Matter & Energy Give me matter and motion, and I will construct the universe. Rene Descartes.
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Transcript of Matter & Energy Give me matter and motion, and I will construct the universe. Rene Descartes.
Matter & Energy
Give me matter and motion, and I will construct theuniverse.
Rene Descartes
ENERGY
It is important to realize that in physics today,we have no knowledge of what energy is.
Richard P. Feynman
When is expenditure of energy required?
* tossing a ball* lifting a rock* launching a rocket
When is expenditure of energy not required?
* Rocket coasting through space
Satellite orbitingEarth requires noexpenditure ofenergy.
Expenditure of energy seems torequire motion and force.
* Kinetic Energy (Energy of Motion)> Thermal (heat) energy
* Potential Energy (Stored Energy)> Elastic energy> Gravitational energy> Chemical energy> Electrical energy> Magnetic energy> Mass-energy
* Radiative Energy
Some Varieties of Energy
Kinetic Energy (KE)
Mass (m)
Speed (v)
* KE m
* KE v2
2mv2
1 KE
Heat & Temperature
Higher Temp. Lower Temp.
Conservation of Energy
Energy neither appears nor disappears. It may be converted from one kind to another, in whichcase the total amount of energy is unchanged.
Conservation of Energy + Mass
* Einstein: mass and energy are interchangeable
2mc E mass
(speed of light)2
* Total of mass + energy is what’s really conserved!
0.1 kg mass Energy
equivalent to detonating
1 million tons TNT(1 ‘megaton’)
MATTER
ATOMS
When it comes to atoms, language can be usedonly as in poetry. The poet, too, is not nearly so concerned with describing facts as withcreating images.
- J. Bronowski
Old Picture:
ElectronsorbitNucleus:
larger orbit moreenergy
(‘Bohr Atom’)
New Picture
Electron ‘cloud’
Distance from Nucleus
Pro
bab
ilit
y of
Fin
din
g E
lect
ron
lowest energy
next lowest energyor
or ornext lowestenergy
In 3-D
HydrogenEnergyLevels(1 electron)
Ground State
Excited States
SodiumEnergyLevels(11 electrons)
Atoms are usually neutral:
# protons = # electrons
Ions: atoms with one or more electrons added and/or removed
A chemical element consists of atoms with equal numbers of protons
Isotopes consist of atoms of an element with a different number of neutrons
#protons#neutrons
e.g.,Hydrogen 1 0 Deuterium 1 1 Tritium 1 2
Atoms can bind together in molecules
A molecule is the smallest unit of a compound
e.g., CO2, H2O, etc
Phases of Bulk Matter
• Solid
• Liquid
• Gas
• Plasma
Tem
per
atu
re
(Avg
. Kin
etic
En
ergy
)
Solid
Liquid
Gas
Plasma
Fully Ionized