By Secundaria Digital

1. UNIT 2Energy

2. What is
energy?
 Energy is the ability of a system to do a work. It’s a physical
quantity which produces a change or an effect.
 The unit International System, the unit of measurement for
energy is the joule (J).There are other units:
1kJ = 1.000 J
1 Cal = 4,18 J
1kCal = 1.000 Cal = 4186 J
1 kWh = 3.600.000 J = 860 kCal
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3. Properties of
energy
 Energy can’t be created or destroyed.The law of conservation of
energy: the total energy of an insolated system remains constant,
it’s conserved over time.
 Energy can be transformed from one form to another. For
example, chemical energy from fuel is transformed into
mechanical energy in cars.
 Energy can be transferred from one body to another. For
example, when we hit a ball with racket, most of the mechanical
energy in the racket is transferred to the ball.
 Energy can be stored. For example, batteries store chemical
energy.
 Energy can be transported form one place to another. For
example, electrical energy is transported through electric cables.
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4. Forms of
energy (I)
 Chemical energy.This is stored energy contained in chemical
compounds (atoms and molecules). It is released during chemical
reactions.
 Electrical energy.This is the energy produced by the flow of
electric charge: matter is made up of atoms where there are some
even small particles called electrons that are constantly moving.
Their movement depends on how much energy is has. Humans
can force these moving electrons along a path from one place to
another.We generate electrical energy when we move these
electrons from one atom to other, with the use of magnetic forces.
 Thermal energy. It’s released as heat. Matter is made up of
particles or molecules that move (or vibrate) constantly.A rise in
the temperature of matter makes the particles vibrate faster.The
hotter the substance, the more its molecules vibrate, and the
therefore the higher its thermal energy.
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5. Forms of
energy (II)
 Electromagnetic energy. It’s stored in electromagnetic waves,
that can travel through vacuum.There are different kinds of waves
and all of them have different wavelenghts, properties and power,
and all interact with matter differently (changing its properties).
From less dangerous to more dangerous, they are: radio waves,
micro waves, infrared waves, visible light, UV waves, X waves and
Gamma waves.
 Mechanical energy. It’s the sum of:
 Kinetic energy. It’s enegy possessed by an object due to its motion.The
heavier a thing is, and the faster it moves, the more kinetic energy it
has.
 Potencial energy. It’s store within an object due to its position with
respect to some reference, normally ground. Any time that a heavy
object is kept high up, a force or power is likely to be holding up there.
This is why it stays up and doesn’t fall.The heavier the object is, the
more its potencial energy.
PE = m · g · h (J, kg, m/s², m) KE =
𝟏
𝟐
· m · v² (J, kg, m/s)
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6. Forms of
energy (III)
 Nuclear energy. It’s stored in the nuclei of atoms.
 Nuclear fission. In this process, the nucleus of an atom splits into two or
more parts, releasing a vast amount of energy.The two smaller atoms
don’t need as much energy to hold them together as the longer atom,
so the extra energy is released as heat and radiation.
 Nuclear fusion. In this process, the nucleus of an atom joins to other
nuclei to for a heavier atom. A vast amount of energy is also produced.
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7. Energy
resources
 Non-renewable energy resources: are limited energy resources
obtained from the Earth’s crust that have formed in the Earth
hundreds of millions of years.They are fossil fuels (coal, crude oil
nad natural gas) and uranium (nuclear fuel). Once consumed they
can’t be replaced.
 Renewable energy resources: energy resources which are
replenished continuosly and will not run out. Renewable energy
includes biomass, wind, hydro-power, geotermal, tidals and solar
sources.
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8. ¿Cómo se
genera le
energía?
(en español)
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9. Non-
renewabble
energy
resources:
advantages,
disadvantages
and uses (I)
TYPE ADVANTAGES DISAVANTAGES USES
COAL • Easy to
transport.
• Cheap
• Large reserves.
• Underground
coal mining is
dangerous.
• Combustion
• Damage to the
environment.
• Energy
• Heat
• Produce
steel.
PRETOLEUM • More efficient
than coal.
• Easy
transportation.
• Produces rain
and global
warming.
• High price
Agriculture,
plastics, tires,
pharmaceutic
als, dyes,
detergents,
and other.
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10. Non-
renewabble
energy
resources:
advantages,
disadvantages
and uses (II)
TYPE ADVANTAGES DISAVANTAGES USES
NATURAL GAS • Less harmful
than coal and
oil.
• Easy transport
• Abundant
• Cheaper than
electricity
• Toxic and
flammable
• Complex
processing
• Expensive
installation
• Electricity
• Heating
URANIUM • It produces a
lot of energy.
• No pollution
• It produces
radioactive
waste.
• Limited
• An accident can
release
dangerous
substances.
• Electricity
• Heat
• As weapon
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11. Renewabble
energy
resources:
advantages,
disadvantages
and uses (II)
TYPE ADVANTAGES DISAVANTAGES USES
BIOMASS • It produces little
wastes, which
also are
biodegradable.
• Less
contaminating
than fossil fuels.
• Most of it are
wastes of human
activities.
• Low energetic
performance
• Big volumen
in fresh state.
• Electricity
• Direct
combustion
• Charcoal and
liquid and
gaseous fuels
production
HYDRO • Low perfomance
• Cheap
• It doesn’t produce
waste or
contaminatings
• It helps to control
floods
• Expensive
transport
• It depends of
the weather
• It produces
big alterations
in the
environment.
• Dangerous
because of
dam breaking
• Electricity
• Distribute
water
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12. Renewabble
energy
resources:
advantages,
disadvantages
and uses (II)
TYPE ADVANTAGES DISAVANTAGES USES
SOLAR • Clean
• Cheap
• It depends of the
weather
• It can’t be storaged
• It requires much
terrain.
• Electricity
• Heat
wáter
WIND • Low cost
• High
perfomance
• It depends of the
weather
• Hard storage
• Dangerous for birds
• It requires much
terrain.
• Landscape
alterations
• Interference in
radio, tv, radars.
• Electricity
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13. Non-
renewabble
energy
resources:
advantages,
disadvantages
and uses (II)
TYPE ADVANTAGES DISAVANTAGES USES
TIDAL • Clean
• No wastes
• Ecosystem
alterations
• Limited to zones
with perfect
conditions
• Low energetic
performance
• Expensive
• Electricity
GEOTHERMAL • No wastes • Hard and expensive
localization
• Electricity
• Heating
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