Kinetic Molecular Theory Video

The constant motion of particles mean they have kinetic energy. Chapter 10 The Kinetic-Molecular Theory is based on the idea that particles of matter are always in motion. The constant motion of particles mean they have kinetic energy. Their kinetic energy can be used to explain the different states of matter, (solid, liquid, and gas) and their properties.

States of Matter Describe the intermolecular forces and the amount of kinetic energy for each.

Kinetic Molecular Theory of Liquids 3. Liquids have the ability to diffuse, but it occurs slower than gases, because their particles are closer together. 1. At normal atmospheric pressure, most substances are more dense in a liquid state than in a gaseous state. 2. Liquids are less compressible than gases

Kinetic Molecular Theory of Liquids Vaporization- the process by which a liquid or solid changes to a gas. Evaporation is the process by which particles escape from from a non-boiling liquid and enter the gas phase. When a substance cools, its KE decreases and its particles condense until the substance becomes a solid. The physical change of a liquid to a solid as heat energy is removed is called freezing or solidification.

Kinetic Molecular Theory of Solids 1. Definite shape and volume. 2. Definite melting point. The temp at which a solid becomes a liquid 3. In general, substances are most dense in the solid state 4. Incompressible 5. Low rate of diffusion

Kinetic Molecular Theory of Gases 3. Gas particles are in continuous, rapid, random motion 4. There are no forces of attraction between gas particles (when they collide, they immediately bounce off of each other). 5. The temperature of a gas depends on the average kinetic energy of the particles of the gas. (Higher temperatures results in increased KE) (lighter gases like Hydrogen have less KE than heavier gas molecules, like Oxygen at the same temperature). 1. Gases consist of a large number of tiny particles that are far apart. 2. The pressure exerted by gases is caused by elastic collisions of the gas molecules with the walls of the container. (elastic collisions are collisions where there is no net loss of KE, KE is transferred from and gas particle to the other one)

Ideal Gases vs. Real Gases A hypothetical gas that perfectly fits all the assumptions of the Kinetic Molecular Theory of Gases A gas that does not behave completely according to the assumptions of the kinetic molecular theory of gases. Most real gases will behave like ideal gases at high temperatures and low pressures

Changes in States of Matter

Changes of State and Equilibrium Explain why alcohol has an odor that is easily detected. Some of the gas molecules in an opened bottle of alcohol have enough energy to leave the liquid phase and evaporate. In a closed bottle of alcohol, the molecules constantly go back and forth between the gas phase and the liquid phase. Eventually, the rate of condensation equals the rate of evaporation, and a state of equilibrium is established. Equilibrium is a condition in which two opposing changes occur at equal rates.

Energy and Boiling Energy (heat) must be added continuously in order to keep a liquid boiling. When a liquid begins to boil, the temperature remains constant, despite the addition of energy (heat) The added energy at a liquid’s boiling point is used the overcome the intermolecular forces in liquid as it phase changes to its gas phase.

Molar Heat of Vaporization The molar heat of vaporization is the amount of energy as heat that is needed to vaporize one mole of liquid at its boiling point. Every substance has its own molar heat of vaporization Q =m ΔH vap

Molar Heat of Fusion This is a very specific value. It is only for one mole of substance melting. The molar heat of fusion is an important part of energy calculations since it tells you how much energy (heat) is needed to melt each mole of a solid at its melting point Q = m ΔH fus

CLASSWORK Molar Enthalpy Worksheet