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Eight Grade Review
Part One
Matter
• Matter - anything that has mass and takes
up space.
• Can be classified as elements, compounds,
or mixtures
• Made up of atoms
• Exists as solids, liquids, gases, or plasma
Matter continued...
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Atom - building block of matter.
Always in motion.
Atoms of the same element are alike.
Electrons are negative
Protons are positive.
Compounds are two or more
elements chemically combined.
• Mixtures are physically combined.
Acidity and pH scales
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Acids release hydrogen ions. H+
Bases release hydroxide ions. OHpH ranges from 0 - 14.
7 is neutral
0 - 6 are acids; 0 is strongest
8 - 14 are bases; 14 is strongest
Equal strength acids and bases combine to
form salt and water; this is called
neutralization.
Periodic Table
• Periodic table is arranged in order of atomic
numbers.
• Atomic numbers refer to number of protons.
• Electrons always equal number of protons.
• Atomic mass is neutrons plus protons.
• Family/group/column are formed through
common properties.
• Rows/periods are formed through equal
number of electrons orbit levels
Periodic Table
More on the table...
• The staircase separates metals and nonmetals.
• Metals are on the left.
• Non-metals are on the right.
• Elements touching the staircase are called
metalloids and share characteristics of both.
• Atoms lose/gain valence electrons to
become stable.
• How many valence electrons does the noble
gas family have?
Bonding
• Covalent bonding is when elements share
electrons.
• Ionic bonding is when elements transfer
(lose or gain) electrons.
• If the element has eight valence electrons it
can not bond with another element.
• Polyatomic bonding is when both types of
bonding have occurred. (ex: water)
What type of bonding is this?
Balancing Equations
• How many atoms are in 2N O ?
• Law of conservation of matter states matter
can never be destroyed (what goes
in…comes out)
• Reactants are always on the left and the
arrow always points to the product.
• Balance this equation:
2
• H2 + O2 -----> H2O
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Mixture types
• Homogenous = looks the
same throughout; mixed well
• Heterogenous = visibly
different; least mixed
• Solution = something has
been dissolved.
• Colloid = usually cloudy.
Calvin….on life.
Nuclear Reactions
• Fission - splitting of the nucleus; produces
much waste (power plant)
• Fusion - joining of two nuclei; little waste
(the sun)
• Alpha - weakest form of radiation.
• Beta - 10x stronger than alpha.
• Gamma - strongest form of radiation.
Chemical Reactions
• Exothermic releases heat energy resulting in
a hot product.
• Endothermic absorbs heat energy resulting
in a cold product.
• Chemical reactions produce new substances
with new properties.
• Physical reactions allow you to get the
original substance back.
Energy
• Energy can never be destroyed nor
created…only changed from one form to
another.
• Energy -the ability to do work.
• Kinetic energy (motion) depends on mass
and velocity.
• Potential energy (stored or position)
• Sound is mechanical energy.
Heat
• Heat - through friction. More movement of
atoms equals more heat.
• No heat is added during a phase change.
• Absolute zero is the absence of movement;
only a theory and exists at 0 K or -273 C
• Heat is transferred through conduction,
convection, or radiation.
• Conduction - direct contact
• convection - heat rises and cool falls
• Radiation - through empty space.
Sound
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Sound - produced through vibrations
Travels in compressions.
Fastest in solids.
Reflection of sound is an echo.
Sound is used in ultrasounds and sonar
devices.
Light
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Can be absorbed, reflected, or transmitted.
Changes speed in different mediums.
Is an electromagnetic wave.
Absorbed by black objects.
Reflected by white objects.
Allows us to see colors.
Electromagnetic Spectrum
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Radio waves are weakest.
Gamma rays are strongest.
Visible light is the only form we see.
All travel at the same speed.
Frequency increases as form gets stronger.
Wavelength decreases as form gets
stronger.
Force and Motion
• Force is a push or a pull
• Measured in newtons.
• Causes objects to move, stop or change
direction.
• Speed is distance/time.
• Velocity is speed and direction.
• Weight is the pull of gravity on an object.
• Speed of gravity is 9.8 m/sec/sec
Newton’s Laws of motion
• 1st law - inertia…something
moving wants to keep
moving…something still wants to
stay still…unless acted upon by a
force.
• 2nd law - mass x acceleration =
force.
• 3rd law - for every action there is
an equal and opposite reaction
• Newton’s law of gravity= if it has
mass; it has gravity.
Simple machines
• Machine - a device used to make work
easier.
• Resistance is the flow against.
• Work input is always more than work
output due to friction.
• Wedge, pulley, inclined plane, wheel and
axle, screw, and lever are the simple
machines
Electricity
• Resistance is lowest when
the wire is cold; forms a
superconductor.
• Wire, load, source, and
switch are parts to a
circuit.
• Static electricity is the
build-up of electricity.
• Electromagnets are
strongest when the wire is
wrapped around more
times.