5.8 CHAPTER 5. THERMAL PROPERTIES AND IDEAL GASES
ideal gas
real gas
Pressure
Temperature
Figure 5.7: Gases deviate from ideal gas behaviour at low temperatures
Chapter 5 — Summary
See the summary presentation ( Presentation: VPisz at http://www.everythingscience.co.za)
- The kinetic theory of matter helps to explain the behaviour of gases under different conditions.
- An ideal gas is one that obeys all theassumptions of the kinetic theory.
- A real gas behaves like an ideal gas, except at high pressures and low temperatures. Under these
conditions, the forces between molecules become significant and the gaswill liquefy.
- Boyle’s law states that the pressureof a fixed quantity of gas is inversely proportional to its
volume, as long as the temperature stays the same. In other words, pV =k or
p 1 V 1 = p 2 V 2.
- Charles’s law states that the volume of an enclosed sample ofgas is directly proportional to its
temperature, as long asthe pressure stays the same. In other words,
V 1
T 1
=
V 2
T 2
- The temperature of a fixed mass of gas is directly proportional to its pressure, if the volume is
constant. In other words,
p 1
T 1
=
p 2
T 2
- In the above equations, temperature must bewritten in Kelvin. Temperature in degrees Cel-
sius (temperature = t) can be converted to temperature in Kelvin (temperature = T) using the
following equation:
T = t + 273
- Combining Boyle’s lawand the relationship between the temperatureand pressure of a gas,
gives the general gas equation, which applies as longas the amount of gas remains constant.
The general gas equation is pV = kT, or
p 1 V 1
T 1
=
p 2 V 2
T 2
