Bond types
Ionic bonds
• Bonds are formed by the transfer of electrons.
The charges hold the atoms together.
Covalent bonds
Elements share valence electrons to form the bond
Chemical reactions
• Chemical reactions is the breaking
and form of bonds.
• More heat: the faster reactions can
occur
• Exothermic: give off heat
• Endothermic absorb heat.
Balancing reactions
• The reactants and products must have the
same number of atoms. You can not change
the subscripts.
Balancing example
• Change the coefficient until all atoms are
equal
Equilibrium
• Where the forward reaction occurs at the
same speed as the reverse reaction. All
concentrations stay constant.
Fission, Fusion and Radioactive decay
Two molecule combine to make a larger
Molecule. The Sun Two Hydrogens combine to
make Helium
A larger molecule splits giving off energy
Nuclear energy
Radioactive decay
Type of Radioactive Particles
•
•
•
•
Alpha Particle: made of 2 protons and 2 neutrons
Charge = +2
Mass =
4
Least amount of energy of radioactive particles,
largest radioactive particle
• Stopped by a piece of paper
(diagram courtesy of the University of Michigan Student
Chapter of the Health Physics Society)
• Beta Particle: is an emitted electron
• Charge =
-1
• Mass =
.ooo5
• Beta particle is smaller
than an alpha particles
and move faster.
• Beta particles have more penetrating
power than alpha particle
• Sheet of aluminum foil will stop beta part.
(diagram courtesy of the University of Michigan
Student Chapter of the Health Physics Society)
• Strong force: is one of the strongest forces in
nature
• The strong force holds protons and neutrons
together
• Very strong at close distances. Very weak as
distance increases
• http://www.valdosta.edu/phy/astro/pl_shows/bh
_2001/bh/page5.html
• Half-Life: the amount of time it takes for a
half of a radioactive sample to decay
• Hydrogen 3 = 12.3 years
• Carbon 14 = 5,730 years
• Polonium 211 = .5 seconds
• Uranium 235 = 700 million years
• Carbon Dating: is used to tell the age of
plant and animals (organic compounds)
• Scientists look at the ratio of carbon 14
compared to carbon 12 in dead plants and
animals
• Only useful up to 50,000 years
Measuring Radioactivity
• Geiger Counter: is a device that counts
charged particles by producing an electric
current
• Gives off “click” sounds when radioactive
particles are detected
Energy
Comparison of active and passive solar
power.
• Passive solar power uses the heat and light
from the sun without using any collectors,
grids, or cells.
• Active solar power systems use focusing
mirrors and metal plates to capture the sun’s
energy. Solar radiation is absorbed by the
collectors and then transfers the heat to air or
water. Or photovoltaic cells produce
electricity.
Transforming Energy
• Law of conservation of Energy: energy is
neither created nor destroyed only
transformed.
• Some energy transformation is not useful for
us.
– Example: Power lines transform energy into heat.
Published January 27, 2011 | By Amanda Kaufmann
Fossil Fuels
• Formed by decay of ancient plants and
animals
• When burned they produce carbon dioxide
and water
• Petroleum,
• Natural Gas, and coal
Petroleum
• Fossil Fuel made of Hydrocarbons
• Produced by separating the liquid oil in a
process called Fractional distillation.
– Oil is pumped into the bottom of a tower and
heated. Materials rise to the top depending on
boiling point and are collected. Some are pulled
from the bottom, like asphalt.
– Other uses: Plastics, lubricants, asphalt
Natural Gas
• Composed mainly of Methane.
• Natural gas contains more energy per kilogram
than either petroleum or coal.
• Produces fewer pollutants than other fossil fuels
Coal
• Solid fossil fuel found underground
• One fourth of our energy comes from coal.
• Coal is formed from organic material
deposited in ancient swamps.
• Burning coal results in more pollutants
Generating Electricity
Coal generation
Simple Electric Generator
• When the coil is turned, the magnets cause
movement in the electrons within the coil.
The movement of
electrons causes
magnets
an electric current.
coil
Nuclear Power
• Energy is released when the nucleus of an
atom breaks apart. (Fission)
• Nuclear power plants produced 8% of all
power in 2003.
• There were 104 nuclear reactors at 65 power
plants in the US.
Convection, conduction and radiation
16.2 Heat & Thermodynamics
• There are 3 ways that thermal energy is
transferred from one object to another
– Conduction
– Convection
– Radiation
• Conduction: is a heat transfer when 2 objects
are touching (direct contact)
• There is NO transfer of matter
• Conduction works fastest with:
– Solids  Liquids  Gases
• The particles of liquids and gases are farther
apart than solids, therefore heat is not
transferred as quickly
• Thermal Conductors: are materials that allow
heat and electricity to pass through them
easily
– Metals
– Copper wire for electrical circuits, gold wire in
spaceships, pots & pans
– Low specific heat values
• Thermal insulators: are materials that DO NOT
allow heat and electricity to pass through
them easily
– Non-metals
– Wood, plastic, air, glass, fiberglass
– Protect items from heat and electricity
– High specific heat values
• Convection: heat transfer that takes place in fluids
(liquids and gases)
• HOT AIR/WATER RISES
• Convection Currents: currents in liquids or gases, these
currents transfer thermal energy (caused by difference in
density)
• Ex. Pavement, beaker of hot water, ocean currents,
weather patterns, wind
• Radiation: is the transfer of thermal energy
(heat) by waves through space
• Radiation happens through air and empty
space
• Ex. Sun, wood burning stove, fireplace,
candles
• All objects radiate thermal energy