# 8th grade physical science sol review key

```Physical Science Review
I. Scientific Method
The independent variable is the variable that the experimenter changes on purpose.
The dependent variable "depends" on which independent variable is used. It is what is being measured or observed.
The control is one of the independent variables. It is the one that all the others are being compared to. It is often the condition with nothing added or the normal way it is done.
A. Problem: Does too much water affect plant growth?
Independent Variable: Amount of Water
Dependent Variable: Plant Growth
Control: Plant with normal amount of water
B. Problem: Will the temperature of water affect how much goldfish will eat?
Independent Variable: Temperature of water
Dependent Variable: Amount of food goldfish will eat
Control: Regular temperature of water for goldfish
C: Problem: Are mosquitoes attracted to perfume?
Independent Variable: Perfume
Dependent Variable: Mosquito attraction
Control: Not wearing any perfume
D. Hypothesis: If water is heated, then more salt will dissolve.
Independent Variable: Temperature of Water
Dependent Variable: Amount of salt dissolved
Control: Room temp water
II. Metric System
kilo = 1000
centi = 0.01
milli = 0.001
Which measurement would you use to measure the following?
A. the length of a piece of paper
centimeters
B. the volume of a soda bottle
liters
kilograms
E. the volume of a glass of water milliliters
F the volume of a fish tank full of water liters
G. the mass of a grain of rice
milligrams
H. the length of a grain of rice
millimeters
I. the distance from school to the mall kilometer
J. the mass of a penny
grams/centigrams
K. the length of the science room meters
L. the length of a pencil
centimeters
III. SI units of measurement
m/s s
m
g/cm3
Newton Watt
Joule
m/s2
g/mL
What is the SI unit of measurement for the following?
A. force
B. acceleration
C. speed
D. length
E. temperature
F. Energy
G. Work
H. Power
I. Mass
J. Time
K. Density
Newton
m/s2
m/s
m
Kelvin
Joule
Joule
Watt
kg
sec
g/ml or g/cm3
kg Kelvin
IV. Graphing
A. Identify the types of graphs illustrated below. a._Histogram_
b._Line plot___
c._Scatterplot__
B. Answer the following questions utilizing the graphs above.
1. In graph A, how many students are in the 56­59 inch range? _12_
2. How many students are in the 48­51 inch range in graph A? _2__
3. What does graph B illustrate? _____Homework Grades____
4. How many students have an “A” in graph B? _____3______
5. How many students have a “D” in graph B? _____4_______
6. What grade do most of the students in the class have in graph B? ____"C"_____
7. What is the label on the x­axis (the IV) for graph C? __Reading__
8. What is the label on the y­axis (the DV) for graph C? _Mathematics_
9. What type of relationship does graph C represent? _Positive__
10. What is the name of the straight line on graph C? _Line of best fit__
V. States of Matter
A. Identify the states of matter in the illustration below. Then write a description about each state of matter below its picture.
SOLID:
Tightly packed,
definite volume & shape,
low energy GAS:
LIQUID:
Flowing particles,
No shape OR Volume but no shape
volume,
medium energy high energy PLASMA:
+/­ particles,
No shape OR volume,
collide violently B. Identify the phase change for each of the arrows in the diagram below. Then write a simple definition for each phase change and state if it is endothermic (heat in) or exothermic (heat out).
1. Melting = solid to liquid, endothermic
2. Vaporizing = liquid to gas, endothermic
3. Condensing = gas to liquid, exothermic
4. Freezing = liquid to solid, exothermic
VI. Properties & Changes
Characteristics of properties are determined by the use of the senses and the involvement of matter in chemical reactions. Characteristics of changes are determined by a change in the appearance of the substance or the creation of a new substance with new properties.
A. Write a brief definition for each of the words below:
a. Physical Property: Describes the appearance or characteristics of a substance.
b. Chemical Property: Describes how it can react in a chemical reaction.
c. Physical Change: Change in appearance of a substance.
d. Chemical Change: Creation of a new substance with new properties.
B.
Determine if the following properties are physical or chemical.
1. Color ­ P 2. Burning ­ C 3. Weight ­ P
4. Hardness ­ P
5. Reactions with acid ­ C 6. Boiling point ­ P 7. Density ­ P 8. Rusting ­ C
C. Determine if the following changes are physical or chemical.
1. Sharpening a pencil P
4. Mixing sand and water P
7. Spray painting a car P
2. Evaporating Water P 3. Rusting steel wool C
5. Burning a pencil C 6. Freezing water P
8. Melting ice cream P 9. Mixing acid and sugar C
VII. Density
mass / volume
Density is a physical property of an object. It is how tightly packed a substance's compound are. It is calculated by taking the mass of a substance divided by its volume, in g/cm3 or g/mL. It does not depend on how much of the object there is because it is expressed as the amount of mass in one cm3 or mass in one mL.
An object will float on a liquid if its density if less than the density of the liquid. A liquid will float on top of another liquid if it doesn't mix with the other liquid and its density is less than the density of the other liquid.
A. A gold brick has the dimensions of 10 cm x 3 cm x 2 cm. If the mass of this gold brick is 1158 g, what is the density of gold? 19.3 g/cm3
B. A liquid has a volume of 30 mL and a mass of 15 g. What is the density? 0.5 g/ml
C. Layer the three liquids and the three solids in the diagram below.
B
2
C
3
A
1
VIII. Classification of Matter
Determine whether the following are elements, compounds, homogeneous mixtures, or heterogeneous mixtures.
A. hot chocolate homo mix
F. Lucky Charms cereal hetero mix
B. oxygen
element
G. carbon dioxide
Compound
C. air in a room homo mix
H. water
Compound
D. Italian salad dressing hetero mix
I. N2
Element
E. sugar water homo mix
J. NaCl
Compound
IX. Acids and Bases
Acids release H+ ions when dissolved in water and have pH values of less than 7.
Bases release OH­ ions when dissolved in water and have pH values of greater than 7.
1. State whether the following are acids or bases.
A. HCl ­ Acid
D. H2CO3 ­ Acid
B. NaOH ­ Base
E. KOH ­ Base
C. Al(OH)3 ­ Base
2. Different substances have pH values of 3, 5, 7, 9, and 11.
A. Which is neither an acid nor a base? 7
B. Which is the strongest acid? 3
C. Which is the weakest acid? 5
D. Which is the strongest base? 11
E. Which is the weakest base? 9
X. Organic vs. Inorganic Compounds
Organic compounds contain the element carbon (C). Inorganic compounds do not contain carbon. For each of the compounds below, state if they are organic or inorganic.
1. CO2 Organic 2. NaCl Inorg
5. C6H12O6 Org 6. NO2 Inorg
3. H2O Inorg
7. H2CO3 Org
4. CH4 Organic
8. NaOH Inorg
XI. Periodic Table Review
Atomic # = # protons
# protons = # electrons
# neutrons = Atomic mass ­ Atomic #
Group # = # valence electrons (except for groups 13 ­ 18. Take the group # and subtract 10 to get the number of valence electrons)
**Remember valence electrons are the electrons found in the outer energy level.
3
6.94
3
3.94 = 4
3 1
2
1
13
26.98
13
13.94 = 14
13
13
3
3
5
10
10.81
20.18
5
10
10.18 = 10 5.81 = 6
5
10
13
18
2
2
7
3
Metal
Metal
Nonmetal Metalloid Metal
12
24.31
12
12.31 = 12
12
2
3
2
9
19
9
10
9
17
2
7
Nonmetal
XII. Chemical Formulas
Subscripts = number of atoms of the element before it.
*Remember if there is no subscript then there in only one of that type of atom!
H2SO4 H = 2
S = 1
O = 4
A.
B.
C.
D.
E.
Fe2O3 Fe = 2 O = 3
CaSO4 Ca = 1 S = 1 O = 4
H2O H = 2 O = 2
H2SO4 H = 2 S = 1 O = 4
C6H12O6 C = 6 H = 12 O = 6
XIII. Binary Compounds
In binary compounds, ions combine to form a neutral compound.
Na1+ + S2­ Na2S
Mg2+ + S2­ Mg2S2 (or MgS if you use lowest ratio)
Use the following symbols and oxidation numbers to determine the binary compound formed.
A.
B.
C.
D.
Ba2+ + F1­ = BaF2
Al3+ + Br1­ = AlBr3
Ni3+ + O2­ = Ni2O3
Fe3+ + O2­ = Fe2O3
XIV. Ionic vs. Covalent Bonding
An ionic bond is when a metal bonds with a nonmetal. Electrons are •
lost and gained in an ionic bond.
A covalent bond is when a nonmetal bonds with another nonmetal. •
Electrons are shared in a covalent bond.
Determine if the following compounds are ionic or covalent.
1. CaCl2 I 2. CO2 C 3. H2O C 4. K2O I
5. NaF I
6. CH4 C 7. SO3 C 8. LiBr I
9. MgO I
10. HCl C
XV. Balanced Equations
The Law of Conservation of Mass (Matter) states that mass cannot be _created__ or __destroyed__.
Equations are balanced when there are the same number of atoms of an element on the reactant side of the equation as there are of that element on the product side.
Which of the following equations are balanced? Underline the reactants and circle the products.
A. N2 + 2H2 2NH3
NO
B. PbO2 PbO + O2
NO
C. BaCl2 + Al2O3 BaO + 2AlCl3
NO
D. Pb(NO3)2 + 2NaI PbI2 + 2NaNO3
E. FeO4 + 4H2 Fe + 4H2O
YES
YES
XVI. Nuclear Energy ­ Fission vs. Fusion
Identify the pictures below as fission or fusion. Then below each picture write a brief description of the reaction.
ENERGY
Fission
­Dividing of a large atom to smaller atoms
­Nuclear reactors & weapons
ENERGY
Fusion
­Combining of small atoms into large atom
­Takes place on sun & stars
­Products are safe (Helium)
XVII. Energy
A. Law of Conservation of Energy states that energy cannot be _created_ or _destroyed_, it can only change __forms__.
B. There are two types of energy:
a. Potential energy: Stored energy or energy of position
b. Kinetic energy: Energy of motion
c. Identify each example below as potential or kinetic energy.
1. Rolling rock KE
PE
2. Sitting dog
3. Top of a waterfall PE
4. Bottom of a roller coaster KE
PE
5. Top of a pendulum
6. Bottom of a pendulum KE
C. Potential and kinetic energy can be broken down into six forms of energy. Give a definition for each form of energy below.
a. Heat energy: increase in temp
b. Light energy: makes things visible
c. Electrical energy: flow of electrons
d. Mechanical energy: makes things move
e. Nuclear energy: changing nucleus of atom, fission or fusion
f. Chemical energy: stored and then released in a chemical reaction
g. Identify what form of energy is present in each example below.
1. food Chemical
2. fire Thermal/Light
3. lamp Light/thermal
4. windmill Mechanical
5. chain reaction Nuclear
6. parallel circuit Electrical
7. power in house Electrical
8. swinging Mechanical
9. the sun Nuclear
10. flashlight Light/thermal
11. battery Chemical
12. hot water Thermal
D. Heat energy can be transferred in three ways. Label each picture and briefly describe how the heat energy is transferred.
Convection
­transfer of heat
by waves (bulk movement)
­liquids & gases
Conduction
­transfer of heat
by direct contact
­transfer of heat by
electromagnetic waves
XVIII. Phase Change Graph
Look at the phase change graph to answer the following questions.
1. What is the state of matter from A to B? ___Solid___
2. What is the state of matter from C to D? __Liquid_____
3. What is the state of matter at F? _____Gas______________
4. What is the change in state from B to C? ___melting____
5. What is the change in state from D to E? __vaporizing_
6. Where is the heat of fusion? ______B to C_____________
7. Where is the heat of vaporization? ______D to E_________
8. As time increases, what is being added to the substance? ____Heat_______
9. Does the temperature increase as melting is occurring? _____NO!!!!______
10. Does the temperature increase as the substance is in the liquid phase? __YES__
XIX. Waves ­ Light vs. Sound Waves
A. Label the parts of both waves and identify the name of each wave using the following words. Some words may be used more than once.
Crest
Wavelength
Rest Position
Transverse Wave
(normal line)
Amplitude
Trough
Longitudinal Wave
(compressional wave)
Wavelength
Compression
Rarefaction
B. Sound Waves
Use the word bank below to fill in the reading passage.
Energy
All waves carry ___________. Sound waves are called Longitudinal
Medium
___________________ waves. They require a ____________ in order (compressional)
Faster
to travel. They travel _______________ in warmer temperatures than in Travel
cold temperatures. The waves can ______________ through all states Solids
of matter but travel faster through _________________. This is Molecules
Close
because in solids the _______________ are very ___________ Frequency
together and influence each other. As the ________________ of the Wavelength
wave increases, the _______________ decreases.
*Identify the phenomenon illustrated in the picture below and describe what is happening.
Doppler Effect
­change in sound due to motion
Car A hears sound loudest, Car B hears sound softest
C. Light Waves
Light waves do not require a medium in order to travel. There •
are many different types of light waves as illustrated in the electromagnetic spectrum.
Light waves travel faster than sound waves, which is why we •
see lightening before we hear thunder.
1. Which wave has the highest frequency? __Gamma Rays___
2. Which wave has the lowest frequency? __Radio Waves____
3. What is the only light we can see? ____Visible Light______
4. What colors is visible light broken into when they refract? ______________ROY G B(I)V____________________
5. What happens when you see a green shirt? __________________ _______Green is reflected, all others are absorbed__________
D. Reflection vs. Refraction
Identify each picture below as reflection or refraction. Then write a brief summary on each.
Refraction:
Bending of waves caused by a change in speed (different mediums)
Reflection:
A wave strikes an object
and bounces back.
A = line of incidence
B = angle of incidence
C = angle of reflection
D = line of reflection
E. Lenses & Mirrors
Draw an example of a concave lens and a convex lens. Then write a brief description of what each lens does.
Concave Lens­
objects appear smaller
­Nearsightedness
Convex Lens­
Brings light together, objects appear larger
­Farsightedness
Draw an example of a concave mirror and a convex mirror. Then write a brief description of what each mirror does.
Concave Mirror­
Image is large
and upside down
Ex. Makeup mirror
Convex Mirror­
Image is smaller
and shows a wide area
Ex. car mirror, store security mirror
XX. Motion
1. A change in an object’s location is _____motion_____.
2. A push or pull that is exerted on an object is ___force___.
3. _____Velocity___ is the speed of an object and its direction of motion.
4. The rate at which velocity changes is __acceleration____.
B. Look at the date table and answer the following questions.
1. Which mode of transportation is the fastest? ____driving a car____
2. Which mode of transportation is the slowest? ___walking___
3. What is the distance traveled in all three trials? (HINT: D = S x T) ___600 km____
Look at the graphs below and answer the following questions.
1.
2.
Which car traveled the fastest? __Car #1____
Which car traveled the slowest? ___Car #4_____
3. What is the average speed? (Average speed = total distance / total time) _______2 m/s__________
4. Is the speed of the object constant or not constant? Why? _____Yes ­ it is a straight diagonal line ­ all speeds along the line are the same____
C. Mass vs. Weight
Mass is the amount of matter in an object. It is measured in grams •
using a balance.
Weight is a measure of the force of gravity on an object. It is •
measured in Newtons using a scale.
You weight will change if you travel to the moon because there is a •
change in gravity. However, your mass will remain the same.
The force of gravity is determined by two things:
•
o __the mass of the object________
o __the distance between the objects__________
Look at the pictures below and state which position/object will have •
the greatest gravitational pull on it.
More Mass
Closest to center of earth
D. Newton’s Laws of Motion
I. Identify each picture below as one of Newton’s laws. Then briefly describe each law next to the picture.
1st Law
Motion, Motion
Rest, Rest
3rd Law
Action/Reaction
2nd Law
F = ma
II. Predict the motion. Read each sentence and predict what will happen according to Newton’s Laws of Motion.
1. Newton’s Second Law: You hit a ping­pong ball and a tennis ball with a tennis racket. Which one will travel farther? __w/out air resistance = ping pong ball, with air resistance = tennis ball_____
2. Newton’s First Law: If you leave a cookie on a plate and there is no one else in the house, where will the cookie be in an hour? ____still on the plate______
3. Newton’s Third Law: If you let the air out of a balloon, what will happen to the balloon? ____it will fly in the opposite direction________
4. Newton’s First Law: The horse you are riding on stops quickly. What happens to you? __you continue to fly forward____________
E. Friction
•
•
Friction is a __force____ that ___opposes___ motion.
Draw the friction arrows in the pictures on the right.
f
f
F. Simple Machines
List the six simple machines: Screw, Wedge, Lever, Pulley, Wheel •
& Axle, Inclined Plane
Label all of the simple machines you see in the wheelbarrow picture.
•
Wedge
Lever
Wheel & Axle
inclined plane
G. Using Formulas
Speed = distance/time s = d t
Force = Mass x acceleration
F = ma
Work = force x distance
W = Fd
Power = work/time
P = W
t
A. A train travels a distance of 1,200 kilometers in 20 hours. What is the speed? 60 km/hr
B. It takes a caterpillar 15 minutes to crawl 3 meters up a tree. How fast was it crawling? 0.2 m/min
C. What force gives a 6 kg object an acceleration of 4 m/s2? 24 N
D. What force gives a 60 kg object an acceleration of 2.2 m/s2? 132 N
E. How much work is done when you hold a 50 N box 1.2 meters above the floor? 60 J
F. How much work is done when you use 300 N of force to move a box 3 meters? 900 J
G. How much power is needed to move a 600 N box 4 meters in 2 seconds? 1200 W
XXI. Magnetism & Electricity
A.
a.
Static electricity: Buildup of charges on an object.
Correctly label the charges in the balloon illustration to the right.
­
­
­
­
+
+
+
+
B. Current electricity ­ Series vs. Parallel circuits
a. Draw an example of each type of circuit. Be sure to create a key for all of the parts of the circuits.
•
1. When you add lights to a series circuit, what happens? ___lights get dimmer___
2. When you add lights to a parallel circuit, what happens? ____lights stay the same____
3. What happens in a series circuit when one light goes out? ___all other lights go out_____
4. What happens in a parallel circuit when on light goes out? __all other lights stay on__
•
Complete the circuit in the illustration.
C. Conductors and Insulators
•
•
•
Conductors allow for the easy flow of electrons.
Insulators slow down or stop the flow of electrons.
Identify each picture below as a conductor or an insulator.
I
C
I
C
I
C
D. Magnetism
•
Draw the field lines for each of the magnet pairs.
What is an electromagnet? A temporary magnet produced by a •
wire coil around an iron core.
•
o
o
o
o
List four ways to increase the strength of an electromagnet.
Tighten the coils
Increase the current
Use an iron core
­Increase number of nails
­Increase voltage
8th Grade Review Questions ­ Part 1
1. Which of the following could best be used to demonstrate energy being transformed from electricity to heat?
A. A magnifying glass
B. A triple beam balance
C. A toaster
D. A gas oven
2. Insulation materials reduce heat loss because they ­
A. Are poor conductors
B. Block out the sun
C. Reduce evaporation
D. Promote convection
3. Which process is a physical change?
A. Rusting iron
B. Burning coal
C. Tarnishing silver
D. Melting ice
4. Water stored behind a dam is an example of what type of energy?
A. Kinetic
B. Potential
C. Solar
D. Chemical
5. A burning candle is in the process of transforming ­
A. Heat energy into chemical energy
B. Chemical energy into light and heat
C. Chemical energy into mechanical energy
D. Chemical energy into nuclear energy
6. In the diagram, what essential part of an electric circuit is missing at position X?
B. On/off switch
C. Wires
D. Source of electric current
7. In the chemical formula for ammonia, NH3, what does the subscript 3 represent?
A. The number of nitrogen and hydrogen atoms in each molecule of ammonia
B. The number of hydrogen atoms in each molecule of ammonia
C. The number of ammonia atoms that will bond together
D. The number of nitrogen atoms in each molecule of ammonia
8th Grade Review Questions ­ Part 2
1. When a base is mixed with an acidic solution, neutralization occurs because the ­
A. Base reaches absolute zero
B. Acid evaporates
C. Base chemically reacts with the acid
D. Mass of the solution increases
2. What type of energy does the windmill use to do work?
A. Mechanical
B. Nuclear
C. Chemical
D. Electrical
3. Because zinc can combine with other substances but cannot be changed into a simpler substance by ordinary chemical process, zinc is classified as ­
A. A compound
B. A mixture
C. An element
D. An acid
4. Which of the following is a true statement about the magnetic field between two magnets?
A. The south pole of one magnet is attracted to the south pole of the other magnet
B. The south pole of one magnet is attracted to the north pole of the other magnet
C. The north pole of one magnet is attracted to the north pole of the other magnet
D. The south pole of one magnet is attracted to both poles of the other magnet
5. An electric light bulb is hot to the touch because ­
A. Current passing through it produces heat
B. Its magnetic field produces a large amount of heat
C. Evaporation causes an object to heat up
D. Its chemical reactions produce heat
6. Which instrument would most accurately and precisely determine the mass of a toy car?
A. An electronic light meter
B. A spring scale
C. A triple­beam balance
7. The diagram shows a block from the periodic table. The number six represents the­
A. Atomic mass of the element carbon
B. Atomic number of the element carbon
C. Number of neutrons in the element carbon
D. Number of valence electrons in the element carbon
8th Grade Review Questions ­ Part 3
1. A mixture of iron filings and sulfur can easily be separated by ­
A. Placing the mixture in water
B. Performing a chemical reaction
C. Heating the mixture
D. Using a magnet
2. Of the states of matter, gas is the only state that ­
A. Is fluid
B. Has mass
C. Is highly compressible
D. Has a definite shape
3. According to the data in the table, which sample of matter is most likely a metal?
A. 1
B. 2
C. 3
D. 4
4. Expansion joints such as test are put on bridges because the concrete expands and contracts. This happens when ­
A. Chemicals get on the concrete
B. The temperature changes
C. The amount of light changes
D. The concrete gets wet
5. How far offshore is the deepest point of the ocean on this graph?
A. 0 m
B. 5000 m
C. 160 km
D. 240 km
6. Each student in a science class of 25 conducts the same experiment. One student gathers all the data from her classmates and summarizes the results of the experiment for the class. She compares the data she personally recorded with the class data. Which of these might indicate to her that her results are valid?
A. Three other classes performed the same experiment
B. The same experiment was repeated two years in a row
C. Many other students recorded data similar to hers
D. Another student in her class reached a different conclusion
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