Molecular model

2.1.1 States of matter

2.1.3 Evaporation

Molecular model

  1. Molecular structure

    State Arrangement of molecules Force of attraction between molecules
    Solid Held in a rigid lattice Very strong
    Liquid Held together loosely, but are free to move past each other Weaker: this allows liquids to flow
    Gas Free to move, travelling rapidly in a straight line until colliding None: the large distances between the molecules allow the gas to change volume

  2. Kinetic energy

    1. The absolute temperature of a gas is directly proportional to the mean kinetic energy of its molecules
    2. The pressure of a gas is directly proportional to the mean kinetic energy of its molecules
    3. The temperature of a gas is directly proportional to the pressure, at a constant temperature

  3. Brownian motion

    1. The random motion of molecules in a suspension is evidence for the kinetic molecular model of matter
    2. This is caused by the suspended molecules being constantly bombarded by the molecules in the fluid
    3. Massive molecules can be moved by the constant bombardment from light, fast-moving particles