• Imagine molecules of gas that are free to move around in a box
• The molecules in the gas move around randomly at high speeds, colliding with surfaces and exerting pressure upon them
• The?temperature?of a gas is related to the?average speed?of the molecules:
  • The?hotter?the gas, the?faster?the molecules move and vice versa
  • Hence, the molecules collide with the surface of the walls?more frequently

   

Gas molecules move about randomly at high speeds

• This is because their?kinetic energy?increases

• Heating a system will change the energy stored in a system by?increasing the kinetic energy?of its particles
  • The Kelvin?temperature?of the gas is related to the average?kinetic energy?of the molecules

   

• This increase in kinetic energy (and therefore energy stored in the system) can:
  • Cause the?temperature?of the system to increase
  • Or, produce a?change of state?(solid to liquid or liquid to gas)

   

• The internal energy of a gas is the sum of the kinetic energy of all the molecules
• The higher the temperature, the higher the average kinetic energy of the molecules and vice versa
  • This means they move around?faster

   

As the container is heated up, the gas molecules move faster with higher kinetic energy. The energy stored within the system - the internal energy - therefore increases

• If the temperature of a gas is increased, the particles move faster and gain?kinetic energy
  • Therefore, they will collide more with each other and the container leading to an increase in pressure

   

• The temperature (in Kelvin) is?proportional?to the average kinetic energy of the molecules

T ∝ KE

ANSWER:? B

• • When evaporation takes place, the more energetic molecules are leaving the surface of the liquid
  • Since the more energetic molecules have left, the?average kinetic energy per molecule?must?decrease
    • Therefore,?A, C?&?D?are not correct

     

  • Temperature is?proportional?to the average kinetic energy per molecule, therefore the?temperature?also?decreases

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