Syst

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Système InternationaleSI Units
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• SI is a system of measurement used in science
  based on powers of 10.
• Units are given using a prefix a base unit

Prefixes Kilo- (K) 1,000 Hecto- (H) 100 Deka-
(D) 10 Base unit- 1 deci- (d) 0.1 centi- (c)
0.01 milli- (m) 0.001
Base Units Length meter (m) Mass gram
(g) Volume cubic meter (m³) or liters (L) Time
seconds (s) Temperature scale celsius
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To remember the prefixes

• King
• Henry
• Danced
• By
• Dirty
• Cow
• Manure

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Conversion 80cm _________meters 80cm x
1m/100cm 2000mm ___________meters 2000mm
x 1m/1000mm 2 Kg __________-mg 2Kg x
1,000,000mg/1Kg
0.8 m
2 m
2,000,000 mg
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800mL __________L 800mL x 1L/1,000mL 7,500
cg __________Kg 7,500 cg x 1Kg/100,000cg
0.8 L
0.075 Kg
K H D b d c m -You can also count how many
times you are multiplying or dividing by 10 and
then move the decimal point as necessary
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SI Practice Conversions 1)2,345 g
______________Kg 2)3,462 mL _____________DL 3)
6.2 Km ______________dm 4) 78 Hg
_______________Kg 5) 0.001 KL_____________L 6)
0.000005 Km _________mm 7) 520 cm
_____________m 8) 892.2 dm ____________Dm 9)
1,236,000mm³_________Km³ 10) 3.5 hours
___________seconds

1. 2.345 Kg
2. 0.3462 DL
3. 62,000dm
4. 7.8 Kg
5. 1L
6. 5mm
7. 5.2m
8. 8.922 Dm
9. 1.236 Km³
10. 12,600 seconds

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Elements, Compounds, and Mixtures
We can describe matter based on its physical and
chemical properties, but how do we organize it?
Pure substances- any form of matter made of
uniform particles Mixture- matter made of
multiple types of particles that are not
chemically bound
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Pure substances are split into two
categories Elements- pure substance made up of
only one type of atom -cannot be broken down
into simpler substances by physical or chemical
means Compounds- pure substance made up of
multiple types of atoms, chemically bound to form
particles called molecules
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Elements are all made up of different types of
atoms and organized according to their physical
and chemical properties on the periodic table.
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Compounds Compounds are made of chemically bound
elements, but their properties can be different
than the properties of the elements that make
them. dangerous elements can make harmless
compounds and vice versa
A type of molecule is always made up of the same
ratio of its component elements Examples- water
is always 2 Hydrogen atoms and 1 oxygen -table
salt is always 1 sodium atom and 1 chlorine atom
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Compounds can be broken down during a chemical
change. -Sometimes they need a catalyst,
sometimes they need an input of energy, and
sometimes they just degrade over time.
Eat a steak, its proteins are broken down into
amino acids (mechanical and chemical digestion)
then your body reassembles the amino acids into
other proteins (translation).
Can you come up with any other examples of
compound breaking down or being formed?
Glucose
Deoxyribonucleic acid
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How do we know when a chemical change has taken
place?
Often the appearance (texture, color, physical
state) can change. Other signs of change
include -heat -odor -fizzing and
foaming -sound -light
Unlike physical changes, chemical changes are
hard to reverse -You can undo some reactions by
chemical means, but most of the time it is
difficult
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Atoms Theory and Structure- Review
Atoms are the smallest unit of an element
Each element is made-up of a different type of
atom, distinguished by the number of the
different subatomic particles that compose them.
There are three subatomic particles that make-up
an atom Proton charge and large mass
(1amu) Neutron 0 charge and large mass
(1amu) Electron - charge and small mass
Protons and neutrons are found in the nucleus of
the atom and electrons orbit around it, in what
is called the electron cloud.
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Atomic Theory

• All substances are made of atoms, which in turn
  are made of smaller particles called electrons,
  protons, and neutrons.
• They can be divided or combined (difficultly)-
  nuclear fusion and fission
• Atoms of the same element will all have the same
  number of protons and electrons, but the number
  of neutrons and as a result the mass may vary
  (isotopes).
• Atoms do join with other atoms to form new
  substances (compounds)

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Chemical Reactions
Chemical reactions (chemical changes) occur when
compounds form or degrade.
This occurs as a result of chemical bonding, when
electrons are shared, gained, or lost during the
association of one atom with another
Do all of an atoms electrons take part in
chemical bonding?
No, usually only the valence electrons take part
in chemical bonding
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Valence electrons are the electrons on the
outermost energy level -an atom can have between
1 and 8 of them -atoms bond with other atoms,
gaining, losing, or sharing electrons, to get a
complete set of 8.
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Which groups of elements want to lose
electrons? Which groups of elements want to gain
electrons? Which groups will most likely share
their electrons?
There are different types of chemical bonds. The
type depends on whether electrons are transferred
or shared between atoms.
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Ionic Bonding
A type of bonding in which electrons are
transferred from one atom to another
Atoms are usually neutrally charged, having an
equal number of protons and electrons, but
during an ionic bond that number is no longer
equal.
In one of the bonding atoms, the number of
electrons is greater than the number of
protons. -they are negatively charged In the
other bonding atom, the number of electrons is
less than the number of protons. -they are
positively charged
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Charged atoms are called ions -positively
charged ions are called cations -negatively
charged ions are called anions
Does an ionic compound, made of one cation and
one anion, have a charge?
No, the atoms in the compound are now charged,
but the compound itself is neutral
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Ionic compounds bond together in rigid, geometric
structures or chrystals. -the actual shape in
which they form is called a chrystal lattice
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Identify the cation and anion in each of these
ionic compounds CaCl2 Ba K2S FeBr3 Cr2O3 KI
NaCl FeO KF FrBr
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Usually when an atom has more than one or two
electrons to gain or lose it cannot transfer its
electrons.
In these cases they will share electrons, forming
covalent bonds
Compounds formed of covalent bonds are called
molecules -a molecule is the simplest form of a
covalent pure substance
Organic compounds (anything containing carbon)
are all covalent. -glucose -starch -celullose
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You can diagram a molecule using an electron-dot
diagram or Lewis structure.

• Drawing an electron-dot diagram
• Write the element symbol of the largest atom
• Draw dots around it representing its number of
  valence electrons
• Try to space them evenly in groups of two
• Place the other atoms around it in a way that
  allows each atom to have 8 valence electrons (2
  for hydrogen).

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-A pair of electrons involved in a bond can be
represented using a bar. (single bond) -4
electrons involved in a double bond can be
represented using a double bar (double bond) -6
by a triple bar (triple bond)
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Other types of Chemical Bonding
There are two other types of chemical bonding,
metallic and hydrogen bonding
They do not result in new compounds like ionic
and covalent bonding. Instead they associate or
hold like atoms together.
Metals are usually very dense, meaning that their
atoms are very close together. As a result their
electron clouds overlap and their valence
electrons are allowed to move throughout the
substance.
Hydrogen, because it is so simple an atom, when
it binds with electronegative atoms (want to take
electrons) becomes slightly positive. It will
then associate with electronegative atoms of
other molecules, limiting how far apart the
different molecules can go without more energy.
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Metallic bonding gives metals some unique
properties, such as electrical conductivity,
ductility, and malleability.
Electrical conductivity- since the valence
electrons can move freely through metals, an
electric current (moving electrons) can also.
Ductility- ability to be drawn into
wire Malleability- ability to be hammered into
sheets
Basically, metal can be bent into any shape
necessary and can be used to direct electricity.
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As a result of hydrogen bonding, water molecules
tend to stick together.
This gives water molecules several unique
propertiesadhesion, cohesion, and surface tension
Adhesion- water molecules tendency to stick to
other objects Cohesion- water molecules tendency
to stick to each other Surface tension- water
molecules tendency to form a rigid surface at
the top of a liquid
These properties explain capillary action
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Signs of Chemical Reactions
Chemical reactions often give us physical
evidence that a reaction is taking place. Such
as Color change Precipitate formation (forming
a solid) Gas release (creating a gas) Heat
(energy release)
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Compounds are represented using chemical formulas
(e.g. H2O) and chemical reactions are represented
using chemical equations.
6 CO2 6H2O C6H12O6 6O2
Chemical equations tell you the chemical formulas
of all of the compounds involved and how many of
each compound is involved.
We know -the number of each compound -The kinds
of atoms involved -the number of each kind of atom
The compounds entering the reaction are called
reactants The compounds produced in the reaction
are called products
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The one BIG rule The atoms in the reactants much
equal the atoms in the products
The Law of Conservation of Mass -Mass (matter) is
neither created nor destroyed during a normal
chemical or physical reaction
As a result the atoms present before a reaction
must also be present after a reaction
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To balance equations and make sure that no matter
is lost or created, we use coefficients. -they
tell us how many of a particular compound is
involved in a reaction -By adding them to one,
two, or all of the compounds involved in a
reaction we can be sure that the same number of
atoms enter and leave a reaction.
CO2 H2O
C6H12O6 O2
6CO2 6H2O
C6H12O6 6O2
Balancing chemical equations is part of a branch
of chemistry called Stoichiometry
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Energy
Energy is the ability/potential to do work (move
matter).
When matter interacts energy is transferred back
and forth.
Something with a lot of energy could do a lot of
work Or To do a lot of work (moving something
massive), it requires a lot of energy
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Energy in Chemical Reactions
Iron reacts with oxygen to form rust. How come
your car doesnt spontaneously rust and fall
apart?
Plants bond carbon dioxide and water to make
glucose, why can they not do this without light?
How come, after you remove the initial flame from
a candle, it continues to burn?
The answer is energy energy is transferred,
released, or absorbed whenever chemical bonds
form or break
This causes some reactions to take place very
slowly, some to take place very quickly, some to
require a constant or initial input of energy,
and some to release energy to the environment.
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Energy is absorbed when chemical bonds break and
released when they form.
If a chemical reaction absorbs more energy
breaking up its reactants than its products
release while being put together, then the
reaction is called endothermic. -Endothermic-
heat enters -Endo- inside
Photosynthesis is an endothermic reaction -the
absorbed energy comes from the sun
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If a chemical reactions releases more energy
bonding its products than it absorbs breaking its
reactants, then the reaction is called
exothermic. -Exothermic- heat exits -Exo-
outside-exit
Cellular respiration is an exothermic
reaction -the energy released from breaking up
glucose fuels our bodies
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Some reactions will occur spontaneously without
any initial input of energy, but most of the
time, even exothermic reactions need an initial
input of energy to get them started.
The amount of energy a reaction needs to get
started is called activation energy
Exothermic reaction- heat energy given off by
products
Endothermic reaction- heat energy stored by
products
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The speed at which reactants break and products
form during a chemical reaction is called its
reaction rate.
Reaction rate is affected by how exposed the
reactants are to each other and the amount of
ambient energy to start the reaction.
To speed up a reaction Increasing the
temperature increases the amount of
energy Increasing the concentration of the
reactants, the surface area on which the can
react, adding a catalyst, or removing an
inhibitor increases how exposed the reactants are
to each other.
Catalyst- anything that lowers the activation
energy required to start and maintain a
reaction Inhibitor-anything that increases the
activation energy required to start or maintain a
reaction. -neither catalysts nor inhibitors are
chemically changed during a reaction
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Color Quiz

• Does a catalyst increase or decrease reaction
  rate?
• Black- increase orange-decrease

2) What is activation energy? Black-
energy needed to start a reaction Orange-
energy gained during a reaction
3) During an exothermic reaction, is the net
energy gain positive or negative? Black-
positive Orange- negative
4) During an exothermic reaction, the products
Black- absorb heat Orange-
release heat
5) During an endothermic reaction, is more heat
absorbed or released? Black- released
Orange-absorbed
6) Photosynthesis is an example of what type of
reaction? Black-endothermic
Orange-exothermic
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Energy associated with the motion and position of
objects is called mechanical energy. It is split
into two types, kinetic energy and potential
energy.
Kinetic energy is the energy of motion,
describing how an object moves. Potential energy
is the energy of position, describing the
potential an object has to move as a result of
its position in the universe.
Mechanical energy Kinetic energy Potential
Energy
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Kinetic energy depends on the mass of an object
and how fast it is moving (its velocity).
EK (1/2)mv2
E energy K type of energy M mass V velocity
Which value affects an objects kinetic energy
more, mass or velocity? (p.241 practice)
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Potential Energy comes in two forms, elastic
potential and gravitational potential.
Elastic potential energy is an objects potential
to spring back after being stressed
somehow. e.g- stretching rubber band, drawing
back a bow, compressing a spring
Gravitational potential energy is an objects
potential to move as a result of gravity (to
fall). It depends on the height of an object and
its weight (mass and force of gravity)
Eg mgh
E energy Gtype of energy M mass G
acceleration of gravity (9.8m/s²) H height
P.242 practice
It can also be given as Gravitational
potential energy weight x height
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When an object falls or an elastic is released,
its potential energy is converted into kinetic
energy, but the total amount of energy stays the
same.
When the ball hits the ground and stops moving,
its mechanical energy is gone. Where did it go?
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Energy that appears to be lost is really just
transferred into a new form. There are seven
forms of energy

• Mechanical energy-energy associated with motion
  and position
• 2) Thermal energy- energy associated with heat
  (vibration of particles)
• 3) Chemical energy- energy stored in chemical
  bonds
• 4) Electrical energy- energy associated with
  moving electrons
• 5) Sound energy- energy of vibrating objects
  moving in waves through matter
• 6) Light/radiant energy- energy moving through
  electromagnetic waves, can travel outside matter
• 7) Nuclear energy- energy stored in the nucleus
  of an atom and released during fission and fusion

We will talk in detail about heat, light, and
sound later
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Energy is converted from one form to another
constantly and is involved in nearly every event
or occurrence in the universe
Example Mechanical energy of water (kinetic),
transfers to a turbine that converts mechanical
energy into electric energy. A light bulb then
converts that electrical energy into radiant and
thermal energy that is transferred to the
particles in the room around the light. Your eye
receives the radiant energy and converts it back
into electric energy that travels through your
optic nerve and to your brain.
The purpose of a lot of the machines that humans
use is to convert energy from one form to
another. -the engine in a car converts chemical
energy in gasoline into thermal and kinetic
energy.
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Hydrotubine
Wind turbine
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The Law of Conservation of Energy says that
energy cannot be created or destroyed
-There is more energy in your food than you can
use as fuel to move. -There is more energy
gasoline than your car can use to move.
No machine or natural energy conversion is 100
effective, though, so where does the energy go?
Whenever an object moves, there is a force that
pushes in the opposite direction that resists its
motion. This force is called friction. The energy
wasted to overcome friction is converted into
thermal energy.
Thermal energy, waste energy, is released in
every energy conversion.
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How efficient a machine or process is depends on
how much energy is wasted overcoming
friction. The less thermal energy released during
an energy conversion, the more efficient it is.
The more energy efficient a process is, the less
fuel it needs in the first place.
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Energy Resources
Our energy resources on earth are split into two
groups, renewable and nonrenewable.
Renewable resources can be regenerated or provide
an unlimited supply of energy. e.g. biomass
(regenerated), wind, solar (unlimited supply)
Nonrenewable resources cannot be regenerated
under reasonable means. There is a finite supply
of them on earth. e.g. fossil fuels,
uranium -basically anything that comes from
mining
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Energy resource Advantages Disadvantages
Fossil fuels -High energy output -Easy to access and transport -Can be used to generate electricity and produce synthetic materials -are nonrenewable -produce smog -can produce acid rain -risk of spills
Nuclear -concentrated form of energy -no air pollution -produces radioactive waste -is nonrenewable
Solar -limitless source of energy -no pollution -expensive to harness on large scale -only useful in sunny areas
Water -is renewable -does not produce air pollution -requires dams, which distrupt ecosystems -only available near rivers
Wind -is renewable -relatively inexpensive -does not produce air pollution -only practical in windy areas
Geothermal -almost limitless source of energy -plants require little land -only practical near hotspots -produces waste water, which pollutes soil
Biomass -is renewable -is inexpensive -requires large areas of farmland -produces smoke
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Color Quiz
There is a limited supply of _______________
resources. Red- renewable Green-
nonrenewable Which is an example of a
nonrenewable resource? Red- wind Green- fossil
fuels Which is an example of a renewable
resource? Red- solar Green- uranium
(nuclear) Which force opposes all motion? Red-
friction Green- gravity A process that creates
a lot of heat as a biproduct would be called
energetically __________________. Red-
efficient Green- inefficient The form of energy
associated with the movement and position of
objects is ______. Red- mechanical energy Green-
chemical energy The biggest downside to
hydroelectricity is ________________. Red-
ecosystem damage Green- air pollution
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What is Temperature?
Temperature is the average of kinetic energy of
the particles in an object or area.
It tells you on average, how fast the particles
are moving (vibrating or bouncing around). -all
particles are moving at different speeds and in
different directions, so the temperature of a
whole object is just an average.
If something has a high temperature, its
particles are moving quickly. If something has a
low temperature, its particles are moving slowly.
Think about state changes Which has a higher
temperature -solids or liquids? -liquids or
gases? What changed to cause the solid to melt?
The liquid to vaporize?
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What is thermal expansion?
As objects increase in temperature and their
particles move more, they spread out. -the whole
object swells as a result.
This is called thermal expansion
Thermal expansion allows thermometers to work It
causes your doors to stick in the summer It
causes hot air to rise (if volume increases and
mass stays the same, density decreases) Buildings
built in places where the temperature changes a
lot have to be built with thermal expansion in
mind.
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How is temperature measured?
Temperature is measured on any of three scales,
Fahrenheit, Celsius, or Kelvin.
Fahrenheit is used in the U.S, but not in
science. Celsius is used internationally and in
science because it is based on the freezing and
boiling temperatures of water. Kelvin is also
used in science, but it is centered around
absolute zero.
Absolute zero- temperature at which all particle
energy motion stops. Particles have zero kinetic
energy. -There are no negative values in the
Kelvin scale, but there are in the Celsius and
Fahrenheit scales.
Converting from one scale to another F 9/5 C
32 C 5/9 (F-32) K C 273
0 C 273 K 32F
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What is the scientific meaning of the wordHeat?
Heat is the energy transferred between objects at
different temperatures.
When an ice tray is placed in the freezer, heat
is transferred from the water to the air in the
freezer. When the water loses enough heat
(energy) it freezes.
Heat is always transferred from the higher
temperature object to the lower temperature
object. -to make something cooler, you take away
heat, you dont add cold.
The greater the difference in temperature, the
faster heat is transferred. -think of heat as
rolling down hill, the greater the difference in
temperature the steeper the hill.
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When an object is heated, the energy is
transferred in the form of thermal energy.
An objects thermal energy is the total kinetic
energy of the particles in an object or area
vs Temperature, which is the average kinetic
energy of the particles in an object or area
Thermal energy depends on amount, temperature
does not.
Whether heat is transferred between two objects
depends on their temperatures not their thermal
energy.
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Some objects increase in temperature faster than
others.
How well they conduct thermal energy is called
thermal conductivity. -leather seats compared to
cloth seats in a car.
Objects that conduct thermal energy well have a
low specific heat.
Specific heat is the amount of energy needed to
raise the temperature of 1Kg of a material
1Celsius or Kelvin.
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Unlike temperature, heat cannot be measured. It
must be calculated.
Heat (joules) (specific heat) (mass -Kg)
(change in temperature- C or K)
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Heat can transfer from one object to another in
several different ways.
Radiation- the transfer of energy by
electromagnetic waves (e.g. light, infrared
etc.) -can transfer through empty space outside
of matter
Conduction- the transfer of energy through direct
contact of their particles -the hot pavement
conducts its energy into your bare feet.
Convection- the transfer of energy by moving
currents of water or gas -the cooling effect of
wind or moving water
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Materials that conduct thermal energy well
(usually with a low specific heat) are called
conductors. -they exchange heat quickly -e.g.
baking pan
Materials that do not conduct thermal energy well
(usually with a high specific heat) are called
insulators. -they do not exchange heat quickly
-e.g. oven mitt
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Most of the energy on earth comes from the sun
through radiation.
We can survive because the atmosphere lets some
forms of electromagnetic radiation through but
not others.
It allows light through but blocks most
ultraviolet light. -damage to the ozone layer
limits ability to do this
Greenhouse gases help keep that energy on earth
and limit how much bounces back out into space.
They act as a thermal insulator. -too few
greenhouse gases and half of the planet would
freeze over each night. -like wearing a
t-shirt in January -too many greenhouse gases
and the earth will over heat -like wearing a
sweatshirt and jacket in August
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Electromagnetic Radiation and Sound

• Waves

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What are waves?
They are disturbances caused by the movement of
energy, either through matter or through empty
space.
As a wave moves across the ocean, each water
molecule only moves up and down. They do not
flow all the way to the shore.
As kinetic energy passes from one particle to the
next, each particle performs the same motion
(like dominoes falling).
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If you are floating in a boat on the ocean, do
the waves carry you all the way to shore?
No, the energy makes the boat go up and down,
just like the water molecules, and then it
continues on.
What does a surfer have to do to catch a wave?
They have to paddle the same velocity as the wave
of energy is moving until it breaks and they can
let gravity carry them (like sliding down a ramp
that keeps growing).
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When energy is moving through matter, that matter
is called a medium.
Waves that can only travel when in a medium are
called mechanical waves.
e.g. sound waves, ocean waves, earthquake waves
Waves that do not need a medium to travel through
are called electromagnetic waves. They can
travel through matter, but they can transmit
energy without it.
e.g. light, microwaves, infrared, ultraviolet,
x-rays, gamma rays
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Not all waves follow the same path.
Some vibrate perpendicular (a right angle) to the
direction motion, called transverse waves -they
can vibrate up and down or side to side. -they
look like traditional ocean waves. -electromagnet
ic waves are all considered transverse waves,
while only some mechanical waves are transverse.
The highest point of a transverse wave is called
the crest And the lowest point is called a trough
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When particles vibrate forward and backwards in
the same direction as the wave is moving, it is
called a longitudinal wave. -they are made as
matter sequentially stretches and
squeezes. -stretching or spacing out particles
is called rarefaction. -squeezing particles
together is called compression.
Sound waves are all longitudinal waves.
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Waves are described by several key properties
Amplitude, wavelength, frequency, and wave speed.
Amplitude- how high or far a particle vibrates
from its rest position. -High energy waves lead
to greater amplitude
Wavelength (?)- the distance between the crests
or compressions of a wave. -High energy waves
have shorter wavelengths (waves are close
together).
Frequency (f)- number of waves in a given amount
of time -the unit used is usually hertz (1Hz
1wave/second)
Wave speed (v)- the speed at which one wave
travels. v (?)(f)
If given two of the following, wavelength, wave
speed, and frequency, you can solve for the third.
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What happens to waves when they collide with a
new medium or with another wave?
When interacting with another medium, waves can
reflect, refract, or diffract.
When multiple waves interact, we get interference.
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When a wave hits an object that it cannot
transmit through, it bounces back.
This bounce back is called reflection.
An echo is an example of a reflection.
The colors that you see are the wavelengths of
light being reflected back. -if you see black,
all colors are being transmitted and non is being
reflected -if you see white, all colors are
being reflected and non is transmitted.
A mirror reflects light without distorting it
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Why do we see rainbows after a sun shower?
As light passes through the water particles in
the air, it is bent. Different wavelengths
(colors) bend more than others, so they separate.
The bending of a wave as it passes from one
medium to another is called refraction.
As a wave passes through one medium to another,
its wavelength and wave speed can change, but its
frequency stays the same.
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How come we can hear around corners but cant see?
Diffraction is a waves ability to bend around an
obstacle.
Waves with long wavelengths diffract more than
shorter wavelengths.
Light barely diffracts at all High pitched sounds
diffract well Low pitched sounds diffract very
well
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What happens when two waves collide?
For the moment that they are passing through the
same space, we have something called
interference.
If two troughs or crests coincide, they add
together and appear as one big wave -Constructive
interference
If a crest passes the trough of another wave,
they take away from each other -Destructive
interference
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How do Noise Cancelling Headphones work?
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When outgoing waves and reflecting waves
interfere to create what look like static waves
(not moving), we say that they have produced
standing waves.
The frequency at which standing waves are
produced is called that objects resonating
frequency.
When one object vibrates near the resonating
frequency of another object, it can make that
other object start to vibrate as well.
Basically, one sound causes another object to
start making a sound -This is called resonance
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What is sound?
Sound is a longitudinal wave of energy created by
the vibration (oscillation) of matter that
travels through a medium.
Anything that is vibrating creates a sound, as it
compresses and rarefacts the air particles around
it. -we can only hear only hear the sounds of
waves from objects vibrating at certain
frequencies though.
As waves travel through the air and through our
ear, they cause hair cells attached to nerves to
move, which sends signals to our brain.
Different hair cells react to different frequency
sounds. If they are damaged by high amplitude
waves, we do not re-grow them.
Your hearing peaked the day that you were born.
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How fast do sound waves travel?
The speed of sound waves depends on the medium
they are traveling through.
The denser and warmer the medium the faster the
waves will travel.
At high altitudes, where it is cold, sound
travels slower than at room temperature.
It travels faster through liquids and even faster
through solids.
Mach 3 means 3x the speed of sound
If you put your ear to the ground, you can hear a
train coming well before you could if you were
standing.
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Pitch, Frequency, Amplitude, and Volume
The pitch of a sound (how high or low) depends on
the frequency of the waves. -high frequency
high pitch
The volume of a sound (loudness) depends on the
amplitude of the waves. -high amplitude
loud -adding energy to a wave increases its
amplitude -the loudness of a sound is measured
in decibels
Sounds over 120 dB can physically hurt
83
How do bats use sound?
The reflection of sound is called an echo.
Bats (and whales) use echoes to find objects and
navigate in a process called echolocation. -elect
ronic echolocation is called sonar. -an
ultrasound is a procedure where sound waves
beyond human hearing are used to find objects
inside the human body.
84
Sound waves experience interference constantly.
It can be either constructive or destructive.
Constructive interference makes sounds
louder Destructive interference makes sounds
softer
As an object approaches the speed of sound, the
waves get so close together that constructive
interference produces a wave with extremely high
amplitude called a shockwave.
The sound heard from a shockwave is called a
sonic boom.
85
Most notes made by instruments are actually made
up of several different waves at different
frequencies combining through constructive
interference. -the result is that notes sound
quality for that particular instrument.
When different frequency sounds from different
instruments or voices work together pleasantly,
we say that they are in harmony.
When they do not, it is cacophony.
86
What are electromagnetic waves?
They are waves of energy, made of both electric
and magnetic fields, that can travel either
through a medium or a vacuum.
What is an electric field?
The field energy associated with charged
particles (usually moving electrons).
What is a magnetic field?
The field of energy associated with moving
charged particles or inherently polar materials.
Sowhen charged particles move, they have both an
electric and a magnetic field.
87
The two parts of an electromagnetic wave vibrate
perpendicular to each other.
When charged particles vibrate they produce
electromagnetic waves.
88
How fast do EM waves travel?
Like all waves, EM waves change speeds when they
change mediums, but in a vacuum (without a
medium), they travel 300,000,000 m/s.
That is 186,000 miles per second Or 7.5 times
around the earth per second.
Nothing in the universe travels faster than
light. -It is considered a cosmic speed limit
There are theories regarding what would happen as
you approached the speed of sound that include
things like time travel and exponential mass
increase.
89
EM waves vary in wavelength and frequency.
The different types of EM waves (waves within a
certain range frequency or wavelength) are laid
out in a spectrum according to their frequencies
and wavelengths.
Low frequency, long wavelengths are one
side. High frequency, short wavelengths are on
the other.
90
In general, the shorter the wavelength/higher
frequency the wave the more dangerous it can be.
Radio waves- ? gt 30cm- television and radio
signals are carried by radio waves
Microwaves- 30cmgt?gt1mm-used in microwaves, cell
phones, and radar
Infrared waves- 1mmgt?gt 700nm- most heat,
especially from the sun, travels as infrared waves
Visible light- 700nmgt?gt400nm- all of the light
and color that we see
Long ?
Short ?
91
Ultraviolet waves- 400nmgt?60nm- caused skin
damage (mutates cell DNA) but allows cells to
produce vitamin D.
X-rays- 60nmgt?gt0.001nm- travels through most
materials, used to see inside people, bags, etc.
Gamma rays-0.1nmgt?- travels through most
materials, used to treat some cancers
The difference between x-rays and gamma rays is
based more on source than wavelength (usually
different types of radioactive material)
92
EM waves, just like any other wave, can reflect,
refract, and diffract.
Unless we are looking directly at a light source,
any time we see an object, we are actually seeing
the light reflecting off of it.
When light bounces off a smooth surface (regular
reflection) the different waves are still
arranged the same way, so the reflected light
looks the same as the source. -Mirrors
When light bounces off of a rough surface
(diffuse reflection), the different waves are
reflected in different directions, so you just
see a general mix of color. -Walls
93
When the energy from an EM wave transfers to
matter rather than being reflected or
transmitted, it has been absorbed. -Most light
sources emit a wide range of EM waves, the colors
we see are the ones that we not absorbed.
Walls and even the particles in the air reflect
light and send it in all different directions,
this is called scattering. -This is why you can
see even if you are not directly in a beam of
light.
Long wave length light diffracts better than
short wavelength light, so it doesnt scatter as
easily. That is why for most of the day, the sky
is a short wavelength color (blue).
94
Since light travels slower through air than it
does through a vacuum, and slower through water
than it does through air, when it hits these new
mediums at an angle it bends.
This is refraction.
Short wavelength light refracts more than long
wavelength light. -so violets and blues bend a
lot and red bends little.
This separation of colors creates rainbows.
95
Since EM waves have such short wavelengths, they
do not diffract well, but they do diffract.
This is why the edge of a shadow (penumbra) is
fuzzy and lunar eclipses make the moon look red.
Interference of light can take place, resulting
in brighter or dimmer light, but it is hard to
notice unless working with a light of only one
wavelength (one color).
96
Why do we see the colors that we do?
We see whatever wavelengths (colors) reach our
eyes, which is determined by how materials,
absorb, transmit, and reflect light.
Objects that transmit all colors without
scattering them are transparent. Objects that
transmit colors but scatter them are
translucent. Objects that do not transmit visual
light are opaque.
97
With opaque objects, we see whatever light is
reflected.
Transparent and translucent objects appear to be
whatever color they are transmitting. -a sprite
bottle looks green because it transmits mostly
green light and absorbs the rest.
A pigment is any material/chemical that controls
how a substance interacts with light and gives it
its color.
98
How do we see color?
There is a difference between primary colors and
primary pigments. -primary colors are the
wavelengths of light that can combine to produce
a full spectrum of colors (produce white
light). -primary pigments are the pigments/colors
needed to make pigments that absorb all the
different wavelengths of light (produces black
pigment). -mixing paints is mixing pigments.
Primary colors- green, blue, and red
Primary pigments- cyan, yellow, magenta
99
Electricity and Magnetism
100
What is electric energy?
How are charged particles different than neutral
particles?
Charged particles follow the law of electric
charges, which states that like particles with
like charges repel and opposite charges attract.
The force, whether attractive or repulsive, that
one particle puts on another is its electric
force. The area in which this force works is that
particles electric field.
101
Individual atoms and most compounds, in the
natural state, are neutral (have the same number
of electrons and protons).
If electrons are lost or gained, a substance
becomes electrically charged.
If objects rub together (friction) they can pass
electrons and become charged.
If a charged material touches an uncharged
material it can pass on electrons (conduction).
If a charged material goes near an uncharged
material its electric force can cause the
electrons in the uncharged material to shift and
create a charged area (induction).
Electrons move to try to balance the charge of
the system that they are involved in. They are
not created or destroyed. They are conserved.
102
Electrons will keep moving until they contact a
positively charged substance.
Substances that allow the free movement of
electrons are called conductors e.g. metal
(wires)
Substances that limit the movement of electrons
are called insulators e.g. rubber (wire
coating)
Compounds held together by ionic or metallic
bonds usually conduct electricity well. Covalent
compounds do not.
How much a substance opposes the flow of
electrons is called its resistance.
103
What is static electricity?
Static electricity is an electric charge when
electrons are not moving from one object to
another.
The clothes in the dryer rub together, build-up a
charge. When they stop moving, they stop passing
electrons. They now stick together because of
static electricity ( sock sticks to shirt)
Objects dont hold on to static electricity
forever, eventually the built-up electrons will
find some place to go. This is called electric
discharge.
104
Electric discharge could be small and
unnoticeable or large, loud, and bright.
Electrons could pass harmlessly to particles in
the air. Electrons could jump from your hand to a
friend or door knob. Electrons could jump from
cloud to cloud or from a cloud to the ground
(lighting).
As clouds move and build, they pass electrons and
a static charge can build-up. When these charges
jump from a negative cloud to a positive cloud or
from a negative cloud to the positive ground we
see and hear lightning.
I hope no one ever feels it.
105
Color Quiz

• Electricity is a build-up of which type of
  particles.
• Blue- charged Red- neutral
• Particles with the same charge
• Blue- attract Red-repel
• Electric charges can be built-up through
  conduction, friction, or
• Blue- induction Red- radiation
• The measure of how a substance allows electricity
  to pass through it is
• Blue-insulation Red- resistance
• Static electricity is different than current
  electricity because the charged particles
• Blue- do not move Red- do move

106
How can we describe the movement of electrons?
Electric current- The rate at which electrons
move passed a certain point. Measured in amperes
(amps) -Individual electrons dont usually move
very fast, but they will all start to move as
soon as that option is made available, so your
lights turn on quickly.
When a current flows in only one direction it is
called a direct current (DC). Current in
batteries. When a current alternates which
direction it flows it is called an alternating
current (AC). Current moving through the wires
in your house. -The direction alternates
because the charge at the source (turbine at
the power station) changes
107
Another way to describe electricity is voltage.
Voltage describes the gradient between the
positive and the negative charges. The larger
the gradient, the more energy the electric
current will carry and the faster its electrons
will move.
The batteries in a remote control have a voltage
of 1.5. The current running through your house is
120 V. Lightning varies but can be 100,000,000 V.
108
Static electricity cant do work. A current has
to be present, which means that there cant be a
point in the system where electrons get stopped.
A complete system or path through which electrons
can flow without stopping is called a circuit.
When you flip the switch on the wall, you
complete the circuit and allow the current to
flow. When you flip it again you break the
circuit and stop the flow of electricity.
109
There are two main types of circuits, series
circuits and parallel circuits.
Series circuits are simple, single loops.
Electrons all follow one path. -like cars going
around a race track.
Parallel circuits are more complex loops.
Electrons have multiple paths that they could
follow. -like roads around a city
If a series circuit is broken any device (load)
running on that current will stop functioning. If
a parallel circuit breaks, one or two loads may
be cut off, but electrons can find their way to
the others.
Your house is one large parallel circuit
110
Series circuit
Parallel circuit
111
Electric currents can carry a lot of energy and
be dangerous. What can you do to promote
electrical safety?
112
What is a magnet?
A magnet is anything that attracts iron (they
work with other metals too, but iron is the most
common).
Magnetic materials have constantly moving
electrons, the moving electric fields create
magnetic force, the attractive or repulsive
ability of a magnet. -All atoms have moving
electrons, but in magnets they move in a way so
that their respective magnetic fields add to each
other rather than cancel each other out.
Magnets also always have poles, opposite sides of
the object that have opposite magnetic forces.
113
The poles of a magnet are labeled by how they
interact with the magnetic field surrounding
earth. -The north pole on a magnet orients itself
towards the north pole. -The south pole on a
magnet orients itself towards the south
pole. -The North Pole on earth actually has the
opposite charge as the north pole of a magnet.
A compass is just a magnet allowed to spin freely.
114
What is an electromagnet?
Since an electric current is comprised of moving
electrons it has a magnetic field.
Electromagnets wrap coils carrying an electric
current into a tight bundle called a solenoid
that increases the strength of the magnetic
field. -the more moving electrons that can be
squeezed into an area, stronger its magnetic
field will be.
This interaction between electricity and
magnetism is called electromagnetism.
115
Describe some ways electricity is used
productively in your life?
What things can you do to ensure that the
electricity around you is safe?
116
Since we see light that is reflected not
absorbed, our eyes are adapted to recognize the
primary colors, red, green, and blue.
We have cones in the back of our eyes that send
signals through the optic nerve to our
brain. Each cone is adapted to receive either
red, green, or blue light.
117
If someone is color blind, or color deficient,
one or more of these cones does not function
properly.
It is an x-linked recessive disorder, which means
the genes controlling the proteins inside these
cones is on the X chromosome.
It is expressed most frequently in men and is
inherited from the mothers side of the family.
118
What kind of technology have people developed to
work with light (help us see)?