Pearson Prentice Hall Physical Science: Concepts in Action Chapter 3 States of Matter

3.1 Solids, Liquids & Gases Objectives: 1. Explain how shape and volume can be used to classify materials 2. Describe how kinetic theory and forces of attraction can be used to explain the behavior of solids, liquids and gases

How Shape & Volume Classifies Materials Materials can be classified as solids, liquids, or gases based on whether their shapes and volume are definite or variable Solid: is the state in which materials have a definite shape and definite volume Definite means that shape and volume won’t change unless the material is acted on by an outside force

Liquid is the state of matter in which material has a definite volume but not a definite shape Liquids will take the shape of their container Gas: is the state of matter in which a material has no definite shape and no definite volume Gases will expand to completely fill the volume & take the shape of their container This Photo by Unknown Author is licensed under CC BY-NC-SA

Almost all matter exists as a solid, liquid or gas on Earth This is not true for the universe In places with the temperature of stars, matter exists in a state called plasma In 1995, scientists discovered a fifth state of matter called BCE (Bose-Einstein condensate) At temperatures close to absolute zero (0 K or -273ºC), BCE groups of atoms behave as if they were a single particle

Kinetic Theory Kinetic energy is the energy an object has due to its motion Kinetic theory says: 1. That all particles of matter are in constant motion 2. There are forces of attraction among all particles of matter

Kinetic theory of gasses says: 1. The constant motion of particles in a gas allows a gas to fill a container of any shape or size 2. Particles in a gas are in constant, rapid, random motion 3. The motion of 1 particle of gas is unaffected by other particles of gas unless they collide 4. Forces of attraction among particles of gas can be ignored under ordinary conditions

Kinetic theory of liquids says: 1. A liquid takes the shape of its container because particles in a liquid can flow to new locations 2. The volume of a liquid is constant because forces of attraction keep particles close together Kinetic theory of solids says: 1. Solids have a definite shape and volume because particles in a solid vibrate about a fixed point

Adding/taking Energy out of a system When you add energy to a system the particles begin to move faster As they move faster they collide and create friction (Heat) As they continue we get a phase change

Six Common Phase Changes phase change: is the reversible physical change that occurs when a substance changes from one state of matter to another Six common phase changes: melting, freezing, vaporization, condensation, sublimation, and deposition

Temperature, Energy & Phase Changes The temperature of a substance does not change during a phase change For example, water temperature remains constant when boiling to go from liquid to gas or when condensing from a gas to liquid

Energy is either absorbed or transferred during a phase change The amount of energy absorbed depends on the substance & is a unique physical property for each substance Definition: heat of fusion is the amount of energy absorbed when going from a solid to a liquid

Exothermic changes occur when energy is released to the environment An example of an exothermic change is water freezing since it releases its heat to the environment so that it can freeze Endothermic changes occur when energy is absorbed from the environment An example is water melting since it gathers as much heat as possible from the environment to melt

Melting & Freezing Water The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes Solid water (ice) has molecules in a fixed position that vibrate about a fixed point Freezing produces molecules in an orderly arrangement Liquid water has molecules that are attracted to each other and slide past each other due to special chemical bonds Melting allows a less orderly molecular arrangement

Evaporation & Boiling Vaporization is a phase change from a liquid to a gas Vaporization is endothermic since liquid water absorbs energy in the form of heat from the surroundings to go from liquid to gas Heat of vaporization is the amount of energy needed for a substance to change phases from liquid to gas Heat of vaporization is a unique physical property for each substance

Evaporation is the process that changes a substance from a liquid to a gas below the substance’s boiling point Evaporation is a process that takes place at the surface of a liquid and occurs at temperatures below the boiling point Vapor pressure is the pressure caused by the collisions of vapor on the walls of the container Vapor pressure increases as temperature increases

Q: How does surface area of a liquid affect the rate of evaporation? Definition: the boiling point is where vapor pressure equals atmospheric pressure Kinetic theory shows that as the temperature increases, water molecules move faster & faster until they have energy to overcome attractive forces of neighboring molecules Definition: condensation is the phase change from a gas or vapor to a liquid

Definition: sublimation is the phase change from solid to a gas without going through the liquid phase Example of sublimation is dry ice to CO2 at room temperature Definition: deposition is the phase change from a gas or vapor to a solid without going through the liquid phase Deposition is the reverse of sublimation Example of deposition is frost on windows

Phase Changes Diagram This Photo by Unknown Author is licensed under CC BY-SA