Transcript The States of Matter CH 9
The Boring States of Matter CH11
Kinetic Energy E
K The energy an object has because of its motion.
Temperature is a measurement of average kinetic energy.
Kinetic Theory-
Tiny particles in all forms of matter are in constant motion.
Liquids vs. Gases
Liquids, the molecules are moving and touching.
They interact They take up less space than gasses They overall have less E
k
than a gas of the same substance Gases, the molecules bounce off each other, but do not stay in contact There is
very little interaction
between molecules They take up a lot of space
gas liquid Which of these 2 parts are compressible?
Can you “squish” the gas?
Can you “squish” the liquid?
Evaporation: conversion of a liquid to a gas
At the surface, there are a few molecules that have enough E k to escape to gas.
By
increasing the temperature
, more molecules will have the necessary E k and evaporation will occur faster than before.
The vapor pressure increases with more heat/ Ek
Average kinetic energy
Temperature is a measurement of average kinetic energy.
If a beaker of water reads 20 °C, do all molecules in the beaker have kinetic energy = 20 ⁰ C?
There is a broad range of kinetic energies. Most of the molecules are “around 20C”, but there are some significantly less energetic, and some significantly more energetic.
Solids
Salt crystal, atoms are in a set position Molecules in solids only vibrate in place, they do not slide past each other They interact in their FIXED position More dense than gas, and most liquids
Heating a solid
S L melting The vibrations increase If they vibrate enough, some of the bonds holding the solid together will break.
L S freezing L G vaporization (or evaporation) This is called the melting point.
G L condensation
Evaporation vs. Boiling point
Atm is pressing down on the surface
Solid to a Gas?…Sublimation
Dry ice, is a classic example of sublimation Solids also have a vapor pressure.
When vapor pressure is high enough, the solid will go to gas, without stopping at liquid.
This is called
sublimation.
Gas to a solid – DEPOSITION
Phase Transition names
Give the change of state for each term S L Melting L S Freezing L G G L Vaporization Condensation S G G S d Sublimation deposition
Ionic Solids
Strong forces between oppositely charged ions.
HIGH melting points HIGH boiling points Non conductors as solids, conductors while molten.
Often water soluble Depends upon attractive forces for each other and other molecules.
Molecular
Combination of 2 or more non metals 1.
2.
3.
Molecular substances have 3 important types of weak intermolecular forces Dispersion Forces Dipole Forces Hydrogen bonds Inter-molecular (between molecule) forces are weak.
Have low melting and boiling points Think Oxygen and Water They’re gases and liquids at room temperature Therefore easy to separate: Non-Conductors of electricity
Think of the electron cloud being agitated
Dispersion (London) Forces
Most common type of intermolecular force.
F 2
Caused by temporary induced- dipoles formed in adjacent molecules.
-188 -34 Cl 2 Br 2 I 2 59 184
All molecules have dispersion forces, the strength depends on 2 factors: *The # of electrons in the molecule As molar mass increases, dispersion forces become stronger, the boiling pt of non-polar molecules increases.
Dipole Forces
Electrically attractive forces between + and – end of adjacent polar molecules. Boiling points of N 2 O 2 -196C -183C NO -151C The Nitrogen Monoxide is slightly polar and therefore has weak dipole forces. This explains the relatively higher melting points.
Hydrogen Bonding
Unusually strong DIPOLE forces.
This is due to the very small Hydrogen atom’s Electronegativity difference with: F fluorine O oxygen N nitrogen The strongest of the ‘weak forces’ Water H 2 O bp = 100 C, H 2 S -61C
Putting it all together
How can you know if a substance will melt, or sublimate?
The transitions depend upon both pressure and temperature.
At a given Temperature T: At a low pressure, something might sublimate, at a higher pressure it would likely melt
Pressure
Phase diagram
solid liquid Triple point, all 3 phases exist simultaneously gas temperature
Triple point .006 atm .001C
Phase Diagram for Water
4
th
state of matter: Plasma
Plasma
Occurs at super hot temperatures Gas atoms are stripped of their electrons Mix of loose electrons, and + gas ions is called
PLASMA
Hot plasmas make up the stars, and can be 10 million degrees Not very relevant to HS Chemistry.
Maxwell-Boltzman Distrubution
At high T More molecules are in a higher energy state