Grade 8 Physical Posttest
Select the best answer to each question.
____
1. The diagram below shows how the temperature of an amount of water changed as the water changed states.
Why is the temperature constant as water goes from point 1 to point 2, showing when it changes from ice to
liquid water?
A. Ice releases energy to the surroundings to form attractions between the particles as it
melts.
B. Ice takes in energy from the surroundings to form attractions between the particles as it
melts.
C. Ice takes in energy from the surroundings to break apart attractions between the particles
as it melts.
D. Ice releases energy to the surroundings to break apart attractions between the particles as it
melts.
____
2. Aisha is using a computer model to explore what happens to the particles in water when it changes from a
liquid to a gas. What will the model show about the motion of liquid water and water vapor?
A. The motion of the particles is the same in both states, but they move faster in the gas state.
B. The particles in the liquid do not move, but the particles in a gas can move back-and-forth.
C. The particles in a gas can slide past each other, while the particles in a liquid are locked in
place.
D. The particles in a liquid can slide past each other, while the particles in a gas are free to
move in all directions.
____
3. Jorge is pouring water from a bottle into a glass. In a model, how should the particles of water move to
explain why water flows from a liquid to a glass?
A. They should be sliding past each other at all times.
B. They should not move at all until the water is poured.
C. They should be move very quickly in one place at all times.
D. They should be moving freely in all directions when the water is poured.
____
4. The gravitational force on Mars is about one-third that of Earth’s gravitational force. If a space probe has a
mass of 300 kg and a weight of about 660 pounds on Earth, what would be the mass and approximate weight
of this probe on Mars?
A.
B.
C.
D.
____
mass = 100 kg, weight = about 220 pounds
mass = 300 kg, weight = about 220 pounds
mass = 300 kg, weight = about 660 pounds
mass = 900 kg, weight = about 660 pounds
5. Kale measures a block as shown in the diagram below.
What is Kale measuring?
A. density
B. mass
C. volume
D. weight
____
6. Kanya calculates what her weight would be on every planet in the solar system. She determines her weight on
Jupiter would be more than double her weight on Earth. What does this weight difference indicate about
Jupiter?
A. Objects gain mass when they go to Jupiter.
B. Objects lose mass when they go to Jupiter.
C. The gravitational pull on Jupiter is less than on Earth.
D. The gravitational pull on Jupiter is greater than on Earth.
____
7. The density of a substance equals its mass divided by its volume. Talia listed the density of some common
materials at 20 °C.
Material
gasoline
mercury
milk
water
Density (g/cm3)
0.70
13.6
1.03
0.998
If Talia has 10 grams of each material, which material has the greatest volume?
A.
B.
C.
D.
gasoline
mercury
milk
water
____
8. Luis wants to compare the density of three solid objects that are different shapes and sizes. What information
does he need to make the comparison?
A. how flat or round each object is
B. the relative weights of the objects
C. the mass and volume of each object
D. how opaque or transparent each object is
____
9. Brianna measures the mass of 10 milliliters (mL) each of two liquids. Liquid A has a mass of 11 grams (g).
Liquid B has a mass of 10 g. The equation d = m/V is used to calculate density. What is the difference in the
densities of Liquid A and Liquid B?
A. 0.0 g/mL
B. 0.1 g/mL
C. 1.0 g/mL
D. 11 g/mL
____ 10. Kavish mixes a black liquid and a clear liquid. He knows the two liquids do not mix well. Kavish allows the
mixture to settle for 30 minutes.
Which of these statements is true?
A.
B.
C.
D.
The clear liquid is less dense than the black liquid.
The clear liquid is less soluble than the black liquid.
The clear liquid is less reactive than the black liquid.
The clear liquid is less conductive than the black liquid.
____ 11. Darius is comparing five thin sheets that have the same volume but are made of different materials. One of the
sheets is made of copper. Which of the other sheets has an electrical conductivity most similar to copper?
A. aluminum
B. glass
C. paper
D. wood
____ 12. Henry measures the temperatures at which three liquids change into gases. What property is Henry
comparing?
A. solubility
B. boiling point
C. melting point
D. thermal conductivity
____ 13. What type of substance is always made up of a single type of atom?
A.
B.
C.
D.
mixture
element
molecule
compound
____ 14. Razi observes his surroundings as he takes his little brother to the playground shown below.
Which things at the playground are made up of atoms of elements?
A. everything
B. the air and the rock
C. the trees and the grass
D. the swing set, slide, and seesaw
____ 15. Carbon monoxide detectors help protect people from being poisoned by carbon monoxide gas. A molecule of
carbon monoxide is made up of one carbon atom and one oxygen atom. Which of the following best
describes the properties of carbon monoxide?
A. It has a half the properties of carbon and half the properties of oxygen.
B. It has mostly the properties of oxygen and a few properties of carbon.
C. It has a unique set of properties that are different from carbon and oxygen.
D. It has the same properties as all other gases that are made of carbon and oxygen.
____ 16. A portion of the periodic table is shown below.
What is true of elements within a period?
A.
B.
C.
D.
Their atomic numbers increase by 1 from left to right.
Their atomic numbers increase by 1 from top to bottom.
Their average atomic masses increase by 1 from left to right.
Their average atomic masses increase by 1 from top to bottom,
____ 17. Lithium (Li), magnesium (Mg), and barium (Ba) are found in the first two rows of the periodic table. Why are
these elements grouped on the left side of the periodic table?
A. They are unreactive gases.
B. They are reactive metals.
C. They are reactive nonmetals.
D. They are unreactive metalloids.
____ 18. Helium is an unreactive gas with an atomic number of 2 and atomic mass of 4. Krypton (Kr) is found three
rows below helium in the same column of the periodic table. Why is kyrpton grouped below helium in the
periodic table?
A. It is dense solid.
B. It is an unreactive gas.
C. It has a smaller atomic mass.
D. It has a smaller atomic number.
____ 19. Calcium is an element. What is the smallest particle of calcium that has the same chemical properties of
calcium?
A.
B.
C.
D.
an atom of calcium
a proton from a calcium atom
an electron from a calcium atom
a molecule that contains calcium
____ 20. The characteristics of atoms, such as the atomic number, depend on the subatomic particles that make up the
atom. What determines the atomic number of an element?
A. the number of protons
B. the mass of the neutrons
C. the number of electrons
D. the mass of the nucleus
____ 21. Even though atoms are much too small to see, experiments have helped scientists learn about the subatomic
particles that compose atoms. Which part of the atom takes up most of the space in an atom?
A. the nucleus
B. the neutron
C. the electron cloud
D. the proton cluster
____ 22. Some compounds are classified as acids or bases. The pH scale shows how acidic or how basic these
compounds are. The lower the pH, the more acidic a compound is. The higher the pH, the more basic it is.
Sodium hydroxide, a compound commonly found in drain cleaners, has a pH of 13.
Which of these phrases describes sodium hydroxide?
A.
B.
C.
D.
highly basic
highly acidic
slightly basic
slightly acidic
____ 23. The label on a chemical in a science laboratory reads, “Strong Acid.” Based on this label, what can a student
best determine about the chemical?
A.
B.
C.
D.
It has a low pH.
It is a clear liquid.
It has a high density.
It has a low melting point.
____ 24. Strong acids and strong bases are both corrosive and must be handled with care. Which of the following is the
chemical formula of a strong base?
A.
B.
C.
D.
HNO 3
NaOH
H 2 SO 4
CH 3 COOH
____ 25. You are shining a light through liquids A and B, which are both mixtures. You can see the light pass through
A, but B looks cloudy and you see tiny particles floating in it.
Which of these statements best describes the liquids?
A.
B.
C.
D.
Both the liquids are suspensions.
Both the liquids are solutions.
A is a suspension, and B is a solution.
A is a solution, and B is a suspension.
____ 26. Raymond uses different methods to separate mixtures. Which mixture could be separated using a magnet?
A.
B.
C.
D.
mixture of salt and pepper
mixture of sand and water
mixture of sand and pebbles
mixture of iron filings and salt
____ 27. A sealed flask contains ammonia gas (NH 3 ). It is classified as a pure substance. A second sealed flask
contains a mixture of nitrogen gas (N 2 ) and hydrogen gas (H 2 ). Which statement best explains why the flask
of nitrogen gas and hydrogen gas would NOT be classified as a pure substance?
A.
B.
C.
D.
The flask contains more than one type of element.
Each substance can be decomposed into a simpler substance.
The elements nitrogen and hydrogen are not chemically combined.
The contents of the flask cannot be separated by chemical means.
____ 28. Trini adds 10 g of baking soda to 100 g of vinegar. The mixture begins to bubble. When the bubbling stops,
Trini finds the mass of the resulting mixture. She determines its mass is 105 g. Why has the mass changed?
A. A gas has formed and left the mixture.
B. Vinegar evaporated during the experiment.
C. Mixtures always are less massive than their parts.
D. Mass was destroyed when vinegar reacted with baking soda.
____ 29. Annika does an experiment using three glass beakers.
The beaker with the water has 56 g of mass. The beaker with the sugar solution has 67 grams of mass. What is
the mass of the sugar in the first beaker?
A. 11 grams
B. 17 grams
C. 56 grams
D. 123 grams
____ 30. Stefano takes a piece of ice with a mass of 100 g and places it on a metal sheet. The ice melts and then
evaporates. What has happened to the 100 gram mass?
A.
B.
C.
D.
The ice now exists as a 100 g mass of water vapor.
The ice has evaporated, so the 100 g mass is destroyed.
The 100 g mass of ice combines with the mass of the metal sheet.
The ice has evaporated, producing water vapor with a mass of 10 g.
____ 31. In the laboratory, Austin is given a mixture of iron filings, sand, and salt. To separate the mixture, Austin uses
a magnet, boiling water, and a filter. Which statement is true about the process Austin uses to separate this
mixture?
A. Austin uses only physical changes to separate the mixture’s components.
B. Austin uses only chemical changes to separate the mixture’s components.
C. Austin uses both physical and chemical changes to separate the mixture’s components.
D. Austin uses neither physical nor chemical changes to separate the mixture’s components.
____ 32. The graph below shows the states in which water exists.
Review the information in the graph. Which of these statements is true?
A. The change from ice to liquid water is a chemical change.
B. The change from liquid water to water vapor is a physical change.
C. It takes the same amount of time for ice to melt as it does for liquid water to become water
vapor.
D. The change from ice to liquid water to water vapor shows a decrease in mass due to the
changes in states of matter.
____ 33. Which of these statements represents a physical change of matter?
A.
B.
C.
D.
A match is struck and flames.
An old bike is left outside and rust forms.
A pot of water reaches the boiling point.
Fireworks burst into a rainbow of color in the night sky.
____ 34. For his science project, Raul fills four balloons with helium. Each balloon measures 10 cm across at the start.
Raul places each balloon in four different enclosed areas. Over the course of 2 hours, Raul changes the
temperature of the enclosed areas as shown in the graph below.
How does the change of temperature affect the balloons?
A.
B.
C.
D.
As the temperature decreases, all balloons increase in size as the helium gas contracts..
As the temperature increases, all balloons remain the same size.
As the temperature increases, the amount of helium in the balloons doubles.
As the temperature increases, the size of the balloons increases as the helium gas expands.
____ 35. Sara is making dinner. Which of these activities involves a chemical change due to temperature?
A.
B.
C.
D.
peeling potatoes
slicing cucumbers
shredding lettuce
grilling hamburgers
____ 36. Which of these statements describes a typical chemical reaction involving the addition of temperature?
A. The matter always retains the same shape.
B. The product of the reaction has different chemical properties.
C. The product of the reaction conducts both heat and electric current.
D. The starting material can be recovered from a solution.
Grade 8 Physical Posttest
Answer Section
MULTIPLE CHOICE
1. ANS: C
A is incorrect because water in the form of ice does not release energy as it melts. It takes in energy as it melts
to break apart, not form, attractions between the particles.
B is incorrect because water in the form of ice takes in energy to form, not break apart, attractions between
the particles as it melts.
C is correct because ice takes in energy from the surroundings to break apart attractions as it melts between
points 1 and 2.
D is incorrect because as ice melts it takes in, not releases, energy.
STA: SC.8.P.8.1
2. ANS: D
A is incorrect because the motion of liquid particles differs from the motion of gas particles.
B is incorrect because the particles in a liquid slide past each other, and the particles in a gas move randomly
in all directions.
C is incorrect because gas particles move freely and liquid particles can slide past each other.
D is correct because liquid particles can slide past each other, and gas particles move randomly in all
directions.
STA: SC.8.P.8.1
3. ANS: A
A is correct because water can flow because the particles can slide past each other.
B is incorrect because water particles in liquid water are always in motion.
C is incorrect because water particles in a liquid are not locked in one place.
D is incorrect because it is the particles in a gas that move freely in all directions, not the particles in a liquid.
STA: SC.8.P.8.1
4. ANS: B
A is incorrect because the mass does not change.
B is correct because mass is constant, but weight depends on gravitational force.
C is incorrect because the probe weighs less on Mars, where there is less gravitational force.
D is incorrect because mass is constant, and weight decreases as the gravitational force decreases.
STA: SC.8.P.8.2
5. ANS: B
A is incorrect because a balance does not measure density directly.
B is correct because a balance provides a measure of the amount of mass in an object.
C is incorrect because volume is the space an object takes up, which is not measured by the scale.
D is incorrect because weight is measured with scale.
STA: SC.8.P.8.2
6. ANS: D
A is incorrect because the mass of objects does not depend on location.
B is incorrect because a change in weight with location indicates a change in gravitational pull.
C is incorrect because an increase in weight indicates an increase in gravitational pull.
D is correct because weight is the amount of gravitational pull on the mass of an object.
STA: SC.8.P.8.2
7. ANS: A
A is correct because gasoline has the least density, so it occupies the greatest volume for a given mass.
B is incorrect because mercury has the greatest density, so it occupies the least volume for a given mass.
C is incorrect because milk has a greater density than gasoline does, so milk occupies a smaller volume for a
given mass.
D is incorrect because water has a greater density than gasoline does, so water occupies a smaller volume for
a given mass.
STA: SC.8.P.8.3
8. ANS: C
A is incorrect because the density of a solid object does not depend on its shape.
B is incorrect because heavier objects could be larger and have a smaller density.
C is correct because mass and volume can be used to calculate density.
D is incorrect because clear objects, such as glass, can be denser than opaque objects, such as wood.
STA: SC.8.P.8.3
9. ANS: B
A is incorrect because the although the liquids have the same volume, they have different masses.
B is correct because the density of liquid A is 1.1 g/mL and the density of liquid B is 1.0 g/ mL.
C is incorrect because the masses need to be divided by the volumes to find the densities.
D is incorrect because density is not equal to mass times volume.
STA: SC.8.P.8.3
10. ANS: A
A is correct because when two insoluble liquids are mixed, the less dense liquid will float atop the denser
liquid.
B is incorrect because neither liquid mixes well with the other. This choice does not explain why one liquid is
floating on top of the other.
C is incorrect because the reactivity of the liquids plays no role in the result of the experiment. This choice
does not explain why one liquid is floating on top of the other.
D is incorrect because conductivity of the liquids plays no role in the result of the experiment. This choice
does not explain why one liquid is floating on top of the other.
STA: SC.8.P.8.4
11. ANS: A
A is correct because aluminum and copper are metals and can conduct electricity.
B is incorrect because glass is not a good electrical conductor like copper.
C is incorrect because paper is an electrical insulator and copper a conductor.
D is incorrect because wood is not electrically conductive like copper.
STA: SC.8.P.8.4
12. ANS: B
A is incorrect because although solubility depends on temperature, it is not the temperature at which a liquid
changes to a gas.
B is correct because the boiling point is the temperature at which a substance changes from a liquid to a gas.
C is incorrect because at the melting point solids change to liquids and liquids change to solids.
D is incorrect because thermal conductivity is a measure of how well a substance conducts heat.
STA: SC.8.P.8.4
13. ANS: B
A is incorrect because a mixtures always contain more than one type of atom.
B is correct because an element is made up of one type of atom.
C is incorrect because a molecule can be made up of more than one type of atom. A water molecule is an
example of a molecule made up of two types of atom (hydrogen and oxygen).
D is incorrect because a compound is made up of two or more types of atoms that are chemically combined.
STA: SC.8.P.8.5
14. ANS: A
A is correct because all living and nonliving things are made up of combinations of the atoms of elements.
B is incorrect because the other nonliving things and the living things are also made up of atoms of elements.
C is incorrect because the nonliving things are also made up of atoms of elements.
D is incorrect because the living things are also made up of atoms of elements.
STA: SC.8.P.8.5
15. ANS: C
A is incorrect because compounds do not have the same properties as the elements that make them up.
B is incorrect because compounds have different properties than the elements they contain.
C is correct because elements combine to form compounds with new properties.
D is incorrect because carbon dioxide is made of a different combination of carbon and oxygen, and has
different properties.
STA: SC.8.P.8.5
16. ANS: A
A is correct because the atomic numbers, located above the chemical symbol of each element, increase by 1
from left to right within a period.
B is incorrect because the atomic numbers increase by 1 from left to right, not from top to bottom.
C is incorrect because the average atomic masses increase or decrease by varying amounts from left to right
within a period.
D is incorrect because the average atomic masses increase by varying amounts from top to bottom within a
group.
STA: SC.8.P.8.6
17. ANS: B
A is incorrect because gases are found mostly on the right side of the periodic table.
B is correct because the first two rows the periodic table contains reactive metals.
C is incorrect because nonmetals are found on the right part of the periodic table.
D is incorrect because metalloids are on the right-side of the periodic table and are reactive.
STA: SC.8.P.8.6
18. ANS: B
A is incorrect because elements that have larger atomic masses are not all solids.
B is correct because elements in the same column usually have similar properties.
C is incorrect because atomic mass increases going down a column.
D is incorrect because atomic numbers increase going down a column and from left to right across a row.
STA: SC.8.P.8.6
19. ANS: A
A is correct because an atom is the smallest particle of an element that has the chemical properties of that
element.
B is incorrect because a proton from a calcium atom is smaller than an atom and does not have the same
chemical properties of calcium.
C is incorrect because an electron from a calcium atom is smaller than the atom itself and does not have the
same chemical properties of calcium.
D is incorrect because a molecule that contains calcium is larger than an atom of calcium and would have
different properties than calcium.
STA: SC.8.P.8.7
20. ANS: A
A is correct because the atomic number is the number of protons an atom has.
B is incorrect because the mass of the protons and the neutrons is the mass number.
C is incorrect because the atomic number of an atom does not change when it loses or gains an electron.
D is incorrect because the atomic number describes the number of protons, not the mass of the nucleus.
STA: SC.8.P.8.7
21. ANS: C
A is incorrect because the nucleus is the small, dense center of atoms.
B is incorrect because neutrons are small particles that are packed together in the nucleus.
C is correct because most of the volume of the atom is taken up by the cloud of electrons around the nucleus.
D is incorrect because protons are small particles found in the nucleus, which is small compared to the total
size of an atom.
STA: SC.8.P.8.7
22. ANS: A
A is correct because a very high pH means that a compound is highly basic.
B is incorrect because highly acidic compounds have a very low pH.
C is incorrect because slightly basic compounds have a pH slightly above 7.
D is incorrect because slightly acidic compounds have a pH slightly below 7.
STA: SC.8.P.8.8
23. ANS: A
A is correct because the fact that a substance is a strong acid indicates that it has a low pH.
B is incorrect because while clarity is a characteristics of some acids, it is not true of all acids.
C is incorrect because the acidity of a substance does not provide information regarding its density.
D is incorrect because the acidity of a substance does not provide information regarding its melting point.
STA: SC.8.P.8.8
24. ANS: B
A is incorrect because this is the formula of nitric acid, which is a strong acid.
B is correct because this is the formula of sodium hydroxide, which is a strong base.
C is incorrect because this is the formula of sulfuric acid, which is a strong acid.
D is incorrect because this is the formula of acetic acid, which is a weak acid.
STA: SC.8.P.8.8
25. ANS: D
A is incorrect because you would probably see tiny particles in both liquids if they were suspensions.
B is incorrect because you would not see tiny particles floating in a solution.
C is incorrect because you see tiny particles floating in B, not A, so A is not a suspension, and B is not a
solution.
D is correct because a solution would be homogeneous, like A, while a suspension would show tiny particles,
like B.
STA: SC.8.P.8.9
26. ANS: D
A is incorrect because neither salt or pepper are metallic.
B is incorrect because a mixture of sand and water is best separated by filtering.
C is incorrect because a mixture of sand and pebbles is best separated by removing the pebbles by hand or
passing the mixture through a sieve.
D is correct because iron filings would be attracted to the magnet, while salt would not.
STA: SC.8.P.8.9
27. ANS: C
A is incorrect because a pure substance can contain more than one type of element, such as the container of
ammonia gas.
B is incorrect because compounds such as ammonia are pure substances, but can be decomposed into
elements.
C is correct because a pure substance can be an element or a compound, which is a substance with two or
more elements chemically combined. Ammonia is a compound, so it is a pure substance. However, the second
flask contains two different substances that are not chemically combined.
D is incorrect because this statement explains why a substance cannot be classified as an element rather than a
pure substance.
STA: SC.8.P.8.9
28. ANS: A
A is correct because although mass is conserved in a chemical reaction, the evolution of a gas would explain
the decrease in mass.
B is incorrect because the evolution of a gas, not vinegar’s evaporation, caused the decrease in mass.
C is incorrect because mixtures are not less massive than their parts.
D is incorrect because when baking soda and vinegar are mixed, mass is not destroyed. Instead, the evolution
of a gas caused the decrease in mass.
STA: SC.8.P.9.1
29. ANS: A
A is correct because the mass of the sugar plus the mass of the water equals the mass of the sugar solution.
B is incorrect because the difference between the total mass of 67 g and the 56 g of water is 11.
C is incorrect because 56 g is the amount of water not sugar.
D is incorrect because 123 is the mass of the water and the sugar solution, not the difference between the
sugar solution and the water.
STA: SC.8.P.9.1
30. ANS: A
A is correct because mass is not created or destroyed because of a physical change.
B is incorrect because mass cannot be created or destroyed.
C is incorrect because the mass of ice does not combine with the metal sheet.
D is incorrect because the mass of water vapor will equal the mass of the original ice.
STA: SC.8.P.9.1
31. ANS: A
A is correct because separation by magnetism, boiling point, and filtration based on particle size are all
examples of physical changes.
B is incorrect because separation by magnetism, boiling point, and filtration based on particle size are all
examples of physical changes, not chemical changes.
C is incorrect because separation by magnetism, boiling point, and filtration based on particle size are all
examples of physical changes.
D is incorrect because separation by magnetism, boiling point, and filtration based on particle size are all
examples of physical changes.
STA: SC.8.P.9.2
32. ANS: B
A is incorrect because ice changing to water is a physical change.
B is correct because a change in state is a physical change.
C is incorrect because there is no accurate representation of time on the chart.
D is incorrect because there is no indication having to do with mass on the chart.
STA: SC.8.P.9.2
33. ANS: C
A is incorrect because burning is a chemical process.
B is incorrect because rusting is a chemical process.
C is correct because boiling represents a physical change.
D is incorrect because fireworks exploding are a chemical change.
STA: SC.8.P.9.2
34. ANS: D
A is incorrect because the balloons increase in size as the temperatures increase.
B is incorrect because the balloons increase in size as the temperatures increase.
C is incorrect because the amount of helium does not change.
D is correct because the balloons increase in size as the temperatures increase..
STA: SC.8.P.9.3
35. ANS: D
A is incorrect because peeling does not change the matter in potatoes.
B is incorrect because slicing does not change the matter in cucumbers.
C is incorrect because shredding does not change the matter in lettuce.
D is correct because grilling causes a chemical change in the hamburgers.
STA: SC.8.P.9.3
36. ANS: B
A is incorrect because a chemical change produces a substance with different physical and chemical
properties.
B is correct because matter changes in a chemical reaction.
C is incorrect because only some substances can conduct heat or electric current. Not all chemical reactions
produce these types of substances.
D is incorrect because the ability to be recovered is a physical property.
STA: SC.8.P.9.3