Mod 2

• Charles' Law

  An experimental gas law that explains how gases tend to expand when exposed to high temperature
• Charles' Law


  The volume of an ideal gas is directly proportional to the absolute temperature at constant pressure

  
• When the pressure of a gas is held constant, and there is an increase in its temperature, its volume also increases

  
• Situations where Charles' Law is at play

  • A flat basketball on a bright sunny day expands as the temperature increases
  • An over-inflated pool float on a hot day can swell under the sun and eventually bursts
• Kinetic Molecular Theory (KMT)

  When the temperature is increased, the kinetic energy (KE) of the gas is also increased. To keep the pressure constant, the volume of the container must increase.

  
• If the temperature of a gas is reduced, the volume of the container must be reduced also in order to maintain the same pressure

  
• The density of a gas decreases with the increase in temperature
• Hot air balloons are used by scientists for meteorological purposes due to Charles' Law
• Charles' Law


  A special case of the ideal gas laws where the volume of a fixed mass of a gas is directly proportional to the temperature

  
• Solving problems involving Charles' Law

  1. Convert temperature from degrees Celsius to Kelvin, then add 273

  2. All temperatures used in gas law calculations must be in Kelvin (K)

  
• Charles' Law equation


  V1/T1 = V2/T2
• The standard temperature is 0°C or 273 K
• An increase in temperature of a gas will cause an increase in its volume, while a decrease in volume of a gas will cause an increase in its temperature, as the pressure is held constant

  
• The kinetic energy of the molecules of gas is affected when the air inside a hot air balloon is exposed to heat
• Heat energy, also known as thermal energy, occurs when the hot air rises which causes the hot air balloon to float
• Charles' Law provides an explanation of how hot-air balloons work
• Activity 1: Investigating the relationship between volume and temperature at constant pressure of a gas in a mathematical way


  Use Charles' Law equation: V1/T1 = V2/T2

  
• Sample problems using Charles' Law

  • A sample of Freon gas at 760 mmHg has a volume of 12.0 L and a temperature of 44°C. Find the new volume of the gas after the temperature has been increased to 85°C at 760 torr.
  • A gas occupies 221 cm3 at a temperature of 0°C and pressure of 760 mm Hg. What will its volume be at 100°C?

  
• The hot-air balloon works because of Charles' Law
• At constant pressure, when the volume changes, the volume-temperature relationship shows a straight line on the graph which indicates a direct proportion to each other

  
• The facts, information and explanation are clearly, concisely and logically discussed