Transcript Science GHST Review

Science GHSGT Review
Physical Science
What is Physical Science?
Study of matter and energy
 Study of the physical world
 On GHSGT, physics and chemistry

Speed and Velocity
Speed = distance divided by time
s = d/t
 Units of speed = m/s
 Velocity = speed in a given direction
 Example:
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55 mph = speed
 55 mph north = velocity
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Distance versus Time Graph
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AKA
position
versus time
graph
Straight line
represents
constant
(uniform)
speed
Acceleration
Acceleration = rate at which velocity
changes
 Involves a change in speed OR direction
a = (vf – vi )/ t
 Units of acceleration = m/s2
 Example: 0 to 60 mph in 5 seconds
 For acceleration to occur a net
(unbalanced) force must be applied
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Distance versus Time Graph
Revisited
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Non-linear
graph
represents
acceleration
Parabola =
constant
acceleration
Forces
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Force = a push or a pull
Net Force = sum of all
forces acting on an
object
Free-body diagram
shows all forces with
vector arrows
Direction of force =
direction of acceleration
Friction is a force that
always opposes motion
Determining the Net Force
Newton’s 1st Law of Motion
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An object at rest will
remain at rest and
an object in
constant motion will
remain in constant
motion unless acted
on by an
unbalanced force.
Reason for
seatbelts
Newton’s 2nd Law of Motion
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Force = mass x acceleration
F = ma
Newton’s 3rd Law of Motion
For every action,
there is an equal
but opposite
reaction
 Examples:
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Punch a wall, it
punches back
 Rocket propulsion
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Gravity
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Gravity = attractive force between two objects
that have mass
Depends on mass and distance
Effects of Mass and Distance on
Gravity
Momentum
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Momentum is mass in motion
p = mv
To change an object’s momentum a
force must be applied
Conservation of momentum states that
momentum before a collision equals
momentum after
Energy and Work
The ability to do work
 Work = transfer of energy by applying a
force to move an object
W = Fd
where force and distance are in same
direction
 Both work and energy are measured in
Joules
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Examples of Work and No Work
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Hammer applies
a force to move
the nail in the
same direction =
WORK
Waiter applies a
force upward
while the tray
moves forward =
NO WORK
Types of Mechanical Energy
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Kinetic = energy of
motion
Potential = stored
energy due to position
Conservation of Energy
Conservation of Energy
Conversion of Energy
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Motor = converts electrical energy into
mechanical energy
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Motors make fans Move which is Mechanical
Generator = converts mechanical energy
into electrical energy
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Georgia Power use a Generator to provide
electricity
Power
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Power = rate at which
work is done
P = W/t
Measure in Watts
More work, less time
= More Power
Less Work, Long time
= Less Power
Heat Energy
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Heat can be transferred through:
Conduction = when objects touch
 Convection = when matter moves
 Radiation = in the form of waves
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Conductors = easily transmit energy
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Example: metals
Insulators = do not easily transmit energy
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Example: gases such as air
Light
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Light is a form of electromagnetic radiation (EM)
EM spectrum shows the forms of radiation in
order of increasing frequency and decreasing
wavelength
Color of Light
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We see different colors depending on the
frequency of light emitted or reflected
This is the reason blue flames are hotter than
yellow. Blue has a higher frequency so more
energy.
Refraction of Light
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Light waves travel
faster in air than in
water and slower in
glass than water.
More dense =
slower light
When light enters a
different medium,
speed changes and
it bends.
Bending of light due
to change in speed
= REFRACTION
Electricity
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Electrons carry a negative charge.
Lost electrons = positive charge
Gained electrons = negative charge
REMEMBER:
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Like charges repel
Opposites attract
An object can be charged through:
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Friction (rubbing two objects together)
Conduction (touching a charged object to an
uncharged object)
Induction (holding a charged object near an
uncharged object)
Electrical Circuits
SERIES
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Current flows in a
closed circuit
Ohm’s Law
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V = IR
Two types of circuits:
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Series (single path)
Parallel (poly paths)
PARALLEL
Electromagnet
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One can make an electromagnet with a nail,
battery, and wire
When current flows through the coiled wire, the
nail becomes magnetized.
Electromagnetic Induction
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Occurs when a current is produced by
moving a conducting wire through a
magnetic field
Fundamental Parts of the Atom
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Atoms are made of:
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Most of the mass is in the
nucleus (protons &
neutrons)
Atomic number = number
of protons
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Protons (+)
Neutrons (neutral)
Electrons (-)
Silver has 47 protons
Atomic mass = number of
protons + neutrons
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Silver has 61 neutrons
Periodic Table
Left of zig-zag line = metals
 Right of zig-zag line = non-metals
 Along the line = metalloids
 Groups/Families = columns; go up and
down
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Group number indicates # of valence
electrons
Rows/Periods = side to side
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Period number indicates # of electron
shells/energy levels
Groups to KNOW
Group 1 = alkali metals (so reactive never
found uncombined in nature)
 Group 2 = alkaline earth metals (less
reactive than alkali but more reactive than
most metals)
 Group 7 (sometimes 17) = halogens (very
reactive non-metals)
 Group 8 (sometimes 18) = nobel gases
(non-reactive)
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Acids and Bases
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pH determines how acidic or basic a solution is
pH 1-6 = acidic
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pH 7 = neutral
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Acids dissolve to release hydrogen atoms
Acid of pH 1 is much stronger than acid of pH 7
Examples: HCl strong, Citric acid weak
De-ionized water
pH 8-14 = basic
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Bases dissolve to release hydroxide ion (OH-)
Base of pH 8 is much weaker than base of pH 14
Physical versus Chemical Changes
Physical changes are when no new
substances are formed (i.e. phase
changes such as melting, freezing, boiling,
condensation, evaporation, sublimation)
 Chemical changes occur when new
substances are formed (i.e. rusting,
foaming, burning)
 Whether physical change or chemical
change, MASS IS ALWAYS CONSERVED
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Phase Change Diagram
Radioactive Decay
ALPHA DECAY
•Alpha and beta decay
result in transformed atom
•Gamma decay results in
same atom with release of
energy
BETA DECAY
GAMMA DECAY
Half-Life
Half-life is the decay of some unstable
isotopes at a consistent rate that can be
calculated.
 For example: Isotope X has a half life of
100 years, if I have 50 g of Isotope X, how
much will remain after 100 years? After
200 years?
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Good luck! You can do it!!!