area of 1 m2. This is about the weight of
a small apple spread over a 1 m2 area. This is very small so
we usually use the kilopascal (kPa) to measure pressure.
42
If a gas is enclosed in a container, a force
can be applied to the gas. This causes
compression of the gas. The particles are
forced into a smaller volume reducing the
spaces between the particles.
The force exerted is needed to compress
the spaces between the particles. Since
gasses have a large amount of space
between particles, they are able to absorb a
lot of force and compress very
significantly. Liquids and solids do not
compress very well
43
We use compression of gasses
every day. This high jump mat is
full of air and cushions your fall
when you land after your jump.
An air bag absorbs the force of your
body impacting and slows you down
more safely in high speed car crashes.
44
The atmosphere of the Earth is actually quite thick (~160km).
Gravity keeps the atmosphere close to the surface. The weight
of the air exerts pressure on all of the objects on the ground.
In the same way that we can feel the difference in pressure as
we dive deeper into a pool of water, the air pressure increases
as you get closer to sea level. The reason we don’t get crushed
from the pressure of the atmosphere is that we have an equal
pressure inside of us pushing outward. Moving suddenly from
one altitude to another causes pressure differences.
Our ears popping is one effect of
pressure differences between the
atmosphere and inside our
bodies.
45
This mercury barometer
measures the atmospheric
pressure. The large pool of
mercury experiences
pressure from the
atmosphere. The liquid is
forced up the vacuum tube
against the force of gravity.
The height of the mercury
in the tube is then
measured. Normal
atmospheric pressure
pushes the mercury to a
height of 760 mm.
46
Pressure can be stored in a container and released at controlled
times when we want to exert a force. A can of whipped cream
is an aerosol. It contains a gas under pressure that when
released through the nozzle, pushes and cream out. Aerosol
products are common in cleaners, hair mousse, and spray
paint. Chlorofluorohydrocarbons (CFC’s) uses to be used as
the gas under pressure because these compounds are very nonreactive.
It was found later that CFC can react in the
upper atmosphere and causes breakdowns in the
Ozone layer protecting Earth from UV
radiation.
47
It is possible to use pressure inside a closed
system. An air pump, for example, compresses
air and sends it through a nozzle using a set of
valves to control the direction of the flowing air
particles.
As the plunger is pushed down, air inside
the container is compressed. The valve at
the bottom is open and allows air to be
pushed through the nozzle. When the
plunger is pulled up, the valve at the bottom
shuts and the top valve opens allowing the
atmospheric pressure to push air back into
the pump.
48
Liquids can also be made to flow in systems. In many ways,
liquids are more useful than gasses since they do not compress
as much as gasses. Your car uses a liquid oil in the brake
system to stop the car. When pressure is applied to the peddle,
the force is transferred to the brakes on the wheels.
Image what would happen if the brakes were filled with a gas
instead of a liquid. First the gas would need to be compressed
significantly and then the pressure would be transferred to the
brake pads. This would make your brakes less responsive and
would decrease the stopping power of your car.
49
A fluid system using pressure from liquids is called a
hydraulic. A hydraulic system uses the relationship of force
pressure and area. For example, this hydraulic has two
connected plungers with different areas. If a force is applied
to the small plunger, pressure is created throughout the system.
The area of the large plunger is much greater, therefore, the
force is much greater. This is because the pressure in the
system is constant.
50
Imagine this example. The area of the left plunger is 1m2 and
the area of the right plunger is 4m2. Then if 10N of force is
applied to the left plunger the pressure is found using our
formula.
F
Therefore, the pressure on the right side is
P
A
also 10Pa. We find the force up on the
10 N right side using the same formula again
P
2
1m but this time we know the pressure and the
P  10Pa area is larger.
F
P
A
F
10Pa
4m2
40N  F
51
This type of hydraulic system can be very useful when we are
trying to lift heavy loads. Pressure in hydraulics like refinery
pipes move liquids from one location to another. Pumps are
required to make enough pressure to move the fluids through.
Water slides also use hydraulics to move
water to the top of the slide. Gravity
pulls the water, and you, back down.
52
Liquids are not the only fluids moved in pipes. Natural gas is
also pushed using special pumps called compressors through
pipes in the ground to your home. A meter monitors how
much gas runs into the house and used. A gas system is called
a pneumatic system. A balloon can be though of as a
pneumatic system.
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