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Chemistry CHE 100 Notes
M. The Liquid State

  1. Attraction of Molecules (& Ions)

  2. Characteristics

    1. Limited expansion with constant temperature

    2. Shape take on shape or a container

    3. Volume: maintain their volumes

    4. Compressibility: slightly

    5. High Density: Compared to gases

    6. Mixability: Miscible vs Immiscible

  3. Evaporation

    1. Escape of molecules from the surface of the liquid

    2. The liquid's temperature is proportional to the average Kinetic Energy of the molecules

    3. Some molecules are moving faster and some moving slower than the average. Therefore some have higher Kinetic Energy and some have lower Kinetic Energy than the average

    4. The molecules with higher Kinetic Energy can escape leaving behind the lower energy molecules, therefore the average K.E. of liquid molecules is lowered (if heat does not enter from elsewhere)

  4. Condensation: Reverse of Evaporation

  5. Vapor Pressure

    1. Rate of evaporation = rate of condensation, therefore a dynamic equlibrium is reached, therefore the liquids vapor exerts a definite pressure called a vapor pressure. The pressure in the gas over the liquid is = 1ATM = PAir + P H2O

    2. What would happen if the temperature of the liquid was increased? The vapor pressure would increase

    3. What would happen if the atmosphere pressure above the liquid was equal to the vapor pressure? The boiling point is reached

    4. Boiling point

      1. For water: 100oC at one standard atmosphere

      2. When the vapor pressure of the liquid equals the surrounding atmospheric pressure

    5. Boiling point:

      1. If vapor pressure of the liquid = atmospheric pressure, the B.P. will be reached

      2. When at higher altitudes, what happens to B.P. of water?

  6. Heat of Vaporization or Heat of Condensation

    1. Heat of Vaporization

      1. Specific Heat of Vaporization of H2O is 540 cal/g or 2.26 x 106 j/kg at 100oC at 1 STD ATM

      2. Molar Heat of Vaporization of H2O is 9.72 kilocal/mole or 40.7 kiloj/mole at 100oC at 1 STD ATM

    2. Heat of Condensation = Heat of Evaporation

  7. Distillation

    1. Distillate

    2. Residue

  8. Surface Tension

    1. Property of a liquid that tends to draw the surface molecules into the body of the liquid, therefore reducing the surface to a minumun. The molecule at the surface of a liquid is attracted by other molecules beneath it, not above it.

  9. Mixability

    1. Miscible

    2. Immiscible

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