Kinetic Theory

States of Matter

– Kinetic Molecular Theory

– Four States of Matter

– Thermal Expansion

Chapter 16 Lesson 1

Kinetic Molecular Theory

KMT

– Tiny, constantly moving particles make up all matter.

– The kinetic energy (motion) of these particles increases as temperature increases.

– These particles are colliding with each other and the walls of their container.

Four States of Matter

Solids – low KE - particles vibrate but

can’t move around

– atoms held tightly into place

– definite shape & volume

Four States of Matter

Liquids – higher KE - particles can move

around but are still close together

– indefinite shape

– definite volume

Four States of Matter

Gases – high KE - particles can separate

and move throughout container

– indefinite shape & volume

– move more quickly than particles that make up solids

Four States of Matter

Plasma – very high KE - particles collide with

enough energy to break into charged particles (+/-)

– gas-like, indefinite shape & volume

– stars, fluorescent light bulbs, TV tubes

Phase Changes

Heat of fusion-melting – solid to liquid.

– energy required to change a substance from the solid phase to the liquid phase at its melting point is known as the

– some attractive forces are broken

Freezing – liquid to solid

melting point = freezing point

Phase Changes

Heat of vaporization – energy required for the

liquid at its boiling point to become a gas.

– all attractive forces are broken

– EX: steam burns, sweating, and… the drinking bird

Heating Curves

Evaporation – liquid to gas below the boiling point

Condensation – gas to liquid

Heating Curves

Solid - KE

Melting - PE

Liquid - KE

Boiling - PE

Gas - KE

Phase Changes

Sublimation – solid to gas

– EX: dry ice, freeze drying, iodine

Phase Changes

Thermal Expansion

Most matter expands when heated & contracts when cooled.

Temp causes KE. Particles collide with more force & spread out.

EX: thermostats (bimetallic strip)

Heating Curves

Kinetic Energy – motion of particles

– related to temperature

Potential Energy – space between particles

– related to phase changes

Solid or a Liquid?

Amorphous solids and liquid crystals

– two classes of materials don’t react as expected when changing states.

– solids soften and gradually turn into a liquid over a temperature range

– lack the highly ordered structure found in crystals

– are typically long, chainlike structures that can get jumbled and twisted

The Strange Behavior of

Water Water molecules

– unusual in that they have highly positive and highly negative areas

– charged regions affect its behavior

– as the temp drops the particles move closer together

The Strange Behavior of Water

Freezing water molecules

– unlike charges are attracted to each other and line up so that only positive and negative zones are near each other.

– water molecules orient themselves according to charge, empty spaces occur in the structure.

– these empty spaces are larger in ice than in liquid water, so water expands when going from a liquid to a solid state.

Liquid Crystals

LCD

– flow during the melting phase similar to a liquid, but they do not lose their ordered arrangement completely.

– placed in classes depending upon the type of order they maintain when they liquefy

– are highly responsive to temperature changes and electric fields.

– ex: televisions, watches, clocks, and calculators