Transcript Science League Competition

STATES OF MATTER:


Kinetic Theory- the tiny particles in all
forms of matter are in constant motion.
Kinetic Energy: energy of motion

SOLIDS:

The particles in solids:

Are packed together (often in an
organized pattern called a crystal lattice)
Are held together by strong forces
(therefore have high melting points)
Vibrate about fixed points


Crystal
 Solid
with atoms, ions or molecules
arranged in an orderly, repeating 3-D
pattern.
 Unit Cell- smallest group of particles within
a crystal that retains the shape of the
crystal
 Crystals are classified in to 7 systemsmost of which are square cubic or
rectangular cubic.
•Allotropes-
A molecular form of an element that
exists in 2 or more different forms in the
same physical state

Example: Solid Carbon
 GRAPHITE
DIAMOND
PENCIL
Widely spaced,
linked, hexagon.
Weak bonds soft

Each CARBON
atom is strongly
bonded to 4
other carbons
hard
BUCKEY BALL
60 carbons
attached
together like a
soccer ball.
Really flexible
Oxygen; O2 gas or O3 gas (ozone)
Carbon Allotropes
So far, it is just of theoretical interest. It is not used in any
products or manufacturing processes. One process
developed in the Chemistry Division at Argonne National
Lab produces smooth thin films of diamond from bucky
balls. These films are smoother than those produced by
any other method. This some day may be useful in
making wear-resistant coatings on things like machine
parts.
Amorphous solids
 lack
an orderly internal structure. Atoms
are randomly arranged.
 Examples:
rubber, asphalt, plastics
 Glasses:
 Amorphous
solids; super cooled liquids
 Cooled to a rigid state without crystallizing.
Does not melt at a definite temperature but
gradually softens. When broken it forms
jagged irregular edges.
Liquids
 Most
liquids are polar molecular
compounds. (polar: to have + and – areas)
 The
particles in a liquid:
 Are packed together (almost as closely as
a solid)
 Are
held together by weak attractive
forces*(therefore have low melting points)
 Slide
past each other (vibrate and spin in
fixed positions.
Intermolecular Forces
 Attractive
forces between molecules
 The positve end of one molecule is
attracted to the negative end of an
adjacent molecule.
 Weakest: London dispersion forces
 Stronger; dipole – dipole interactions
 Strongest; Hydrogen- bonding
GASES:Most gases are non-polar molecular
compounds





The particles in gases:
Are very far apart (gases are about 99.99%
empty space
Have no attractive forces (therefore have
extremely low melting points.)
Move very rapidly and in constant random
straight line motion.
Diffuse from areas of high concentration to areas
of low concentration (smaller lighter molecules
diffuse at a faster rate than larger heavier
molecules)
Perfectly Elastic Collisions
 Collisions
between gas molecules in which
no energy is lost
 (energy is transferred from one particle to
another)
Summation of States of Matter
Solids
Attractive
Forces
Very Strong
Liquids
weak
Molecular
Motion
characteristics
NONE
Bounce off each
other
Forces b/t
particles
Molecular
Packing
Gases
Very tight, close
Closely packed
99% empty space
Very far apart
Vibrate in place
Slide past each
other
Rapid, random straight
line motion
Ave. speed = 1000mph
Incompressible Nearly
Definite shape incompressible
Definite volume Indefinite shape
Definite volume
Compressible
Indefinite shape
Indefinite volume
Plasma

1. occurs at extremely high temperatures.
(millions of degrees Celsius) KE becomes great
enough to break molecules into atoms.
 2. At these temperatures electrons have been
removed from the gaseous atoms.
 3. The resulting fluid of bare nuclei (+ ions) and
free electrons is called plasma.
COLD PLASMA – 50,000K to 1,000,000K
 HOT PLASMA- “stars” 10,000,000 to
1,000,000,000K

Bose-Einstein

A Bose–Einstein condensate (BEC) is a state of matter of bosons
confined in an external potential and cooled to temperatures very
near to absolute zero (0 K or -273.15 °C). Under such supercooled
conditions, a large fraction of the atoms collapse into the lowest
quantum state of the external potential, at which point quantum
effects become apparent on a macroscopic scale.

This state of matter was first predicted by Satyendra Nath Bose in
1925. Bose submitted a paper to the Zeitschrift für Physik but was
turned down by the peer review. Bose then took his work to
Einstein who recognized its merit and had it published under the
names Bose and Einstein hence the acronymn.

Seventy years later, the first such condensate was produced by
Eric Cornell and Carl Wieman in 1995 at the University of Colorado
at Boulder NIST-JILA lab, using a gas of rubidium atoms cooled to
170 nanokelvin (nK)[1] (0.000000170 K or -273.14999983 °C). Eric
Cornell, Carl Wieman and Wolfgang Ketterle at MIT were awarded
the 2001 Nobel Prize in Physics in Stockholm, Sweden[2].
 When a system of atoms is cooled rather than bosons, the BoseEinstein condensate is then sometimes called a Super Atom.[3]
KINETIC ENERGY AND TEMPERATURE



TEMPERATURE AND ENERGY ARE NOT THE
SAME THING!!!
Temperature is a measure of AVE. Kinetic Energy
The higher the Temp, the greater the Kinetic
Energy

Kelvin temperature is directly proportional to
Average Kinetic Energy.
 Celcius vs Kelvin Scale;
Kelvin = °C + 273



A 1° increment on the Kelvin scale = 1° on Celcius
3x Kelvin Temperature = 3x Kinetic Energy
Absolute Zero = temp. all molecular motion stops
Temperature Scale Comparison
Celcius
Thirty is hot
Twenty is nice
Ten is cool
Zero is ice
Pressure
pressure – collisions of gas particles
with the surface of an object.
 Atmospheric Pressure – collision of “air
molecules with the surface of an object.
 Barometer – instrument measures the height of
 Gas
a column of mercury supported by air pressure
vacuum
atmospheric
pressure
(forces Hg
up the
eudiometer
. tube)
Normal atmospheric pressure
pushing on a mercury barometer
supports a column of Hg about
760 mm high = 1 standard atmosphere
barometric
pressure
1 atm = 760 mm Hg = 30 in Hg = 14.7 psi = 101.3 kPa
Measuring air pressure –Barometers
760mmHg
Eudiometer
Below sea level
Cave (2atm)
At sea level (1atm)
Higher than sea level
on Moon (0atm)
Barometer
Barometer
on Mt. top
on moon
atmosphere
100 miles
high
95% mcs
1st 5 mi.
Medford
Colorado
EARTH
Less
atmospheric
pressure
No
atmospheric
pressure
Boiling point – temperature at which the vapor pressure of
a liquid = external pressure
Can boil by: increasing temperature increases KE of mc’s
or decreasing external pressure  so mc’s already have
enough KE
As elevation increases, atmospheric pressure decreases so
boiling point decreases.
CHANGES OF STATE – PHASE CHANGES are phase
changes that ALWAYS involve energy changes.
Energy in = Endothermic (cools surroundings)
(melting)
evaporation or boiling
SOLID
LIQUID
GAS
(freezing)
condensation
Energy out = Exothermic (warms surroundings)
Melting, evap. and boiling are cooling processes
Freezing and condensation are warming process
Evaporation VS Boiling
Similarities
Differences
-- Both involve a phase change:
liquid  gas
-- evaporation only occurs at the surface
-- boiling occurs throughout the body of the liq.
-- both require energy
(boiling H20 requires 540 cal/g)
-- evaporation occurs below the boiling point
-- boiling occurs at the boiling point
-- both are cooling processes – mc’s with high KE escape, leaving slower, cooler ones behind
sublimation – the conversion of a solid to a gas without passing
through the liquid state
Substances with very weak intermolecular
forces are unable to hold molecules together so they
are able to spread apart, preventing them from having
a liquid phase, and forcing them to sublime.
Phase Diagram
Temperature
Boiling point
Heat of vaporization
Heat of fusion
----------------------
gas
liquid
Melting point
-------solid
Time
During a phase change there is no temperature change
because all of the heat energy is being converted into kinetic
energy as the motion of the molecules increases.
Phase Diagram
 Shows
the relationship between solid, liquid
and vapor phases in a sealed container.
Each sections shows a pure phase.
Equilibrium
2 phases existing at the same time at
a certain temp & pressure. (line
separating 2 regions.)
Triple Point
Only condition that allows all 3
phases to exist at the same time.
(where lines intersect)