Transcript 8th Grade Science Final Exam Review

8th Grade Science
Final Exam Review
1. What are the tests used to
identify a mineral?
 Streak – color of a mineral’s powder.
 Fracture – splitting a mineral apart unevenly.
 Cleavage – breaks evenly.
 Luster – describes how light is reflected from a mineral’s
surface.
 Density – mass/volume
 Hardness – Moh’s Scale (Talc = 1: Diamond = 10)
2. What is a crystalline structure and
how does it relate to minerals?
 A repeating pattern of a mineral’s particles.
 All minerals are crystalline.
3. What are the properties of minerals?
Give two examples of minerals.
 Natural.
 Inorganic – no materials were part of living things
 Solid
 Crystalline – repeating inner structure with the same
chemical composition throughout.
Quartz
Halite
4. Describe the three types of rocks, how
they form and an example of each.
 Sedimentary – sediments compacted together.(Sandstone)
 Metamorphic – change due to intense heat/pressure(Marble)
 Igneous – form from the cooling of magma(Granite)
Sandstone
Marble
Granite
5. Coarse-grained and fine-grained rocks
form differently. Explain the difference.
 Coarse-Grained = cools slowly(Granite)
 Fine-Grained = cools quickly(Basalt)
Basalt
Granite
6. Draw the rock cycle. Why do there
need to be multiple sets of arrows?
7. What is the difference between an
earthquake and an aftershock?
 Earthquake – the main earthquake that happens first
 Aftershock – smaller earthquakes that occur in the same
focus days to years after the main event.
8. What is the difference between the
epicenter and focus of an earthquake?
 The earthquake’s focus is the point within the earth where the
earthquake originates.
 The epicenter of an earthquake is the point on the surface of
the earth directly above the focus.
9. Describe the Richter Scale in terms of values
and how it’s measured.
 Measures the amount of energy released by an earthquake.
 Measured using distance from the epicenter and wave
amplitude.
10. What are the three types of plate
boundaries? How do they interact?
 Divergent = plates separate
 Transform = plates slide past one another
 Convergent = plates collide together
 Continental-Continental = push up and form mountains
 Continental-Oceanic = collide and form volcanic mountains
 Oceanic-Oceanic = collide and forms volcanic islands
11. What geological features are found
where the following types of crust collide
?
 Continental-Continental = mountains
 Continental-Oceanic = Volcanic Mountains
 Oceanic-Oceanic = Volcanic Islands, Ocean Trenches
12. What is the difference between P
and S waves and Surface waves?
 P-Waves = arrive at the surface first, move by compressing
and expanding the ground like a slinky
 S-Waves = arrive at the surface second, move side to side,
slower than P-Waves
 Surface Waves = these waves move slower than P-Waves and
S-Waves.
13. List some ways that mountains
can form?
 Convergent continental plates form mountains.
 Convergent continental and oceanic plates form volcanic
mountains.
 Hot spots form volcanic island mountains
14. What type of rock makes up most
of the ocean floor?
 Basalt which is a fine-grained rock.
Basalt
15. How is volcanic ash formed?
 Volcanic ash is formed from exploding pumice.
16. Why do volcanoes form where
plates collide?
 Magma forms from the oceanic crust melting through the
process of subduction. The magma rises because it is less
dense than the surrounding rock and its lava forms a volcano
when it reaches the surface.
17. Name the three types of
volcanoes and how each forms.
 Shield = very runny lava, shortest but widest
 Composite = tall and pointy, very viscous lava, alternating
eruptions of cinder or ash and lava
 Cinder Cone = consist primarily of loose cinder around a
single vent
18. How does a caldera form?
 An explosive eruption that causes a collapse of surface rock
into an empty magma chamber
19. How will the viscosity of lava affect
the shape of the active volcano ?
 Thick lava = tall pointed volcanoes
 Thin lava = wide, short volcanoes
20. What evidence do we have to suggest
that the continents were once connected
? What is the name of the theory that
states that the plates are in constant
movement?
 Strings of mountains and fossils across continents that are no
longer connected.
 The continents fit together like pieces to a puzzle.
 Plate tectonics is the theory that stated that all of the plates
are in constant motion
 Pangea is the name of the supercontinent that existed million
of years ago.
21. Describe how you determine
whether an object is in motion or not.
 If the object changes position relative to a reference point.
http://www.planetseed.com/files/flash/science/lab/airspace
/doppler/en/doppler_exp.htm?width=750&height=460&pop
up=true
22. Explain why reference points that
are stationary are usually chosen to
determine whether an object is in
motion.
 If the reference point is moving it’s hard to tell if the object is
in motion.
http://www.planetseed.com/files/flash/science/lab/airspace
/doppler/en/doppler_exp.htm?width=750&height=460&pop
up=true
23. How do you calculate an object’s
speed?
 Total Distance/Total Time
24. Describe what velocity is.
 Speed in a given direction.
25. Demonstrate how to graph
motion. Write a basic problem, solve
the problem and then graph it.
 Use a line graph in which you plot time versus distance, the
Distance
steepness of a line on a graph is called its slope.
Slope=rise/run
Time

26. Describe the motion of an object
as it accelerates.
 A change in the speed or direction of an object
27. Demonstrate how to graph
acceleration. Write a problem, then
solve and then graph it.
 Acceleration = Final Speed-Initial Speed/Time
 To graph you can use both a speed-versus-time-graph and a
distance-versus-time graph
28. Describe what a force is.
 A push or a pull on an object.
29. Describe how balanced and unbalanced
forces are related to an object’s motion.
 Balanced forces will not cause a change in motion of a
moving object.
 Unbalanced forces cause an object to move in the direction
the larger force is moving.
30. Describe friction and identify factors
that determine the friction between two
objects.
 A force that opposes motion through two surfaces that are in
contact
 The force pushing the surfaces together and the roughness of
the surface
31. Identify the factors that affect the
gravitational force between two objects.
 The two factors are mass and distance
 The more mass = more force between it
 Gravitational force depends on the distance between the object’s centers
 As the distance increases, the gravitational force decreases.
32. State Newton’s Three Laws of
Motion and give an example of each
 1st law: An object at rest will remain at rest unless acted
upon by a nonzero force. An object moving at a constant
velocity will continue to move at a constant velocity unless
acted upon by a nonzero net force.
 Ex. A ball will not move unless a force is put upon it.
32. State Newton’s Three Laws of
Motion and give an example of each.
 2nd law: An objects acceleration depends on its mass and the net
force acting on it.
 Acceleration = net force/mass
 Ex: a cart goes faster when something falls out
32. State Newton’s Three Laws of
Motion and give an example of each.
 3rd law: If one objects exerts force on another object, then the second object
exerts a force of equal strength in the opposite direction of the first object. For
every action there is an equal but opposite reaction
 Ex. A swimmer moves because the water pushes her forward when she pushes
back on it
33. Explain how momentum is
determined and conserved.
 Momentum = Mass x Velocity
 Law of conservation of momentum states the in the absence of
outside forces like friction, the total momentum of objects that
interact does not change
 Ex. The amount of momentum two cars have is the same before
and after they interact
34. Describe the motion of an
object during free fall.
 Free fall is the constantly accelerating motion that occurs
when the only force acting on an object is gravity.
35. What factors keep objects in
orbit around the Earth?
 Objects stay in orbit because gravity supplies centripetal
force.
36. What is work and how can it
be determined?
 Work is done on an object when the object moves in the
same direction in which the force is exerted.

Work = Force x Distance
NOT WORK
WORK
37. Define power
 Power equals the amount of work done on an object in a unit
of time

Power = Force x Distance/Time
38. How do machines make work
easier?
 A machine makes work easier by changing at least one of
three factors:

1. The amount of force you exert

2. The distance over which you exert your force

3. The direction in which you exert your force
Changing Force
Changing Distance
Changing Direction
39. How can we calculate the mechanical
advantage and efficiency of a machine?
 Mechanical advantage is the number of times a machine
increases a force exerted on it.
 Mechanical advantage = Output force/input force
 Efficiency of a machine compares output work to input work
 Efficiency = Output work/Input work x 100%
40. Describe how we can calculate the mechanical
advantages of inclined planes, wedges and screws. List
the formula used to calculate each.
 Inclined Plane = length of the incline/height
 The ramp with the smallest mechanical advantage is the steepest
 Wedges = length of the wedge/width of the wedge
 The longer and thinner a wedge is, the greater the mechanical
advantage
 Screws = length around threads/length of screw
 The closer together the threads of a screw are,
the greater the mechanical advantage
41. Classify and describe the mechanical advantage of
each class of lever. List the formula used to calculate
each.
 First Class: mechanical advantage can be less or greater than 1
depending on the fulcrum
 Second Class: mechanical advantage is always greater than 1
 Third Class: mechanical advantage is always less than 1
 Formula: distance from fulcrum to input force/distance from
fulcrum to output force
42. Describe the mechanical advantages of pulleys and
wheel and axles. What formula would you use to calculate
each?
 Pulleys:
 Fixed Pulley: changers the direction of force but not the




amount applied (MA = 1)
Moveable Pulley: changes the direction of the force
(MA = 2)
Block and Tackle: pulley system made up of fixed and
movable pulleys (MA = 3)
MA = the number of pulleys
42. Describe the mechanical advantages of pulleys and
wheel and axles. What formula would you use to calculate
each?
 Wheel and Axle:
The greater the ratio of the wheel radius to the axle
radius, the greater the advantage

Formula = Radius of wheel/Radius of axle

43. Describe the mechanical advantages of compound
machines and how do we calculate the advantage for
them?
 The mechanical advantage of each simple machine is not
affected by the other machines, but their mechanical
advantages combine to produce the mechanical advantage of
the whole machine

Formula: multiply the mechanical advantages of the
simple machines that make up the compound machine
44. Explain how energy, work, and power
are related. Use a Venn diagram.
45. Name and describe the two
basic types of energy.
 Kinetic Energy: the energy that an object has due to its
motion
 Potential Energy: the energy an object has because of its
position or shape
46. What are the six forms of
energy? Give an example of each.
 Mechanical energy: ex. Falling basketball and moving car
 Nuclear energy: ex.nuclear power plant
 Thermal energy: ex. A heated pot of water at 75 degrees has
more thermal energy than the same water at 30 degrees
 Electrical energy: ex. lightning
 Electromagnetic energy: ex. microwaves and x-rays
 Chemical energy: ex. bonds are broken in your cells &
release energy for your body to use
47. What does the law of
conservation of energy state?
 When one form of energy is transformed to another, no
energy is lost in the process. Energy cannot be created or
destroyed.
48. Explain how static electricity
builds up and transfers.
 Static electricity is an imbalance between negative and
positive charges in objects. Static electricity transfers
when the rubbing of certain materials against one another
can transfer negative charges, or electrons.
 Static discharge is the loss of static electricity as electric
charges transfer from one object to another.
49. What are the differences between from
conductors and insulators? List two of each.
 Conductors allow electrons to flow easily
 example: most metals
 Insulators do not allow electrons to flow easily
 ex. air and wool and rubber
50. Using a diagram, describe the basic features
of an electric series and parallel circuit.
Wire
Wire
51. What causes charges to move
through a circuit?
 Voltage or difference in electric potential energy
52. Explain Ohm’s Law. What is
the formula to calculate
resistance?
 Ohm’s Law describes how voltage, current, and resistance
are related.
 Voltage = Resistance x Current
 The unit is Ohms Ω
53. How do you calculate electric
power and energy use?
 Power (Watts) = Voltage (V) x Current (A)
 Current (A) = Power (Watts) /Voltage (V)
 Energy (kWh) = Power (kW) x Time (hours)
54. Identify each property of a
magnet.
 magnets attract iron and materials that contain iron, nickel
and cobalt.
 magnets attract opposite poles and repel the same poles of
other magnets
 magnets, when freely swinging, one end always points north
55. Explain how magnetic poles
interact.
 Each magnet has two ends, each called a magnetic pole.
Magnetic poles that are unlike attract each other, and
magnetic poles that are alike repel each other.
56. What is a magnetic field?
 The area of magnetic force around a magnet. The magnetic
field lines spread out from one pole, curve around the
magnet, and return to the other pole.
57. Describe the characteristics of
solenoids and electromagnets
 Solenoids: a coil of wire with a current, the two ends act like
the poles of a magnet
 Electromagnets: are solenoids with a ferromagnetic core, the
overall magnetic field of an electromagnet is much stronger
than that of a solenoid. Turning the current off and on turns
the electromagnet off and on.
Solenoid
Electromagne
t
58. Explain how mechanical
energy can be converted to
electrical energy in a generator.
 A generator uses motion in a magnetic field to produce
current. The slip rings turn with the armature and transfers
current to the brushes. The crank rotates the armature. The
motion of the armature in the magnetic field induces a
current and when the brushes are connected to a circuit, the
generator can be used as an energy source.
59. Explain the difference
between an alternating and direct
current.
 Alternating Current: a constantly reversing current
Ex. Electricity through a wall outlet
 Direct Current: a current with charges that flow in one
direction
Ex. Battery
60. Explain how the Doppler Effect
relates to pitch.
 The change in sound waves changes the frequency and is
heard as a change in pitch.
 Sound waves in front of a moving object are shortened and
have a higher frequency and higher pitch
 Sound waves trailing behind a moving object are lengthened
have a lower frequency and lower pitch.
61. What property of sound waves
affects the pitch of a sound? What
property of sound waves affects
the loudness of a sound?
 Loudness – determined by amplitude of a wave
High amplitude = loud
Low amplitude = high
 Frequency – determines pitch
High frequency = high pitch Low frequency = low pitch
62. Describe how sound intensity
changes with the distance. Give an
example.
 Intensity decreases as the distance increases
Ex. Standing behind a fire truck’s siren
 Intensity increases as the distance decreases
Ex. Standing in front of a fire truck’s siren
63. How is music different from
noise?
 Music is a set of notes that combine in patterns that are
pleasing. The vibrating chords set air particles into vibration.
 Noise is unwanted sound. Some examples are a running
engine, operating a machine, and loud tools.
64. List and describe two different
ways that animals and people use
sound waves.
 Animals (bats and dolphins) use echolocation to navigate
and find food, bats use ultrasound which are sound waves
with frequencies above the human range of hearing.
 People use sonar and ultrasound imaging to observe things
they cannot see directly. People use sonar to detect and
locate objects under water, depth of water and to map the
ocean floor and sonograms.
65. List and describe two ways in
which a surface can reflect light.
 regular reflection (aka specular reflection) – parallel rays of
light hit a smooth surface, the image is a copy of the object
formed by reflection or refracted rays of light
 diffuse reflection – parallel rays of light hit an uneven surface,
an unclear image is seen, most objects reflect light diffusely.
66. What is the difference
between primary and secondary
colors of light?
 Primary are three colors that combine to make any other
color (red,green,blue)
 Secondary is when the three primary colors of light are
combined in equal amounts.
67. Compare plane, concave and
convex mirrors in terms of the type
of surface they have and the type
of image that they produce.
 Plane mirror has a flat surface, the image is upright and the
same size as the object.
 Concave mirror has a surface curved inward, it produces a
real or virtual image, depends on the distance.
 Convex has a surface that curves outward, it always produces
a virtual image that is smaller than the object.
Plane mirror
Concave
mirror
Convex
mirror
68. Explain how refraction of light
occurs. Give an example of
refraction.
 When light rays enter a medium at an angle, the change in
speed causes the rays to bend. Ex. A rainbow
69. Use the terms retina, rods,
cones and optic nerve to explain
how an image is formed and
interpreted by the human eye.
 Light enters through lens and a real image is projected onto
retina
 Retina: layer of cells that line the inside of the eyeball
 Rods: cells in the retina that respond to small amounts of
light
 Optic Nerve: carries signals from the eyes to the brain
70. When comparing your body to
a simple machine, most of the
bodies bones and muscles work to
act together as what type of
machine?
 Levers