STATES OF MATTER Based upon particle arrangement Based upon energy of particles Based upon distance between particles

Kinetic Theory of Matter Matter is made up of particles which are in continual random motion.

STATES OF MATTER SOLIDS Particles of solids are tightly packed, vibrating about a fixed position. Solids have a definite shape and a definite volume. Heat

STATES OF MATTER LIQUID Particles of liquids are tightly packed, but are far enough apart to slide over one another. Liquids have an indefinite shape and a definite volume. Heat

STATES OF MATTER GAS Particles of gases are very far apart and move freely. Gases have an indefinite shape and an indefinite volume. Heat

Liquid State Characteristic Properties The liquid state of matter has intermediate properties. Less orderly than solid state but more orderly than the gaseous state.

Liquid State Liquid state is explained on the basis of kinetic theory model as follows: Liquids are made up of molecules. Molecules in a liquid are quite close to each other. Force of attraction between the molecules in a liquid is quite large. The molecules in a liquid are in a state of constant random motion. The average kinetic energy of the molecules in a liquid is to their absolute temperature.

Properties of Liquid Diffusion There is diffusion in liquids but it is slower than in gases. Diffusion involves movement of molecules from higher concentration to lower concentration. Compressibility Liquids are relatively less compressible than gases.

Properties of Liquid Evaporation The process of conversion of a liquid into its vapours at room temperature is known as evaporation. Evaporation can be easily explained on the basis of kinetic theory. At a given temperature, the average kinetic energy of the liquid molecules is constant but all the molecules do not have the same kinetic energy.

Properties of Liquid Consequently, a certain fraction of molecules will have kinetic energies large enough to overcome the attractive forces of their neighbours and to escape into space above the liquid surface. Evaporation causes cooling. Rate of evaporation is influenced by the surface area of the liquid, the temperature and the strength of intermolecular forces of attraction.

Vapor Pressure The Macroscopic View The vapor pressure of a liquid is the equilibrium pressure of a vapor above its liquid (or solid); that is, the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container. Examples: substance vapor pressure at 25oC diethyl ether 0.7 atm bromine 0.3 atm ethyl alcohol 0.08 atm water 0.03 atm

The vapor pressure of a liquid varies with its temperature, as the following graph shows for water. The line on the graph shows the boiling temperature for water. As the temperature of a liquid or solid increases its vapor pressure also increases. Conversely, vapor pressure decreases as the temperature decreases. The vapor pressure of a liquid can be measured in a variety of ways. A simple measurement involves injecting a little of the liquid into a closed flask connected to a manometer. 

The Microscopic View When a solid or a liquid evaporates to a gas in a closed container, the molecules cannot escape. Some of the gas molecules will eventually strike the condensed phase and condense back into it. When the rate of condensation of the gas becomes equal to the rate of evaporation of the liquid or solid, the amount of gas, liquid and/or solid no longer changes. The gas in the container is in equilibrium with the liquid or solid. Microscopic equilibrium between gas and liquid. Note that the rate of evaporation of the liquid is equal to the rate of condensation of the gas. Microscopic equilibrium between gas and solid. Note that the rate of evaporation of the solid is equal to the rate of condensation of the gas. The pressure exerted by the gas in equilibrium with a solid or liquid in a closed container at a given temperature is called the vapor pressure.

Factors That Affect Vapor Pressure Surface Area: the surface area of the solid or liquid in contact with the gas has no effect on the vapor pressure. Types of Molecules: the types of molecules that make up a solid or liquid determine its vapor pressure. If the intermolecular forces between molecules are: relatively strong, the vapor pressure will be relatively low. relatively weak, the vapor pressure will be relatively high.

Temperature: at a higher temperature, more molecules have enough energy to escape from the liquid or solid. At a lower temperature, fewer molecules have sufficient energy to escape from the liquid or solid. Microscopic equilibrium between gas and liquid at low temperature. Note the small number of particles in the gas. Microscopic equilibrium between gas and liquid at high temperature. Note the large number of particles in the gas.

Heat of Vaporization The Heat (or Enthalpy) of Vaporization is the quantity of heat that must be absorbed if a certain quantity of liquid is vaporized at a constant temperature. In a solution with both a vaporized and liquidized states, the kinetic energy of the vapor is higher than the kinetic energy of the liquid. Temperature follows kinetic energy, showing a lower temperature in the remaining liquid. The Enthalpy of Vaporization is measured using constant temperature, meaning that something must be added to bring the lower temperature to the temperature of the solution prior to vaporization. To raise the temperature (and as a result, the kinetic energy), heat is added. The Enthalpy of Vaporization measures the amount of heat added, because it is the quantity that must be absorbed for a liquid to remain at constant temperature during vaporization. ΔHvap is expressed in kJ/mol. ΔHvap is the change in enthalpy of vaporization Hvapor is the absolute enthalpy of the gas state of a compound or element Hliquid is the absolute enthalpy of the liquid state of a compound or element

Enthalpies is a state function under a specific set of conditions, but cannot be measured directly, but the given difference has a unique value that can be measured. Because heat is added to the system to maintain the temperature, vaporization is an endothermic process, hence ΔHvaporization is always positive.

Molar Heat of Vaporization Here is the definition of the molar heat of vaporization: the amount of heat necessary to boil (or condense) 1.00 mole of a substance at its boiling point Note the two important factors: It's 1.00 mole of a substance there is no temperature change Keep in mind the fact that this is a very specific value. It is only for one mole of substance boiling. The molar heat of vaporization is an important part of energy calculations since it tells you how much energy is needed to boil each mole of substance on hand. (Or, if we were cooling off a substance, how much energy per mole to remove from a substance as it condenses.)

q = ΔHvap (mass/molar mass) Every substance has its own molar heat of vaporization. The units are usually kilojoules per mole (kJ/mol). Sometimes the unit J/g is used. The first unit is technically the more correct unit to use. The molar heat of vaporization for water is 40.7 kJ/mol. Remember the value!!! Molar heat values can be looked up in reference books. They are determined by experiment. The molar heat of vaporization equation looks like this: q = ΔHvap (mass/molar mass) The meanings are as follows: q is the total amount of heat involved ΔHvap is the symbol for the molar heat of vaporization. This value is a constant for a given substance. (mass/molar mass) is the division to get the number of moles of substance

Trouton's rule ∆Hvap/Tb ≈ 88 J mol-1 K-1 = ∆Svap Trouton's rule states that the entropy of vaporization is almost the same value, about 85–88 J K−1 mol−1, for various kinds of liquids at their boiling points. The entropy of vaporization is defined as the ratio between the enthalpy of vaporization and the boiling temperature. ∆Hvap/Tb ≈ 88 J mol-1 K-1 = ∆Svap