Solids and Liquids
Properties of solids:
• Definite shape • Definite volume
• Solid particles (atoms/molecules) move very slowly
• Very densely packed
Solids and Liquids
Properties of liquids: • No definite shape
• Definite volume
• Particles (atoms/molecules) move faster than solids, not as densely packed as solids • Liquids flow
• Weak attractive forces
Properties of Gases
Gases have many properties that make them unique and very different from
liquids or solids
•Gases have very low density – their particles have a great deal of distance
between them
•Like liquids, gases are considered to be fluids because they can flow. Gas particles are far apart so they can move
Properties continued…..
•Gases have no definite volume – this means they can expand or be compressed
•Gases will fill their container – gas particles
are in constant, random motion and collide with each other and spread out to fill any
container they are in.
•The collisions involving gas particles are
Properties continued……
•The temperature of a gas is directly related to the kinetic
energy of the gas – the warmer the gas the more
Properties of Gases
• Unlike solids or liquids, gases have no
definite shape or volume. Gas particles are moving very fast, with no attractive forces between them.
• There is also a great deal of space
between them so they can be
compressed or they can expand.
• All these properties allows gases to do
Diffusion and Effusion
The mixing of gaseous particles caused by their
random motion is called
diffusion.
Gases will spread out spontaneously and mix with other gases without
Effusion
Effusion is the reason balloons
filled with helium will go flat after
Pressure
Before we can examine the
behavior of gases in greater
detail we first must take a look
at pressure.
Pressure is defined as the
amount of force per unit
Gases exert
pressure by
colliding with
the walls of
their
Gas particles also
exert pressure on
Barometers are
used to measure
the air pressure
of the
Units of pressure
There are numerous units used to
measure pressure. The most common in science are:
•Atmospheres (atm)
•Torr (torr)
•Pascals (Pa)
Unit conversions
1 atm = 760 torr = 101.3 kPa
Example #1
Convert 500 torr to atm
More conversions
Convert 400 kPa to torr400 kPa x 760 torr__ = 3000 torr 101.3 kPa
Convert 0.75 atm to kPa
Standard temperature
and pressure (STP)
Standard temperature and
pressure (STP) are
Boyles’ Law
• Pressure and
volume of gases are inversely related. If the pressure on a volume of gas
increases, the
volume decreases.
• If the pressure
decreases, the
Calculations involving Boyle’s
Law
P
1V
1= P
2V
2The initial pressure times the initial volume is equal to the change in pressure times the
Example 1
A volume of gas is at a pressure of 1.5 atm and a volume of 3 liters. If the pressure on the gas changes to 4 atm,
what is the new volume of the gas?
Example 2
A volume of gas is at a pressure of 800 torr and a volume of 2.5 liters. If the volume of the gas changes to 4 liters, what is the new
pressure on the gas?
Example 3
A volume of gas is at a pressure of 1.2 atm and a volume of 125 liters. If the pressure on
the gas changes to 800 torr, what is the new volume of the gas?
1.2 atm x 125 L = 1.05 atm x V2 V2 = 142 L
Charles’ Law
• Volume and temperature of a gas are directly related. If the temperature of a gas increases, the volume also increases.
How temperature of a gas
changes its volume
As a gas is heated the particles move faster and spread out more to increase
the volume. The opposite
Calculations involving
Charles’ Law
V1 = V2 T1 T2
The temperature must be in Kelvin!!! Pressure remains a constant in
Example #1
If 25 L of gas are at a temperature of
275 K and the temperature increases to 300 K, what is the new volume of the gas?
25 L = V2 275 K 300K
Example 2
If 5.6 L of gas are at a temperature of
30 °C and the temperature decreases to 3 °C what is the new volume of the gas?
5.6 L = V2 303 K 276K
V2 =5.1 L
This law is similar to Charles’
Law in its relationships
As the temperature of a gas increases, the pressure of that also increases.
The increased temperature gives the gas more energy which makes the particles move faster and increases the collisions against the
It is because of
this relationship
that you should
keep all aerosol
cans away from
Guy-Lussac’s Law
P1 = P2 T1 T2
The temperature must be in Kelvin!!! Volume remains a constant in
Example 1
Find the pressure of a volume of gas if the initial pressure is 100 kPa at temperature of
300 K if the temperature goes up to 400 K.
100 kPa = _P2__ 300 K 400 K
Example 2
Find the temperature of a volume of gas if the initial temperature is 50 °C and a
pressure of 760 torr changes to a pressure of 2 atm.
1 atm = 2 atm 323 K T2
