States of Matter Kinetic Molecular Theory: the idea that particles of matter are always in motion; this applies to all states of matter Used to explain properties of matter in terms of energy

Ideal Gas = hypothetical gas that perfectly fits all 5 assumptions of the Kinetic Molecular Theory : 1) Gases consist of a large # of particles that occupy a larger space with respect to their relative sizes thus gases can be easily compressed 2) Collisions b/t particles and walls are perfectly elastic ( = no loss of KE) 3) Gas particles are in rapid, random, constant motion 4) There are no forces of attraction b/t gas particles 5) Temperature of a gas depends on the average KE of the particles; directly proportional A gas that is always a gas - Doesn’t exist!

Characteristics of Gases Expansion: no definite shape or volume; fill any container, regardless of shape Fluidity: particles slide easily over one another; act like liquids, thus they are both fluids Low Density and Compressibility: volume can be decreased greatly Diffusion: since gases are always randomly moving, freely mix together with other gases Effusion: process by which gases move out of a small opening; molecules with low mass effuse more quickly than those with larger masses KE= ½ mv 2

Liquids Least common state of matter in universe; not so on Earth Operate at slim range of temps/pressures Volume, shape, density? Particles in constant motion, and closer than those of a gas (intermolecular forces)

Other Characteristics of liquids: Have a very high density when compared to gases; depends on temperature  lower temp…except for water Not easily compressed Easily diffuse in other liquids it can dissolve in d/t… much slower than it is in gases

Surface Tension All liquids exhibit surface tension = a force that tends to pull adjacent particles at a liquids surface together, decreasing its surface area to the smallest possible size; meniscus Results from… water shows high surface tension Capillary action = attraction of a liquid to a solid; rises in a small tube against gravity

Surface Tension Look at the picture below. The milk forms small droplets that resemble a crown. But why does this happen? Because of the surface tension of water, which keeps the droplets spherical.

Some terms: solid liquid gas MELTINGBOILING FREEZINGCONDENSATION 0ºC100ºC melting/freezing point boiling/condensation point (ice) (steam)(water) SUBLIMATION

More info on Liquids Vaporization – liquid to gas Evaporation – escape from a non-boiling liquid at its surface Boiling – vaporization through the entire liquid Freezing – physical change from liquid to solid through the loss of HEAT. Evaporation- a beautiful process.

Solids Particles in a solid are tightly- packed together due to attractive forces. Highly-ordered. Atomic/molecular motion is restricted, but it occurs. 2 types: 1) Crystalline: consists of crystals (orderly, geometric, repeating pattern) 2) Amorphous: particles are randomly arranged Sodium Chloride crystals Amorphous solid

Properties of solids Definite shape and volume Definite melting point (d/t addition of heat) High density and incompressible Low rates of diffusion

Crystals Arranged in a lattice structure Smallest unit of a crystal that shows the 3- D pattern of the lattice = UNIT CELL

Changes of State Phase = any part of a system that has a uniform composition and properties Condensation = process by which a gas turns into a liquid Vapor = a gas in contact with its liquid or solid phase

Vapor Pressure The pressure exerted by a vapor that is in equilibrium with its corresponding liquid Develops in a closed system Increase AKE, increase particles leaving liquid, increased pressure Volatile liquids evaporate easily d/t weak IMF

Vapor Pressure

Notes on Boiling Point BP = when vapor pressure equals atmospheric pressure Increase pressure, increase BP = pressure cooker Molar Enthalpy of Vaporization = amount of heat needed to vaporize 1 mole of a liquid at the liquid’s BP at a constant pressure; the stronger the attraction…. Vapor pressure is directly proportional to temperature

Freezing and Melting Definitions? What is the difference b/t freezing water and ice? Boiling water and steam?

Do Now Explain the importance and significance of this graph…

More Vocab Molar Enthalpy of Fusion = the amount of heat required to melt one mole of a solid (40.79 kJ/mol for water) Sublimation vs. deposition

Phase Diagrams graph of pressure vs. temperature that shows the conditions under which the phases of a substance would exist

Water Most abundant liquid on Earth; essential to life; most reactions take place in it IMPORTANT!!! Review its structure and properties…

Water