Heat and states of matter

Kinetic theory of matter

  • all matter is in constant random motion

  • The distance between molecules deturmines the state of matter

  • The strength of intermolecular forces deturmines the distance between molecules

    • The stronger the attraction between molecules, the closer the molecules will be to each other

Gases

  1. Very weak intermolecular forces

  2. Large distances between molecules

  3. Very low density

  4. Not definite volume

    1. molecules will separate as far apart as possible

  5. Translational motion

    1. Move from place to place

    2. Flow - molecules move past each other

  6. compressable

Liquids

  1. Medium/strong intermolecular forces

  2. Molecules close together

  3. High density

  4. Molecules remain in contact but are able to move past each other

  5. Rotational motion

    1. Molecules move past each other

  6. no definite shape

  7. Definite volume

  8. Incompressible

Solids

  1. Strong intermolecular forces

  2. Molecules close together

  3. High density

  4. Molecules remain in fixed relative positions

  5. Vibrational motion

    1. Molecules can’t move past each other

  6. definite shape

  7. Definite volume

  8. Incompressible

Crystalline solids / regular solids - consist of repeating three dimensional arangment of atoms (have a definite melting point)

Amorphous solids = lack an orderly internal structure and usually melt over a range of tempatures

Changes in state of matter

  1. Solid —> Gas = Sublimation

  2. Solid —> Liquid = Melting / Fusion

  3. Liquid —> Gas = Vaporization

  4. Liquid —> Solid = Freezing

  5. Gas —> Liquid = Condensation

  6. Gas —> Solid = Deposition

Endothermic energy and phase changes - a process in which energy is absorbed from the environment

Exothermic energy and phase changes - a process in which energy is released to the environment

Law of conservation of energy - energy released by the surroundings is equal to the energy absorbed by the system

Calculating heat changes

Q = m c T

Q = heat (joules)

M = mass (grams)

C = specific heat (J/G*C)

T = change in Tempature (C or K)