ST Mid-Year Overview

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ST Mid-Year Overview
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Combustion

• The fire triangle illustrates the relationship
  between the three basic elements needed to
  establish fire oxygen (O2), combustible fuel (a
  form of C and H), and heat to initiate and
  sustain combustion.
• In the combustion process, oxygen oxidizes
  (combines with) carbon and hydrogen molecules as
  heat breaks chemical bonds during combustion.
  When vegetation is burned, heat is released in
  the form of thermal, radiant, and kinetic energy.
  Heat is supplied initially from an external
  source (lightning, matches, etc).
• The general chemical equation for a combustion
  reaction
• (C, H compound) O2 ? CO2
  H2O

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Law of Conservation of Mass

• For example, if you were told that 4 grams of
  hydrogen reacted with some oxygen to make 36
  grams of water then you could figure out how much
  oxygen must have been used by applying the law of
  conservation of mass.
•  If mass is conserved it means that the mass is
  always the same or does not change. The Law of
  Conservation of Mass applies to chemical changes.
  When considering a chemical change this would
  mean that the total mass of all of the reactants
  in the chemical reaction is equal to the total
  mass of products in the chemical reaction.
• BALANCED EQUATIONS ARE NECESSARY!
•  
•  
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Nitrogen Cycle bacteria convert! N2 ? NH3 ?
NO2- ? NO3- ? N2

• NITROGEN FIXATION N2 ? NH3
• NITRIFICATION NH3 ? NO2-
  (nitrites)
• NO2- ? NO3- (nitrates)
• NITROGEN absorption Plants absorb ammonium (NH4
  ) and nitrates (NO3-) from soil or water.

• ANIMALS MUST EAT PLANTS or EAT OTHER ANIMALS to
  obtain nitrogen.
• DECOMPOSITION wastes ? ammonium
  (NH4)
• DENITRIFICATION NO3- ? N2 for the
  atmosphere.

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Carbon Cycle

• - Photosynthesis plants
• 6 CO2 6 H2O energy ? 6O2 C6H12O6
• Animals (herbivores) eat plants or animals
  (carnivores).
• - Living organisms respire
• 6 O2 C6H12O6 ? 6 CO2 6 H2O energy
• Animals waste release CO2 CH4.
• Forest fires release CO2

• - CO2 dissolves in water and reacts with calcium
  to become calcium carbonate. The carbonate rock
  comes to the surface through volcanic activity.
• - Fossil fuels form from dead organisms that fall
  to the ocean floor and fossilize.

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Magnetism

• Straight wire conductors magnetic field. NORTH
  compass needles point the SOUTH pole.

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• Heat and Temperature

• Heat is the total energy of molecular motion in a
  substance while temperature is a measure of the
  average energy of molecular motion in a
  substance. Heat energy depends on the speed of
  the particles, the number of particles (the size
  or mass), and the type of particles in an object.
  
• Temperature does not depend on the size or type
  of object. For example, the temperature of a
  small cup of water might be the same as the
  temperature of a large tub of water, but the tub
  of water has more heat because it has more water
  and thus more total thermal energy.
• It is heat that will increase or decrease the
  temperature. If we add heat, the temperature will
  become higher. If we remove heat the temperature
  will become lower. Higher temperatures mean that
  the molecules are moving, vibrating and rotating
  with more energy.

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• Energy Resources

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NUCLEAR ENERGY

• FOSSIL FUELS
• Coal is crushed to a fine dust and burnt.
• Oil and gas can be burnt directly.

http//www.darvill.clara.net/altenerg/fossil.htmh
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TIDAL POWER - A huge dam (called a "barrage") is
built across a river estuary. When the tide goes
in and out, the water flows through tunnels in
the dam. - The ebb and flow of the tides can be
used to turn a turbine, or it can be used to push
air through a pipe, which then turns a turbine.

• WIND ENERGY
• We can use the energy in the wind by building a
  tall tower, with a large propellor on the top.
• The wind blows the propellor round, which turns a
  generator to produce electricity.

http//www.darvill.clara.net/altenerg/fossil.htmh
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sOLAR ENERGY1) Solar Cells (really called
"photovoltaic or "photoelectric" cells) that
convert light directly into electricity. 2)
Solar Furnaces use a huge array of mirrors to
concentrate the Sun's energy into a small space
and produce very high temperatures. 3) Solar
water heating, where heat from the Sun is used
to heat water in glass panels on your roof.
http//www.darvill.clara.net/altenerg/fossil.htmh
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• HYDROELECTRICTY

• A dam is built to trap water, usually in a valley
  where there is an existing lake.
• Water is allowed to flow through tunnels in the
  dam, to turn turbines and thus drive generators.
• Hydro-electric power stations can produce a great
  deal of power very cheaply.

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TIDES The Earth-Moon System

• Point A is the surface of the ocean nearest the
  moon point C is farthest from the moon point B
  is the center of the earth.
• The arrows in the top diagram pointing toward the
  moon represent the force of the moon's gravity at
  these three points. 
• Point A is attracted to the moon most strongly,
  point C least strongly, and point B at
  intermediate strength.
• The lines leading downward from each point show
  how each point would move under the influence of
  the moon's gravity. 

• Point A moves farthest toward the moon, B, not as
  far, and C least of all.  The result is as if the
  ocean were bulging out toward and away from the
  moon.  Thus, as the earth rotates under this
  bulge, any point on earth has two high tides and
  two low tides each day.

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Dont forget the mechanical and electrical
engineering topics!