Internal Energy

  • the sum of kinetic and potential energy stored in molecules

  • for air:

    • potential energy of a parcel is related to how many molecules are in it

    • kinetic energy is related to the velocity of molecular motion (also determines the temperature)

   Examples:

which has larger internal energy:

Parcel A: mass = 5 grams, T = 30°C

Parcel B: mass = 5 grams, T = 10°C

ANSWER

Parcel A: mass = 100 grams, T = 0°C

Parcel B: mass = 1000 grams, T = 0°C

ANSWER

A lake at 15°C or a cup of coffee at 100°C

ANSWER