Credit: Diya Mundade
States of Matter
Solids, Liquids, Gases
Movement of Particles
Solids vibrate in place
Liquid slide over each other
 Brownian Movement in chemistry is the random zig-zag motion of a
particle that is usually observed under high power ultra-microscope.
This movement resembles the exact motion of pollen grains in water as
explained by Robert Brown, hence, the name Brownian movement.
Properties of 3 States of Matter
Property
Closeness of
Particles
Solid
Liquid
Gas
Very close,
Close, but not as
Far apart,
particles are
close as solids
particles occupy
tightly packed
all available
space
Arrangement of
Homogenous
Randomly
Randomly
arranged
arranged
Vibrate in a
Slide over each
Move in all
fixed position
other
directions
Low energy
Greater energy
Highest energy
Fixed
Shape of
Shape of
container
container
Fixed
Volume of
Particles
Movement of
Particles
Energy of
Particles
Shape
Volume
Fixed
container
Intermolecular
High
Intermediate
Low
Force
Credit: Diya Mundade
Credit: Diya Mundade
Intermolecular
Low
Intermediate
High
Can flow
No
Yes
Yes
Can be
No
Difficult to do so
Yes
Space
compressed
Image
Gas Pressure
Gas pressure is caused when gas particles hit the walls of their container.
The more often the particles hit the walls, and the faster they are moving
when they do this, the higher the pressure.
Factors Affecting Gas Pressure
Volume of Container
As the volume increases, collisions between particles reduce,
hence gas pressure reduces. If the volume decreases, collisions
between particles increase, hence gas pressure increases.
Temperature
If particles have more (heat) energy they move faster and increase
the likelihood of collision, which increases gas pressure. Particles
with less energy move slower and reduce the likelihood of
collision, which reduces gas pressure.
Amount of Gas
If there is more gas, the number of collisions increase, hence
increasing gas pressure. If there is less gas, the number of
collisions decrease, hence decreasing gas pressure.
Credit: Diya Mundade
Credit: Diya Mundade
Interchange of State
Explaining Change of State According to Kinetic
Theory
As the substance is cooled, it loses energy. This reduces motion in the
particles, and causes intermolecular force to increase and intermolecular
space to decrease. Eventually the particles lose so much energy that they:
a) no longer move about freely, but must slide over each other, entering the
liquid state
b) no longer slide over each other, but must vibrate in place, entering the
solid state.
As the substance is heated, it gains energy. This increases motion in the
particles, and causes intermolecular force to reduce and intermolecular space
to increase. Eventually the particles gain so much energy that they:
a) no longer vibrate in place but can slide over each other, entering the
liquid state
b) no longer slide over each other, but can move about freely, entering the
gaseous state.
Evaporation:
Evaporation is the process in which a substance changes from it’s liquid to
it’s gaseous state over a range of temperatures. It is a surface phenomenon.
Greater temperature, surface area, and wind increase the rate of evaporation ;
and vice-versa.
In evaporation the particles closest to the surface have the most energy. They
only need to gain a small amount of energy to escape from the pull of the
attractive force that holds the particles together and enter the gaseous state.
Credit: Diya Mundade
Credit: Diya Mundade
Boiling:
Boiling is the process in which a substance changes from it’s liquid to it’s
gaseous state at a fixed temperature. It is a bulk phenomenon.
In boiling, the heat source is typically at the bottom of the container, and the
particles closest to the heat source gain the most energy upon heating. This
heat energy increases motion in the particles, and causes intermolecular force
to reduce and intermolecular space to reduce. Eventually the particles gain so
much energy that they no longer slide over each other, but can move about
freely, entering the gaseous state. However, since the particles are at the
bottom, they form bubbles within the liquid. These bubbles rise to the top,
and the gases escape the attractive force when the bubble bursts.
Others:

Sublimation is the process in which a substance changes from it’s solid to
gaseous state, without passing through the liquid state.

Deposition or de-sublimation is the process in which a substance changes
from it’s gaseous to solid state, without passing through the liquid state.

Freezing is the process in which a substance changes from it’s liquid state to
solid state.

Condensation is the process in which a substance changes from it’s gaseous
state to liquid state.

Melting is the process in which a substance changes from it’s solid to liquid
state.
Interpreting Heating and Cooling Curves
Changes of state can be investigated by measuring the temperature as a
substance changes state. There are two possibilities:

heat a substance and measure its temperature, for example, melt ice or
boil water

allow a substance to cool and measure its temperature
The diagram shows a cooling curve for salol. Notice that the temperature stays
the same during the state change (freezing), and this is the melting point (or
freezing point) of the salol.
Credit: Diya Mundade
Credit: Diya Mundade
The temperature stays the same during a state change because:

During melting and evaporating, internal energy increases as the
motion of particles increases and bonds are broken

During condensing and freezing, internal energy decreases as the
motion of particles decreases and new bonds are formed
Credit: Diya Mundade
Credit: Diya Mundade
Diffusion
Diffusion is the movement of a substance from a region of high concentration to a
region of low concentration.
E.g.: Coffee and water
1. Highly concentrated coffee
2. Coffee molecules begin to spread
3. Coffee molecules are now in a
molecules enter a cup of hot
out in between the water
lower concentration than they
water.
molecules.
started in.
Diffusion According to Particle Theory
In fluids, particles move randomly from place to place. The particles collide
with each other or with their container. This makes them change direction.
Eventually, the particles are spread through the whole container, without
any external interference.
Factors Affecting the Rate of Diffusion
…
Concentration Gradient / Concentration of
Particles:
The concentration difference is the difference between the amount of
diffusing particles present in the high-concentration area and lowconcentration area.
The rate of diffusion increases if the concentration gradient is low,
because there is greater space for the particles to move around; and
reduces if the concentration gradient is high, because there is less space.
Credit: Diya Mundade
Credit: Diya Mundade
Temperature:
Particles move due to the kinetic energy. As temperature increases, the
kinetic energy of each particle also increases which results in faster
particle movement. This increased speed allows them to diffuse faster.
Conversely, when the kinetic energy decreases so does molecular
movement. As a result, the rate of diffusion will reduce.
Mass of Diffusing Particles:
Heavier particles will move more slowly and so will have a slower rate
of diffusion. Smaller particles on the other hand will diffuse faster
because they can move faster.
Solvent’s Properties:
Viscosity and density greatly affect diffusion. If the medium that a
given particle has to diffuse through is very dense or viscous, then the
particle will have a harder time diffusing through it. So the rate of
diffusion will be lower. If the medium is less dense or less viscous, then
the particles will be able to move more quickly and will diffuse faster.
Credit: Diya Mundade