Do Now:•Compare solids, liquids, and

gases.

•At room temperature, why is water typically found as a liquid, carbon dioxide as a gas, and carbon as a

solid?

http://www.harcourtschool.com/activity/states_of_matter/

Solid Liquid Gas

Not very compressible

Not very compressible

Highly compressible

High denisty High density Low density

Definite volume Definite volume Fills container competely

Retains its own shape

Assumes shape of container

Assumes shape of container

Motion limited to vibrational movement

Slow diffusion – particles can slip past each other

Rapid diffusion

Low expansion on heating

Low expansion on heating

High expansion on heating

Why are the properties of each state so different?

Force of attraction between atoms, ions, or molecules. A solid has the strongest attractive forces, a gas has the weakest (negligible) attractive forces.

Gases…

• What are some unique properties or physical behaviors of gases that differ from the other states?

To help us understand gas behavior we can use

• The Kinetic Theory

• a model• states that all forms of matter are made up of tiny particles that are in constant motion

Kinetic Molecular Theory

1. A gas consists of small particles that have mass.

2. The particles are far apart from each other (volume of gas molecule is insignificant).

3. No attractive or repulsive forces exist between the molecules.

Kinetic Molecular Theory

4. Gas particles are in constant, rapid and random motion. They move in straight paths and fill their container

5. Collisions of gas particles with each other or with the walls of the container are perfectly elastic. Kinetic energy is conserved.

When gas molecules collide with other molecules, their container, or any

object…• They apply a force over an area

PRESSURE!

Pressure units

• Pascal (SI unit) = 1 N/m2

Other pressure units…

• kPa

• atmospheres

• mm Hg

• psi (lb/in2)

Atmospheric Pressure

• Force exerted on you by the weight of tiny particles of air (air molecules).

• Air molecules are moving, collide with things, apply force per area … Pressure!

• Standard atmospheric pressure is 760 mmHg or 1 atmosphere (1 atm)

• It is dependent on elevation. At high elevation, air pressure is lower.

Atmospheric Pressure can be measured with a barometer

Does mercury have to be used?Can water be used?How would the barometer and pressure reading be affected?

What does temperature measure?

• The average kinetic energy of the molecules

Absolute Scale

• Must be used to describe kinetic energy of molecules and their motion

• ºC (Celsius) + 273 = K ( Kelvin)

Liquids

• Particles are attracted to each other (has a definite volume)

• Particles are free to move past each other (liquid flows) in addition to vibrating

• These movements contribute to the average kinetic energy of the molecules.

Compare evaporation and boiling

• Vaporization ( liquid > gas)• Evaporation occurs at the

surface.• Boiling occurs in the body of

the liquid. Depends on atmospheric pressure.

Water molecules at the surface overcome IM forces and escape into the vapor phase

Gaseous molecule will collide with the liquid surface and if kinetic energy sufficiently low it will be captured and return to liquid phase

Dynamic Equilibrium

Vapor Pressure

EVAPORATION (a surface phenomenon)

Boiling• Boiling point of a liquid is the temperature at

which the vapor pressure of the liquid equals the atmospheric pressure surrounding the liquid

•Normal Boiling Point

•the temperature at which a liquid's vapor pressure equals one atmosphere (standard pressure)

Solids• Crystals – rigid body where particles

are in a highly ordered, repeating pattern.

• They are seven crystal systems classified by shape

•Unit cell is the simplest repeating unit that generates the crystal

Some arrangements of atoms…

What keeps • Salt, NaCl, together?

• Lead, Pb, together?

Ionic compounds are held together by ionic bonds, positive ions attracted to negative ions

Metals are held together by metallic bonds, sharing of valence electrons among fixed positive ions

-- -++

Network Crystal

Carbon• Graphite

• Diamond

Solids that contain strong directional covalent bonds to form a solid that might be viewed as a “giant molecule”.

Allotrope – form of an element differing in crystal or molecular structure

Diamond

• Hardest naturally occuring substance

• Used in industrial cutting implements

Graphite

• Slippery (used as a lubricant)

• Conductor of electricity

• Pencil “lead”

Fullerene (aka Buckyballs)

• Discovered in 1985

• Named after Richard Buckminster Fuller, an architect, who designed geodesic domes

• The basic C60 structure consists of 60 carbon atoms that link together to form a hollow cage-like structure.

Amorphous Material•Substance that lacks order•Does not have a sharply defined melting point•As heated, gradually softens and flows•Upon cooling, it flows more and more slowly

Viscosity (resistance to flow) increasesExamples: Glass and butter

Do Now:

Solid

Liquid

Gas

Name each phase change. Indicate if endothermic or exothermic process

Phase Diagram