CHAPTER 13

States of Matter

Kinetic Theory

Kinetic energy is energy due to motion.According to the kinetic theory, all matter

consist of particles in constant motion

Three Assumptions of the Kinetic Theory

1. The particles in a gas are considered to be hard small spheres with insignificant volume

No attractive or repulsive forces exist Independent motion

2. Rapid, constant, random motion Gases fill their containers They travel in straight-line paths

3. The collisions are perfectly elastic Energy Transferred without loss Total energy remains the same

Gas Pressure

Results from the force exerted by a gas per unit of surface area

Gas pressure is the result of simultaneous collisions of rapidly moving particles

If no particles, then no collisions, so no pressure

Gas Pressure

Atmospheric Pressure results from collisions of atoms in the air with objects

Decreases as elevation increases.

Ex. Climbing a mountain

A barometer measure atmospheric pressure

Units for Pressure

SI unit is Pascal (Pa) (this in now a base unit)

Standard Units 1 atm = 760 mm Hg = 101.3 kPa = 760

torr = 1 N/m2 = 14.7 psi

Have to convert between these units of pressure

Conversions

A pressure gauge records 460 kPa. What is the pressure in mmHg?

Practice Time!

Kinetic Energy and Temperature

Potential Energy = stored energy

As temperature increases, kinetic energy increases

As a substance cools, kinetic energy decreases

Kelvin

SI unit

The Kelvin temperature scale reflects the relationship between temperature and average kinetic energy

Based on absolute zero of O K – the point at which all motion ceases

Solid Liquid

Definite volumeDefinite shapeParticles close

togetherVibrate

Definite VolumeNo definite shapeParticles further

apart than solid Flow

States of Matter

Gas Plasma

No definite volume or shape

Far apart as possible

Gas-like substanceVery high

temperaturesAbove 5000C Charged particleEx. The sun

State of Matter

Melting Freezing

Solid to liquidIncrease in Kinetic

energy

Liquid to SolidDecrease in kinetic

energy

Changes in States of Matter (Phase Changes)

Sublimation Deposition

Solid directly to a gasKinetic Energy

IncreasesEx. Iodine, dry ice,

moth balls

Gas directly to a solid

Kinetic Energy Decreases

Changes in State

Vaporization Condensation

Liquid to GasKE increases

Gas to LiquidKE decreases

Changes in State

Review

Kinetic Energy Increasessolid liquid gas

Kinetic Energy DecreasesGas liquid Solid

Two Types of Vaporization

1. Evaporation – changes liquid to gases below boiling point

Cooling process

2. Boiling Point – when heated to a temperature in which particles have enough Kinetic Energy to vaporize

Terms

1. Normal Boiling Point – the boiling temperature of a substance at standard pressure

2. Vapor Pressure – measure of the force exerted by a gas above a liquid

Phase Diagrams

Shows the relationship among solid, liquid, and vapor of a substance

Gives the conditions (temperature and pressure) at which a substance exist as a solid, liquid or vapor