Download Energy - Alvin ISD

Energy
• Chapter 16.1
• As the roller
coaster zooms
up and down the
track, the energy
changes btwn
kinetic and
potential energy.
Energy
• Energy comes in many different forms:
–
–
–
–
potential energy
kinetic energy
solar energy
nuclear energy
Uses of Energy
• We use energy everyday:
–
–
–
–
–
to cook
run vehicles
keep buildings warm/cool
communicate
to run the miniature factories (cells) in our
bodies
• What is energy?
Vocabulary Word
• energy: the ability to do work or produce
heat
• kinetic energy (KE = 1/2mv2) energy of
motion
• potential energy (GPE = mgh) energy of
position or composition
Energy is Conserved
• As water runs through
the turbines of the
hydroelectric plant,
some of the potential
energy is converted
into electrical energy
Energy is Conserved
• As wood burns in a
fire, some of its
potential energy is
released as heat
Energy is Conserved
• Energy is always changing forms, but the
total amount of energy does NOT change.
• Energy is conserved.
Vocabulary Word
• Law of conservation of energy: in any
chemical reaction or physical process
energy is neither created nor destroyed
(though it may change from one form to
another).
Chemical Potential Energy
• Chemical potential energy is energy stored
in a substance because of its composition
(position of its electrons).
• octane (C8H18) is a component of gasoline
Chemical Potential Energy
• potential energy in octane is from the
arrangement and strength of the bonds
• as octane burns, some of the energy is
converted to work to move the pistons and
some is converted to heat.
Vocabulary Word
• heat (q): energy flows from a warmer object
to a cooler object
Heat
• The warmer object gets cooler
• The cooler object gets warmer
• They will both continue to transfer heat
until both reach the same temperature
Vocabulary Word
• calorie: the amount of heat required to
increase the temperature of pure water by
1 oC
• Calorie: nutritional Calorie is equal to 1000
calories or 1kcal
Vocabulary Word
• joule: the SI unit for heat. 1 joule is equal to
0.2390 calories. 1 calorie is equal to 4.184
joules
Specific Heat
• Since 1 calorie (or 4.184 joules) is the
amount of heat to increase the temperature
of water by 1oC, the specific heat of water is
4.184 joules
Specific Heat
• Different substances
have different specific
heats
• Some substances
require less energy to
heat up (gold) and
others require a lot
(water)
Water
• Water has a very high specific heat.
• Large bodies of water (lakes, oceans...) can
absorb and release large amounts of heat,
that’s why the climate near a large body of
water is more stable.
Vocabulary Word
• specific heat: the amount of heat required to
raise the temperature of 1 gram of a
substance by 1oC
Heat Absorbed or Released
• The amount of heat absorbed or released by
a substance can be calculated using the
following formula:
q = c x m x T
heat = specific heat x mass in grams x change in
temperature
Energy
• The sun is an inexhaustible source of
energy.
• Why can’t the solar energy meet all our
energy needs?
Solar Energy
• Why can’t the solar energy meet all our
energy needs?
– only available during the day
– must be able to store (solar ponds)
– sodium sulfate decahydrate pools
(dissolve/recrystalize)
– photovoltic cells
Photovoltic Cells
• convert solar energy
directly into electricity