18.1b Notes States of Matter & Phase Changes Supplement to Chapter 18

Objective  Describe the phase and energy changes associated with phase changes.

States of Matter SolidsLiquidsGases Mass Volume Shape Energy

Solids  Solid – holds a particular shape & has definite volume  Orderliness of particles  Mass: definite  Volume: definite  Shape: definite  Energy: low

Liquids  Liquid – does not hold own shape but does occupy a definite volume  Flows freely and takes shape of container  Mass: definite  Volume: definite  Shape: shape of container  Energy: medium

Gases  Gas – no definite shape or volume  Expands to fill available volume of container  Mass: definite  Volume: can be compressed  Shape: shape of container  Energy: high

States of Matter SolidsLiquidsGases MassDefinite VolumeDefinite Can be Compressed ShapeDefiniteShape of container Shape of Container EnergyLowMediumHigh

Plasma  gas-like  made of atoms that have been ripped apart into ions and electrons  the sun is made of plasma, as is most of the matter in the universe  Plasmas are usually very hot, and you can keep them in magnetic bottles

Changes in State  A transition from one state of matter to another  Melting: solid to liquid  Freezing: liquid to solid  Vaporization: liquid to gas  Boiling: throughout the liquid  Evaporation: surface only  Condensation: gas to liquid  Sublimation: solid to gas

Changes in States Solid Liquid Gas Sublimation Melting Freezing Condensation Vaporization

Changing States - Melting  Solid becomes a liquid  Melting point = temperature at which a solid begins to melt  Heat of fusion = the amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point

Freezing  Liquid becomes a solid  Heat of fusion is also the energy released when a liquid freezes  The attractive forces are strong enough that the particles form an ordered arrangement

Vaporization  Liquid becomes a gas  Evaporation = when vaporization occurs at the surface of a liquid  Causes the temperature of the liquid to decrease

Boiling  Second way a Liquid becomes a gas  Occurs throughout the liquid, not just on surface  Boiling point = temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface  The heat of vaporization is the amount of energy required for 1 kg of the liquid at its boiling point to become a gas

Condensation  Gas changes to a liquid  The heat of vaporization is also the amount of energy released during condensation

In-class assignment/Homework