Transcript Chemical Energy

Chemical Energy
Energy that is released
via chemical reactions.
Often times release is
through combustion
such as energy
generation via coal
Another example is a
battery
Batteries
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3 Parts: Cathode (positive charge), anode
(negative charge) and an electrolyte
(substance with free ions (positively charged
atoms)
Reactions occur at the anode which release
electrons, they want to flow toward the
cathode.
But the electrolyte keeps the electrons from
flowing to the cathode.
If you create a closed circuit, and provide the
electrons an alternate path to flow to the
cathode, then they will follow that path.
Now the chemical reactions at the anode
change the anode and the electrolyte
chemical composition, and eventually they
can no longer occur. So the battery no longer
produces electrons and current.
When you recharge a battery ,you reverse
the flow of electrons through the battery
and reverse the the chemical process,
restoring the battery to almost its original
chemical state.
Leaky batteries
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Alkaline batteries-popular form of battery for
many devices
Uses potassium hydroxide, which is an
alkaline as the electrolyte, instead of
ammonium chloride or zinc chloride.
All three are acids and can corrode the outer
steel shell and leak.
In addition, as a battery is discharged,
Hydrogen as is formed, which increases the
pressure inside the battery. This can rupture
the seals on the ends of the battery or the
battery canister itself.
They create a crystalline structure on the
outside of the battery. It can cause oxidation
on copper leads and damages circuits.
A solution of water and baking soda or
vinegar can be used to attempt to clean
corroded contatcs.
Lithium ion batteries
• In these batteries, lithium
ions are extracted from the
anode and inserted into the
cathode to create a current.
• The electrolyte if often a
lithium salt in a solution of
ethylene carbonate
• Note: a lithium battery is a
different battery, it has a
lithium anode-these have a
longer lifetime and can
produce higher currents
and voltages.
Heat Energy
Energy associated
with the random
motions of the
molecules in a
medium.
Measured by
temperature
• Temperature Scales:
• Fahrenheit – based on the
height of liquid (often
mercury or alcohol) in a
glass tube.
• Celsius – another scale
using height of liquid in a
tube
• Kelvin-absolute scale
– True measure of energy
Fahrenheit
temperature scale
• Freezing point of water set
at 32 and boiling point set
at 212, so there is 180
degrees between them and
each degree is 1/180 of the
difference between these
two points.
Celsius
temperature scale
• Freezing point of water set
at 0 and boiling point set at
100, so there is 100
degrees between them and
each degree is 1/100 of the
difference between these
two points.
Kelvin
temperature scale
• O k is absolute zero. All
molecular motion stops.
• Interval set so that 1 k = 1 c
• So to convert from c to k
k=c+273
Mass Energy
• E = mc2
• Energy and mass are
equivalent
• C = 3 x 108 m/s.
• A big number and its
squared! So even if m is
small, E is big.
• A small mass, converted to
energy, gives a lot of energy!
Example
Electromagnetic
energy
•Light displays properties of both
waves and particles.
•Light is an electromagnetic wave-a
wave created by alternating electric
and magnetic fields.
•“Light” is more than just visible light,
it covers wavelengths from radio thru
Gamma rays
•Light is also a “particle” called a
photon.
•Photons have energy given by E=hν or
E=hc/λ. H is constant, c is the speed of
light , ν is the frequency of light and λ
is the wavelength of the light.
Conservation of Energy
• The principle of
conservation of energy
states that energy
cannot be created or
destroyed. But it can be
converted from one
form to another
• This idea of energy
transformation is at the
heart of energy
generation.
Energy Sources renewable vs nonrewnewable
• Renewable – can’t be
exhausted
• Solar
• Geo-thermal
• Tidal
• Wind
• Hydro
• Non-renewable-can be
exhausted
• Fossil fuels (oil, coal etc)
uranium
How much do we use?
• World energy
consumption
• US energy consumption
How much do we use?
How much do we use?
• Almost 95% of the energy we use comes from
non-renewble energy sources!
• One of these days we will run out, and then
what?
• What are some short and long term answers
to this question?
Fossil fuels
FOSSIL FUELS
• Carbon or hydrocarbons (a compound made of hydrogen
and carbon) found in the earth’s crust
• Formed from the bacterial decay of plant and animal life in
ancient (a few hundred million years ago) seas.
• The decomposing material was covered with mud and
sediment
• This increased the pressure and temperature on the
material and deprived it of oxygen.
• A variety of hydrocarbon molecules are created in solid,
liquid and gas states.
• The gas and liquid could travel through the porous rock and
collect in geological traps (rock features that prevent
further movement of the hydrocarbons).
Petroleum traps
Why is there oil in Texas?