CHAPTER 11 Heat and matter.

• Distinguish between the motion of particles of gases and those of solids and liquids.
• Discuss the kinetic theory of gases and associated assumptions and be able to relate these assumptions to every day gaseous situations.
• Distinguish between Pressure and Force and be able to apply the pressure formula (P = F/A).
• dentify everyday application of pressure and discuss consequences of changing the area of contact.
• Recognise Boyle's Law and Charles' Law in either mathematical or graphical form and be able to apply them.
• Use the Combined Gas Equation and the Ideal Gas Equation to solve problems.
• Use the Ideal Gas Equation to find particular characteristics of gas particles - kinetic energy, average velocity etc. (PV = NkT; KE_av = 3/2 kT)
• Recognise that temperature changes cause all materials to expand and contract by different amounts.
• Understand and use the terms: linear expansion of solids, volume expansion of liquids, co-efficient of linear expansion, and coefficient of volume expansion.
• Solve problems involving linear and volume expansion and contraction.
• Discuss the volume changes that occur in water with decrease in temperature and the consequences of these changes.

SCIENTIFIC PROCESSES

• Plot and interpret graphs illustrating Boyle's Law and Charles' Law.
• Discuss the implications of Boyle's Law and Charles' Law to every day situations.
• Use appropriate units, tables, graphs, and communication to write reports on experiments that attempt to verify Boyle's and Charles' Laws.
• Identify and discuss the use of dynamics and kinematics in developing the Ideal Gas Equation.
• Identify applications and discuss the significance of linear and volume expansions in the everyday uses of materials.

COMPLEX REASONING PROCESSES

• Discuss and develop the Ideal Gas Equation from basic kinematics and dynamics theory.
• Solve novel gas problems where the gas has other forms of internal energies such as rotation and potential energies.
• Solve novel and complex problems on linear and volume expansion.
• Critically discuss the significance of the different rates of expansion in everyday applications or novel situations.
• Use experimental data and graphs to determine the coefficient of expansion of materials.

CHAPTER 11 SUMMARY

• The kinetic theory of gas assumptions:
  (a)The particles of a gas are in constant random motion. They move at high speeds in straight lines unless they collide with the walls of the container or other particles. These collisions are elastic.
  (b)The particles of a gas are separated by large distances compared with the diameter of the particles which are assumed to be negligible in size.
  (c)The forces of attraction between particles are negligible.
  (d)The temperature of a gas is a measure of the average kinetic energy of the particles of the gas.
• Pressure is the force per unit area (P = F/A), and the unit is the Pascal (Pa).
• The quantities that are significant in understanding the behaviour of gases are volume(V), pressure(P), temperature(T) and the number of particles in the gas(N).
• Boyle's Law states for a fixed mass of gas at constant temperature, the pressure of a gas varies inversely to the volume. It is expressed mathematically as P₁.V₁ = P₂.V₂.
• Charles' Law states if the pressure and the number of particles of a gas remain constant, the volume of the gas increases proportionally with increase in temperature. Mathematically it is expressed as V₁/T₁ = V₂/T₂
• The combined gas equation combines both Boyle's and Charles' Laws into one equation: P₁.V₁/T₁ = P₂.V₂/T₂
• The Ideal Gas Equation takes account of the number of particles in the gas and is expressed as either: PV = NkT or PV = nRT. Where N is the number of molecules, k is Boltzmann's constant, n is the number of moles, and R is the universal gas constant.
• One mole of a gas is equal to 6.02 x 10²³ particles of a gas. This number is known as Avogadro's number.
• The average kinetic energy of the particles of a gas is equal to 3/2. k.T.
• All solids expand and contract with changes in temperature. The rate at which they expand is called the coefficient of linear expansion (a) and is the amount one metre of a solid expands with a temperature change of 1^oC.
• The change in length of a solid due to change in temperature is given by the formula:
  Dl = l_i.a.DT
• Expansion of solids can be an advantage or an disadvantage to society.
• The volume of a liquid also changes with change in temperature. The rate at which it expands with temperature is given by the coefficient of volume expansion (b), and is the amount one cubic metre of a liquid volume changes with a temperature change of 1^oC.
• The change in volume of a liquid due to change in temperature is given by the equation:
  DV = V_i.b.DT
• The expansion of water with temperature differs from other liquids. Between 4^oC and 0^oC, water expands as the temperature is decreased, giving water a maximum density and a minimum volume at 4^oC.

Return to Objectives-Summary Menu Page page.