Eighth Grade Review

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Eighth Grade Review
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Matter is anything that has mass and occupies
space. All matter is made up of small particles
called atoms.
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Matter can exist as a solid, liquid, gas or
plasma
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Matter can be classified as elements, compounds,
and mixtures
The atoms of any element are alike but are
different from atoms of other elements
Mixtures also consist of two or more substances,
but the substances are not chemically combined.
. Compounds consist of two or more elements that
are chemically combined in a fixed ratio.
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Compounds

• Compounds can be classified in several ways,
  including
• acids, bases, salts
• inorganic and organic compounds. (All organic
  compounds contain carbon).

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Matter can be described by its physical
properties that include, but are not limited to,
shape, density solubility, odor, melting point,
boiling point, and color
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• Acids make up an important group of compounds
  that contain hydrogen ions. When acids dissolve
  in water, hydrogen ions (H) are released into
  the resulting solution. A base is a substance
  that releases hydroxide ions (OH) into solution.

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• pH is a measure of the hydrogen ion concentration
  in a solution. The pH scale ranges from 014.
  Solutions with a pH lower than 7 are acidic
  solutions with a pH greater than 7 are basic. A
  pH of 7 is neutral.

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Neutralization Equation
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Kinetic Theory of Matter
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Equal volumes of different substances usually
have different masses
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Matter can be described by its chemical
properties that include, but are not limited to,
acidity, basicity, combustibility, and reactivity
(including the ability to rust).
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Atoms of the same element are alike
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The atom is the basic building block of matter
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Atoms and molecules are perpetually in motion
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Dalton

• Chemical elements are made from atoms

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Thomson

• Electrons are around a positively charge pudding
  like substance.

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Rutherford

• The atom is mostly space, there is a positively
  charged nucleus in the center.

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Bohr

• The Bohr model is a model used to describe the
  atom but it does not depict the three dimensional
  aspect of an atom

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The electron cloud model represents our current
theory of the atom which shows that the electrons
are not in a fixed orbit but an electron cloud
Schrödinger
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Protons are positively charged, found in the
nucleus, and the number of electrons

• Neutrons are neutral particles and are found in
  the nucleus

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Electrons are negatively charged particles found
spinning around the nucleus
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Atomic Number

• The number of protons in an atom determines what
  element it is.
• Add or subtract even one proton from an atom of
  any element and you no longer have the original
  element in any form. Now you have a different
  element!

• It is also the number of electrons in a neutral
  atom
• Atomic mass is the average mass of all the
  isotopes of an element
• Neutrons can be determined by subtracting the
  atomic mass from the atomic number.

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Atomic Structure Isotopes- have the number of
protons but different number of neutrons

• How many neutrons in the following isotopes?
• Hydrogen 1
• Helium 4
• Lithium 6
• Sodium 22

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The number of electrons in the outermost energy
level determines an elements chemical properties
and chemical reactivity
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The information within the boxes on the periodic
table can provide you with the atomic symbol,
atomic number, atomic mass, state of matter at
room temperature
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The periodic table of elements is an arrangement
of elements according to atomic numbers and
properties
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Metals, nonmetals, and Metalloids
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Periodic Table Basics
Essential Question What are Horizontal Rows
called?
Answer PERIODS
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Electron Configuration

• The Period number is equal to the number of
  energy levels in an atom
• Remember The number of electrons
  are equal to the number of protons in a neutral
  atom

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What are Groups on the Periodic Table?
Essential Question Groups are also known as
Families of Elements. They share chemical
properties. WHY? Answer They have the same
number of valence electrons.
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Electron Configuration

• For Groups IA VIII the group numbers are equal
  to the number of outer shell electrons or valence
  electrons
• Group IA has ONE valence electron
• Group IIA has TWO valence electrons etc.

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Name that GROUP

• The Alkali Metals
• IA one outer shell
• electrons

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Name that GROUP

• The Alkali Earth Metals
• IIA two outer shell electrons

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Name that GROUP

• The Noble Gases
• VIIIA eight outer shell electrons (except
  Helium which has 2 but is FULL)

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Name that GROUP

• The HALOGENS
• The Salt Formers
• VIIA SEVEN outer shell electrons
• therefore Oxidation state?
• -1

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Name that GROUP

• The Transition Metals
• 3-12 usually 1 or 2 outer shell electrons
• Lanthanide and actinides all have 2 valence
  electrons

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Atoms react to form chemically stable substances
that are held together by chemical bonds and are
represented by chemical formulas

• C 02 CO2

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To become chemically stable, atoms lose, gain, or
share electrons
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Chemical Bonding
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When a metallic element reacts with a
non-metallic element, the metallic elements
atoms gain or lose electrons forming ionic bonds
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When two nonmetals react, atoms share electrons
forming covalent molecular bonds
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• Metal to nonmetal ionic bond
• Nonmetal to nonmetal covalent bond

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Recognizing chemical equations

• Combustion Reaction
• Organic gas and oxygen
• CH4 O2 CO2 H2O
• Combustion Reactions always have carbon dioxide
  and water as products

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When matter undergoes physical change, the
chemical composition of the substances does not
change.When matter undergoes a chemical change,
different substances are formed
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The Law of Conservation of Mass states that in a
chemical reaction, the starting mass of the
reactants equals the final mass of the products
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A chemical equation represents the change that
takes place in a chemical reaction

• In a chemical equation, the chemical formulas of
  the reactants are written on the left an arrow
  indicates a change to a new substance and the
  chemical formulas of the products are written on
  the right

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Chemical Equations

• The number of atoms on the left side of the
  equations must equal the number of atoms on the
  right side of the equation.
• The equation must be balanced using coefficients
  - a number placed in front of the molecule or
  atom
• He H2O CO2
• four atoms nine atoms
  six atoms

A subscript is the number behind the chemical
symbol, it never changes.
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Balancing

• H2 O2 H2O unbalanced
• Left side Right Side
• H2 O2 H2O balanced
• Left side Right side

H
H
H
H
O
O
O
O
H
H
O
H
H
O
H
H
O
H
H
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Balancing Simple Equations

• Aluminum Oxygen Aluminum
  Oxide
• Al O2 Al2O3
• Left side              Right side
• Al O2 Al2O3
• 2 Al O2 Al2O3
• Left side Right Side
• Al O2 Al2O3
• Left side Right side

Start over
Uneven number must be made even to balance
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Chemical reactions are classified into two broad
types ones in which energy is released
(exothermic) and ones in which energy is absorbed
(endothermic)
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Nuclear reactions produce a large amount of
energy but there are potentially negative effects
of using nuclear energy such as disposal of
nuclear waste, fission has more waste than fusion

• Fission (I break) breaks a radioactive nuclei
  into new products and energy (Nuclear power
  plant and atomic bomb)
• Fusion ( You make) takes 2 nuclei and fuses them
  into one (power of the sun and stars)

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Energy exists in two states potential and
kinetic

• Potential energy is energy stored in an object.
  Energy can be stored chemically or based on
  position.
• Kinetic energy is energy of motion. The amount
  of energy depends on the mass and velocity of the
  moving object

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Energy Transformations

• Energy in the form of heat is one of the
  by-products of most energy transformation

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Heat and Temperature

• Heat and temperature are not the same thing. Heat
  is the transfer of thermal energy between
  substances of different temperature. As thermal
  energy is added, the temperature of a substance
  increases.

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Kinetic Energy

• Temperature is a measure of the average kinetic
  energy of the molecules of a substance.
  Increased temperature means greater average
  kinetic energy of the molecules in the substance
  being measured, and most substances expand when
  heated.

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The temperature of absolute zero (-273 degrees
celcius/0 Kelvin) is the only situation where
theoretically there is no atomic/molecular motion
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The transfer of heat occurs in three ways
conduction, convection, and radiation
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There is no change in temperature during a phase
change only a change in heat energy (freezing,
melting, condensing, vaporizing, sublimation)
Heat of Vaporaization
Heat of Fusion
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Heat Transfers

• Heat engines
• Thermostats
• Heat pumps
• Refrigeration

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Sound

• Sound is produced by vibrations and is a type of
  mechanical energy. Sound travels in compression
  waves and at a speed much slower than light. It
  needs a medium (solid, liquid, or gas) in which
  to travel.

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Sound travels in compressional waves and at a
speed much slower than light
In a compressional wave, matter vibrates in the
same direction in which the wave energy travels
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Sound needs a medium (solid, liquid, or gas) in
which to travel

• Sound travels fastest in solids
• Sound travels a little slower in liquids
• Sound travels slowest in gas

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All waves exhibit certain characteristics
wavelength, frequency, and amplitude

• From A to f is a wavelength or from D to I is a
  wavelength

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Resonance

• The natural frequency of an object.

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As wavelength increases frequency decreases
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Reflection and interference patterns are used in
ultrasonic technology, including sonar and
medical diagnosis
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Light

• Light is a form of radiant energy that moves in
  transverse waves
• Transverse waves move at right angles to the
  direction the energy travels.

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• All transverse waves exhibit certain
  characteristics wavelength, crest, trough,
  frequency, and amplitude. As wavelength
  increases, frequency decreases.

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There is an inverse relationship between
frequency and wavelength

• As wavelength increases, frequency decreases

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Light travels in straight lines until it strikes
an object where it can be reflected, absorbed,
refracted, or transmitted

• Mirrors, opaque, translucent, and transparent
  materials

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As light waves travel through different media,
they undergo a change in speed that may result in
refraction (bending of the wave).
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Mirror images

• Images in convex mirrors Images in
  concave mirrors
• are always smaller
  are always bigger (close)

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Lens images
                         

• Convex lens
• Concave lens

                         
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Electromagnetic waves are arranged on the
electromagnetic spectrum by wavelength
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All types of electromagnetic radiation travel at
the speed of light but in different wavelengths
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Radio waves are the weakest energy and have the
longest wavelength and the lowest
frequency.Gamma rays are the strongest energy
waves and have the shortest wavelength and the
highest frequency

• Visible light lies between infrared and
  ultraviolet waves and makes up only a small
  portion of the electromagnetic spectrum (ROY G
  BIV).

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Several factors affect how much electricity can
flow through a system Resistance is a property
of matter that moves against the flow of
electricity and thus some substances are more
resistant than others
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Friction can cause electrons to be transferred
from one object to another. These static charges
can build up on an object and discharge slowly or
rapidly
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• Electricity can produce a magnetic field and
  cause iron and steel objects to act like magnets.
• Electromagnets are temporary magnets that lose
  their magnetism when the electric current is
  removed
• The strength of an electromagnet depends on the
  number of wire coils wrapped around the iron core

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Both a motor and a generator have magnets (or
electromagnets) and a coil of wire that creates
electricity
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• A conductor is a material that transfers an
  electric current well. An insulator is material
  that does not transfer an electric current. A
  semiconductor is in-between a conductor and an
  insulator.

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• The diode is a semiconductor device that acts
  like a one way valve to control the flow of
  electricity in electrical circuits.
• Solar cells are made of semiconductor diodes that
  produce direct current (DC) when visible light,
  infrared light (IR), or ultraviolet (UV) energy
  strikes them.

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• Light emitting diodes (LED) emit visible light or
  infrared radiation when current passes through
  them. An example is the transmitter in an
  infrared TV remote or the lighting course behind
  the screen in an LED TV or notebook computer
  screen.

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• Transistors are semiconductor devices made from
  silicon, and other semiconductors. They are used
  to amplify electrical signals (in stereos,
  radios, etc.) or to act like a light switch
  turning the flow of electricity on and off.

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Motion

• Acceleration is the change in velocity per unit
  of time.
• An object moving with constant velocity has no
  acceleration.
• A decrease in velocity is negative acceleration
  or deceleration.

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• A distance-time graph for acceleration is always
  a curve. Objects moving with circular motion are
  constantly accelerating because direction (and
  hence velocity) is constantly changing

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Speed is the distance per unit of time.Velocity
is speed in a given direction
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Newton identified three laws that describe the
motion of all objects
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Newtons First law states that an object in
motion (or at rest) will remain in constant
motion (or at rest) unless it is acted on by an
outside force
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Newtons Second law states that force equals mass
times acceleration (Fma)
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Newtons Third law states that for every action
force, there is an equal and opposite reaction
force
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Weight is a measure of force due to gravity on
the mass of an object
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Force and Motion

• A force is a push or pull. Force is measured in
  newtons. Force can cause objects to move, stop
  moving, change speed, or change direction. Speed
  is the change in position of an object per unit
  of time. Velocity may have a positive or a
  negative value depending on the direction of the
  change in position, whereas speed always has a
  positive value and is non-directional.

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Work is the force required to move an object over
a distance

• Simple machines have different purposes to
  change the effort needed (mechanical advantage),
  to change the direction or distance to which the
  force is applied, to change the speed at which
  the resistance moves, or a combination of these
• Simple machines make work easier

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Work Output

• The work put into a machine is always greater
  than the work output due to friction.
• The ratio of work output to work input is called
  efficiency

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Formulas

• Speed distance/time (s d/t)
• Force mass acceleration
• (F ma)
• Work force distance (W Fd)
• Power work/time (P W/t).

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Dont you feel fabulous?

• Repeat after me. I am as smart as a sixth
  grader, I am as smart as a seventh grader, I am
  as smart as an eighth grader..
• I will do fabulous on the SOL!!!!!!!!