Liquids and Solids The Condensed States of Matter Chapter 10.2 – 10.3

A Model for Liquids Liquid molecules are free to slide past each other, so liquids, like gases, can flow.

Vaporization is… the conversion of a liquid to a gas or vapor. If the conversion occurs at the surface of a liquid that is not boiling, the process is called evaporation. Evaporation is a cooling process. The particle with the highest kinetic energy tend to escape first, leaving cooler particles behind.

Vapor Pressure is… pressure that results from the vapor particles colliding with the walls of the container. It is a force due to a gas above the surface of a liquid. (Vapor is the gaseous state of a substance that is a liquid or solid at room temperature).

Phase changes with liquids Evaporation… Liquid  Vapor (gas) Condensation… Vapor (gas)  Liquid

Equilibrium vapor pressure… When the rate of vaporization is equal to the rate of condensation, no net change in vapor pressure occurs. This is a dynamic equilibrium.

Temperature affects the rate of vaporization Increasing the temperature of a contained liquid increases the vapor pressure over the surface of a liquid.

Boiling Boiling occurs when the vapor pressure is equal to the external pressure. In Denver, where atmospheric pressure is low, boiling occurs at a lower temperature. In a pressure cooker, boiling occurs at a higher temperature.

Boiling point… the temperature at which boiling occurs. Normal boiling point is the temperature at which boiling occurs at 1 atm pressure (normal pressure). Boiling is also a cooling process.

The Nature of Solids The particles in a solid tend to vibrate about fixed points. They are not free to flow. Most solids are highly organized, dense and incompressible.

Melting point…. the temperature at which a solid turns into a liquid. Melting…. Solid  liquid Freezing… Liquid  solid

Solids Crystal Unit cell Allotrope Several forms of carbon Amorphous solids (glass, soot) Supercooled solids Network solids (diamonds, graphite)

Sublimation… the change of a substance from a solid to a vapor without passing through the liquid state. Sublimation… Solid  vapor Deposition… Vapor  solid

Phase diagrams Triple point describes the set of conditions where all three phases, solid, liquid, and gas, can exist in equilibrium with each other.

Phase diagram for water

Phase diagram for CO 2

Heating curve