Phases (States) of Matter
Matter is defined as anything that has mass and
There are 4 states of matter
• Solids, Liquids, Gases and Plasmas
Most of the matter on the Earth is in the form of
the first 3 whereas most of the matter in the
Universe is in the plasma state.
• Macroscopic properties are all the observable
behaviours of that material such as shape,
• The many macroscopic or physical properties
of a substance can provide evidence for the
nature of that substance.
Characteristics Solid Liquid Gas
Characteristics Solid Liquid Gas
Shape Definite Variable Variable
Volume Definite Definite Variable
Diffusion Small Slow Fast
High High Low
At the atomic level we consider the energy of the
The energy is in the form of:
• Kinetic Energy, KE
• Potential Energy, PE
Characteristics Solid Liquid Gas
PE High Higher Highest
Describe the Energy in…
1. Water running from a tap
2. Air in a room
3. Coffee in a cup
Before the turn of the previous century it was
thought that the content of a solid,determined its
It was what made diamonds hard, lead heavy
and iron magnetic.
The characteristics of a solid are due to its
structure. That is, the arrangement of atoms
within the material.
To keep the atoms in the regular pattern (lattice)
there are forces (electrical in nature) which bind
If the atoms get too close, the force becomes
repulsive (between electrons in their outer shells).
In solids, the thermal energy is very much smaller
than the intermolecular binding energy and so,
solids have specific macroscopic properties.
Solids maintain a fixed shape and, a fixed size.
Even if a force is applied it does not readily
change its shape, or volume.
The result is that the atoms vibrate about a fixed
Arrangement of Particles - 1
• Closely packed
• Strongly bonded to neighbours
• held rigidly in a fixed position
• the force of attraction between particles
gives them PE
are both known as fluids because they FLOW.
The thermal energy (due to an increase in temperature)
is greater allowing the atoms to move farther apart.
The binding forces are less and the atoms are able to
roll over each other. This gives rise to the macroscopic
properties of liquids.
Liquids do not maintain a fixed shape it takes the shape
of the container. Like a solid, it is not readily
compressible only a very large force can, significantly
change its volume.
Arrangement of Particles - 2
• Still closely packed
• Bonding is still quite strong
• Not held rigidly in a fixed position and
bonds can break and reform
• PE of the particles is higher than a solid
because the distance between the particles
The forces of attraction are so weak and the
thermal energy is so high (due to another
increase in temperature), the atoms do not
even stay close together.
They move very rapidly in a random manner
filling the container and, occasionally colliding
with one another.
The speed at which the atoms are moving is so
fast that when they do collide, the force of
attraction is not strong enough to, keep them
together and, they fly off in a new direction.
A gas has neither a fixed shape nor a fixed
volume it will expand to fill its container.
Arrangement of Particles - 3
• Widely spaced
• Only interact significantly on closest
approach or collision
• Have a much higher PE than liquids
because the particles are furthest apart
At extremely high temperatures such as those
found in stars, atoms are ionised. The result is a
collection of nuclei (ions) and electrons referred
to as plasma.
Changes of State
Add energy to ice and it turns to water. Add energy
to water and it turns to steam. The state of matter
depends upon its temperature and the pressure that
is exerted upon it.
To change state, a transfer of energy is required.
A substance can undergo changes of state or phase
changes at different temperatures.
Changes of State - 2
The moving particle theory can be used to
explain the microscopic behaviour of these
When the solid is heated the particles of the
solid vibrate at an increasing rate as the
temperature is increased the vibrational KE of
the particles increases.
Changes of State - 3
At the melting point, a temperature is reached at
which the particles vibrate with sufficient thermal
energy to break from their fixed positions and begin
to slip over each other.
As the solid continues to melt more and more
particles gain sufficient energy to overcome the
forces between the particles and over time all the
solid particles are changed to a liquid.
The PE of the system increases as the particles
Changes in State - 4
As the heating continues the temperature of the
liquid rises due to an increase in the vibrational,
rotational and translational energy of the particles.
At the boiling point a temperature is reached at
which the particles gain sufficient energy to
overcome the inter-particle forces and escape into
the gaseous state. The PE increases.
Continued heating at the boiling point provides the
energy for all the particles to change.
Solid - liquid
Liquid - gas
Temp / oC
Changes of State
Thermal energy given out
Thermal energy added
This is the process whereby a solid changes
directly into a vapour without passing through
the liquid phase.
Carbon dioxide will do this at atmospheric
The process of evaporation is a change from the
liquid state to the gaseous state which occurs at
a temperature below the boiling point.
The Moving Particle (Kinetic) theory can be
applied to understand the evaporation process.
Explanation - evaporation
A change of state from liquid to gas that takes
place at the surface of the liquid.
The temperature of any body is related to the
mean kinetic energy of its molecules. As the
molecules move in a random manner, some
molecules may collide. Some may lose kinetic
energy and some may collide and increase
kinetic energy, enough to overcome the
attractive forces of their neighbouring molecules.
As the higher kinetic energy molecules have
escaped, the mean kinetic energy of the liquid has
been reduced. This means the liquid left behind
has been cooled and there is a corresponding
This is the principle used by evaporative air
conditioners and perspiration.
Condensation is the opposite process to
evaporation. This is the cooling of a gas to a
liquid. When water vapour molecules collide with
a cold can of Coke, giving up sufficient kinetic
energy, they condense into a liquid.
Condensation is a warming process.
The kinetic energy lost by the gas molecules warms
the surface that they strike. A steam burn is more
dangerous than a boiling water burn at the same
temperature. Steam gives up energy when it
condenses to the liquid that wets the skin.
At a macroscopic level, temperature is the degree of
hotness or coldness of a body as measured by a
Temperature is a property that determines the direction
of thermal energy transfer between two bodies in
Are you a good thermometer?
Thermal equilibrium occurs when the
temperature of 2 bodies, that are in contact, are
Heat will flow from the warmer body to the colder
body until the two objects reach the same
They will then be in Thermal Equilibrium.This is
how a thermometer works
Nearly all matter expands when its temperature
increases and conversely contracts when
A thermometer uses the expansion and
contraction of a liquid in a glass capillary tube
with a scale to measure the expansion or
What other examples can you think of?
Thermometer - scales
A temperature scale is constructed by taking two
fixed, reproducible temperaturas.
The upper fixed point is the boiling point of
pure water at atmospheric pressure.
The lower fixed point is the melting point of
pure ice at atmospheric pressure.
Use the idea of thermal
equilibrium to explain
1. Why kitchen floors are generally cold to bare
feet during winter
2. Why hot water bottles are used in winter
3. Why carpet feels warmer than wood
4. Why do car windows fog in winter
Temperature - Microscopic
At a microscopic level, temperature is related to the
random motion of the atoms or molecules in a
substance. In an ideal gas temperature is a measure of
the average kinetic energy per molecule associated
with its movement in the substance.
Temperature is not a measure of the total kinetic
energy of the atoms or molecules in a substance.
There is twice as much kinetic energy in 2 litres of
boiling water than in 1 litre.
The temperature is however the same in both
containers as the mean kinetic energy of the
atoms or molecules is the same.
The Internal (thermal) energy of a body is
the total energy associated with the thermal
motions of the particles.
It can comprise of both kinetic and potential
energies associated with particle motion:
Kinetic energy arises from the translational
and rotational motions,
Potential energy arises from the forces
between the molecules.
What can change a system?
Heat and work can change the state of the
system but they are not a property of the system.
They are not characteristic of the state itself but
rather they are involved in the thermodynamic
process that can change the system from one
state to another.
Touch a hot saucepan an energy is transferred to your
hand as the saucepan is warmer than your hand. If
however you touch ice, energy is transferred from your
hand to the ice.
Thermal energy is always transferred from a hotter
substance to a cooler one.
Heat - 2
The term heat represents energy transfer due to
a temperature difference and occurs from higher
to lower temperature regions.
Most people tend to believe that all matter
All matter contains a number of forms of energy
but not heat.
Heat - 3
Heat is the transfer of energy from a body with higher
temperature to one of lower temperature.
Once the energy is transferred it ceases to be heat. It
becomes kinetic energy.
Heat will not necessarily flow from a body with
more total molecular kinetic energy to one with
less total molecular kinetic energy. A bowl of
warm water has much more total molecular
kinetic energy than a red hot bolt. If the red hot
bolt is immersed into the warm water heat will
flow according to temperature difference.
Temperature is measured in degrees Celsius
(oC) or Kelvin (K) (the absolute scale).
Where Temp in K = Temp in oC + 273(.15)
Temp in K is known as the absolute temperature
Heat Capacity/Thermal Capacity
When different substances undergo the same
temperature change they can store or release
different amounts of energy.
The temperature change that occurs when a
substance absorbs heat depends on the amount of
the substance. In order to quantify heat we must
specify the amount of the substance.
The calorie is defined as:
The amount of heat required to raise the
temperature of 1 g of water by 1oC.
A kilocalorie is the heat required to raise the
temperature of 1 kg of water by 1oC.
The S.I. unit of heat is the same as all other
forms of energy - the Joule (J). 1 calorie =
Heat Capacity - 2
Heat capacity = Q / T in JK-1
Q = the change in thermal energy in
T = the change in temperature in Kelvin
Defined as the amount of energy to change
the temperature of a body by unit
temperature and applies to a specific BODY.
Heat Capacity - 3
A body with a high heat capacity will take in
thermal energy at a slower rate than a
substance with a low heat capacity because
it needs more time to absorb a greater
quantity of thermal energy.
They also cool more slowly because they
give out thermal energy at a slower rate.
Specific Heat Capacity
Why is it that when fried in the
same way for the same time, you
can eat fried mushrooms but fried
tomatoes burns your tongue?
Why is it that a pizza can be just
right but the pineapple is always
The answer lies in the fact that different
substances have different capacities for storing
heat. Put a litre of water in a saucepan and heat,
it may take a few minutes to boil. Put a metal
knife on the same hotplate and it will reach the
same temperature much more quickly.
If we were given 1g of both iron and water, we
would have a different number of molecules of
different type and mass in each sample.
Specific Heat Capacity - 2
Water uses energy to increase the rotation of
molecules, internal vibration and bond stretching. Iron
atoms use the energy to increase the translational
This means it takes 8 times the amount of heat to raise
1g of water by 1 oC than it does for iron.
(The more water in the food the hotter it will seem)
Specific Heat Capacity - 3
Specific Heat Capacity - 4
Defined as the quantity of heat required to raise the
temperature of a unit mass of a substance by 1 degree
is known as the specific heat capacity.
Unit mass is normally 1kg, and unit temperature rise is
Specific Heat Capacity = Q / (mT)
in J kg -1 K-1 where m is the mass of the material
We use the symbol c for specific heat capacity so the
Q = mcT
For an object made of one specific material then
Heat Capacity = m x Specific Heat Capacity
Water has a specific heat of 4180 joules/kgoC. This
means it takes 4180 J of energy to raise the
temperature of 1kg of water by 1oC.
Specific Heat Capacity - 5
Unit masses of different substances contain
different numbers of molecules
of different types
of different masses
If the same amount of internal energy is added to
each unit mass it is distributed amongst the
Specific Heat capacity - 6
The average energy change of each molecule will be
different for each substance. Therefore, the temperature
changes will be different. So the specific heat capacities
will be different.
How much heat energy would be required to
raise the temperature of 5 kg of water from
19oC to 44oC?
• m = 5 kg
• c = 4200 J/kgoC
• Ti = 19oC
• Tf = 44oC
• Q = mcT
• Q = 5 x 4200 x (44 -19)
• Q = 5.25 x 105 J
If 40 000 J of heat are provided to 4 kg of
water at 20oC, what final temperature will be
• Q = 40 000 J
• m = 4 kg
• c = 4200 J/kgoC
• Ti = 20oC
• Q = mcT
• 4 x 104 = 4 x 4200 x (Tf - 20)
• Tf = (4 x 104/4 x 4200) + 20
• Tf = 22.4oC
Methods of finding the S.H.C
The specific heat capacity can be found in two
1. SHC of Liquids
Calculations - Liquids
Electrical Energy input is equal to the thermal
energy gained by the liquid and the calorimeter
– this is the assumption that we are making
Work done = V x I x t
Energy gained by liquid = ml cl Tl
Energy gained by calorimeter = mc cc Tc
Calculations - Liquids -2
Using conservation of energy
Electrical energy in = thermal energy gained by
liquid + thermal energy gained by calorimeter
V I t = ml cl Tl + mc cc Tc
The only unknown is the specific heat capacity of
2. SHC of Solids
Calculations - Solids
Again using the conservation of energy. Electrical
Energy input is equal to the thermal energy gained by
Electrical energy = V x I x t
Energy gained by solid = ms cs Ts
V x I x t = ms cs Ts
The only unknown is the specific heat capacity of the
How much water could be boiled using an
immersion heater that draws a 5A current in 15
minutes from room temperature (20oC)?
• VIt = mcT
• m = Vit/cT
• m = (240 x 5 x 15 x 60)/(4200 x (100 -20))
• m = 1.08 x 106/3.36 x 105
• m = 3.2 kg
A person wants to make 4, 250ml cups of hot
coffee. If they were to use an electric kettle 240
V that used 1500W, how long would it take to
boil the minimum amount of water from 25oC)?
• P = VI and VIt = mcT
• Pt = mcT
• t = mcT/P
• t = (4 x 0.25) x 4200 x (100 - 25)/1500
• t = (1 x 4200 x 75)/1500
• t = 315000/1500
• t = 210 s (or 3½ min)
3. Method of mixtures
In the case of solid, a known mass of solid is
heated to a known temperature (usually by
immersing in boiling water for a period of time).
Then it is transferred to a known mass of liquid
in a calorimeter of known mass.
The change in temperature is recorded and from
this the specific heat capacity of the solid can be
Energy lost by block = Energy gained by liquid and
mb cb Tb = mw cw Tw + mc cc Tc
the SHC of water and the calorimeter are needed.
Ten silver spoons, each with a mass of 30g, are
removed from a pan of boiling water, quickly
dried, and then placed in a pan of water at room
temperature (20oC). The pan contains 500g of
water. The temperature rises to 23oC.
What is the specific heat capacity of silver?
• (mcT)silver = (mcT)water
• (0.03 x 10) x cs x (100 - 23) = 0.5 x 4200 x (23 - 20)
• c x 0.3 x 77 = 2100 x 3
• 23.1c = 6300
• c = 6300/23.1
• c = 270J/kgoC
Determine the final temperature of a 0.2 kg mass
of hot coffee at 90oC contained in a foam-
insulating cup if 0.1 kg of cold water at 10oC is
poured into it? Assume the specific heat capacity
of coffee is 4000 J/kgoC.
What will be the final temperature reached when
a 250 g rod of copper (ccopper = 385 J/kgoC) is
taken from a beaker of boiling water and plunged
into 100g of water at 20oC contained in another
Evaporation takes place at the surface of a
liquid. A change of state from liquid to gas can
also take place within the liquid.
The gas that forms beneath the surface occurs
as bubbles which move up and out into the
surrounding air. This is also called boiling.
The pressure of the bubbles within the bubble
must be great enough to resist the pressure of
the liquid water.
Does evaporation always
happen at same speed?
Evaporation can be increased by
• Increasing temperature (more particles have a
• Increasing surface área (more particles closer to the
• Increasing air flow above the Surface (gives the
particles somewhere to go to)
The thermal energy which a particle absorbs in
melting, vaporising or sublimation or gives out in
freezing, condensing or sublimating is called
Latent Heat because it does not produce a
change in temperature.
During a change of state, there is no change in
temperature until all of the substance has
Latent Heat - 2
If we study boiling water and steam that are both at
100oC, they both have the same average kinetic energy.
The molecules in steam however, has much more
potential energy as they are free to move and are not
held together. When water turns to steam, no
temperature rise is observed as the energy absorbed
goes into increasing the potential energy.
Let us look at what happens when 1.0 kg of water is
heated from -20oC where it is ice, until it has become
steam at 100oC at 1 atm pressure (1.01 x 105Pa).
As heat is added, its temperature increases at the rate
of about 1oC for every 2.1 kJ of heat added to the ice.
When the temperature reaches 0 oC, the temperature
stops rising even though heat is still added. When 2100
J have been added, all the ice has turned to water and
temperature is still 0 oC.
Water - 2
The energy required to change 1 kg of a substance
from the solid to liquid state is called the latent heat of
fusion (Lf). This also refers to the amount of heat
released when a liquid is turned to solid. For water, the
Lf = 3.34 x 105 J.
The water will now increase in temperature at the rate
of 1 oC for every 4.2 kJ of heat added. When the
temperature reaches 100 oC, the temperature again
remains constant until all of the water is turned to
Water - 3
The energy required to change 1 kg of a substance
from the liquid to gaseous state is called the latent heat
of vaporisation (Lv). This also refers to the amount of
heat released when a gas is turned to liquid.
The heat required to change the state of a substance
can also be expressed mathematically.
Q = mL
The quantity of heat energy required to change
one kilogram of a substance from one phase to
another, without a change in temperature is
called the Specific Latent Heat of
Latent Heat = Q / m in J kg -1
Types of Latent Heat
The latent heat of fusion of a substance is less
than the latent heat of vaporisation or the latent
heat of sublimation.
When dealing with questions think about
• where the heat is being given out
• where the heat is being absorbed
• try not to miss out any part
How much heat is required to convert 40 g of ice
to water at 0oC?
Q = mL
Q = (4 x 10-2) x (3.34 x 105)
Q = 1.3 x 104 J absorbed
Water at 95oC is mixed with an equal mass of ice
at 0oC. Find the final temperature achieved.
Energy lost by water cooling = Energy gained by
ice melting + Energy gained by ice warming
mcT = mLf + mcT
m x 4200 x (95 - Tf) =
(m x (3.34 x 105)) + ((m x 4200 x (Tf - 0))
divide both sides by m.
399000 - 4200 Tf = 334000 + 4200 Tf
8400 Tf = 65000
Tf = 7.7 oC
A large polystyrene pot contains 2 kg of water at
20oC. Steam at 100oC is blown into the water
and the temperature reaches 50oC. Find the
mass of steam used.
• m2 = ?
• Ti = 100oC
• Tf = 50oC
• Lv = 2.26 x 106 J kg-1
• m1 = 2 kg
• c = 4200 J kg-1 oC-1
• Ti = 20oC
• Tf = 50oC
m1cT = m2Lv + m2cT
2 x 4200 x 30 =
m2 x (2.26 x 106) + m2 x 4200 x 50
m2 = (2 x 4200 x 30)/(2.26x106 + 4200 x 50)
m2 = 0.1 kg
Methods of finding Latent Heat
To find the latent heat of a substance similar
methods are used as for specific heat capacity.
The latent heat of fusion of ice can be found by
adding ice to water in a calorimeter.
Block of ice
Block of ice
The change in temperature is recorded and
from this the latent heat of fusion of the ice
can be found
Energy gained by block melting = Energy
lost by liquid and calorimeter
mb Lb = mw cw Tw + mc cc Tc
the SHC of water and the calorimeter are
Latent Heat of Vaporisation
Liquid in Calorimeter
The initial mass of the liquid is recorded
The change in temperature is recorded for heating
the liquid to boiling
The liquid is kept boiling
The new mass is recorded
Energy supplied by heater = energy to raise
temperature of liquid + energy use to vaporise
some of the liquid
(The calorimeter also needs to be taken in to
V I t = ml clTl+ me Le + mc ccTc
A 200W immersion heater is used to raise the
temperature of water to its boiling point. The
heater is left on for 4 minutes after the water
boils. What mass of water will be boiled off in
mLv = Pt
m x 2.26 x 106 = 200 x 240
m = 200 x 240/(2.26 x 106)
m = 2.12 x 10-2 kg
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