ACT Science Review Questions
A - Answer A certain type of bottom-dwelling microorganism thrives under the following
environmental conditions: low concentrations of Fe2+, high concentrations of O2, and a
neutral pH. Based on the table, at which of the following sediment depths would one
most likely find this microorganism?
A. 0 cm
B. 5 cm
C. 10 cm
D. 15 cm
B - Answer If the trends indicated in the table were to continue, one would predict the
pH of the sediments at a depth of 35 cm to be:
A. 1.5.
B. 3.5.
C. 4.5.
D.6.0.
C - Answer The graph and chart above best represents the relationship between
concentration and sediment depth for which of the following ions and dissolved gases?
A. Ferrous iron (Fe2+)
B. Oxygen (O2)
C. Carbon dioxide (CO2)
D. Sulfate (SO42-)
Correct answer is C. The other options describe processes that would not enable you to
determine whether or not the solution was supersaturated: you would observe the same
thing either way. Supersaturated solutions are not stable. If you add more solute (in this
case the crystal) to a supersaturated solution, the extra solute will precipitate out of the
solution, indicating that the solution was indeed supersaturated. - Answer To determine
whether a water solution of Na2S2O3 at room temperature is supersaturated, one can
(A) heat the solution to its boiling point
(B) add water to the solution
(C) add a crystal of Na2S2O3 to the solution
(D) acidify the solution
(E) cool the solution to its freezing point
D - Answer According to the information provided in the table, the concentration of
which of the following ions and dissolved gases is constant for sediment depths of 10
cm or more?
a. Sulfide (S2-)
b. Carbon dioxide (CO2)
c. Ferric iron (Fe3+)
d. Oxygen (O2)
,D - Answer According to the information provided in the table, the concentration of
which of the following ions and dissolved gases is constant for sediment depths of 10
cm or more?
a. Sulfide (S2-)
b. Carbon dioxide (CO2)
c. Ferric iron (Fe3+)
d. Oxygen (O2)
F is correct
By inspection, one can see that, at a depth of 0 cm, the concentration of Fe2+ is lowest
(0.5 ppm), the concentration of O2 is highest (2.0), and pH is neutral (7.0). - Answer
Passage I
The following table represents the concentration of ions and dissolved gases in the
sediment at the bottom of an ocean. A depth of 0 centimeters (cm) represents the top of
the sediment. The concentrations are expressed in parts per million (ppm). The acidity
of a solution is represented on a scale known as pH. A pH of 1 is very acidic, a pH of 7
is neutral, and a pH of 14 is very basic.A certain type of bottom-dwelling microorganism
thrives under the following environmental conditions: low concentrations of Fe2+, high
concentrations of O2, and a neutral pH. Based on the table, at which of the following
sediment depths would one most likely find this microorganism?
F. 0 cm
G. 5 cm
H. 10 cm
J. 15 cm
The best answer is H. Figure 3 indicates the number of trees that are present as a
function of the age of a stand for both pine trees and oak-hickory trees.
According to Figure 3, the oak-hickory trees reach a density of 13,000 trees per unit
area after approximately 150 years and a density of 15,000 trees per unit area after
approximately 160 years. Thus, H is the correct answer. - Answer Abandoned cornfields
have been the sites of investigations concerning ecological succession, the orderly
progression of changes in the plant and/or animal life of an area over time (see Figure
1).
(Note: The plants are ordered according to their appearance during ecological
succession.)
During the early stages of succession, the principal community (living unit) that
dominates is the pioneer community. Pioneer plants are depicted in Figure 2.
The final stage of ecological succession is characterized by the presence of the climax
community, the oak-hickory forest. Figure 3 depicts the gradual change from pine to
hardwoods.
, According to the information in Figure 3, a 150-year-old climax community would
contain oak and hickory trees with a density of approximately:
F. 3,000 trees per unit area.
G. 5,000 trees per unit area.
H. 15,000 trees per unit area.
J. 20,000 trees per unit area.
The change in the object's momentum is 2mV0 directed to the left. Momentum is a
vector quantity. Its magnitude for an object of mass m and speed V is mV. Taking the
positive direction to be to the right (the initial direction of the object), the object has
momentum +V0 before striking the wall and momentum -mV0 afterward. The change in
momentum is the final value minus the initial value: -mV0 - (+mV0) = -2mV0
This is a change of magnitude 2mV0 directed to the left. - Answer An object with mass
m and speed V0 directed to the right strikes a wall and rebounds with speed V0 directed
to the left.
The change in the object's momentum is
A.2mV0 Directed to the left
B. MV0 Directed to the left
C. Zero
D. MV0 Directed to the right
E. 2mV0 Directed to the right
The correct answer is (A). Without friction, there is still a constant force on the block.
This means a constant acceleration, so the speed curve will still be a straight line.
Removing friction will not cause the block to be in motion before it is pulled, so the initial
speed remains zero. Finally, since friction would act against the pulling force, the net
force on the block is greater without friction, so the acceleration and thus the slope of
the speed graph would be greater - Answer A block is pulled along a horizontal surface
with a constant horizontal force of magnitude F. The surface exerts a frictional force of
constant magnitude f on the block. The graph of speed V as a function of time t for the
block is shown above.
If, instead, the block slides without friction but is pulled with the same horizontal force of
magnitude F, which of the following would be a possible new graph of speed V as a
function of time t? (The dashed line represents the old graph.)
The correct answer is (B), a constant acceleration. At each instant the acceleration is
the slope of the velocity graph. Since the velocity curve is a straight line that has
constant slope, the acceleration is constant. Alternately, the description indicates that
both the force pulling the block and the frictional force are constant. Acceleration is
force divided by mass, so it also must be constant. - Answer A block is pulled along a
horizontal surface with a constant horizontal force of magnitude F. The surface exerts a
A - Answer A certain type of bottom-dwelling microorganism thrives under the following
environmental conditions: low concentrations of Fe2+, high concentrations of O2, and a
neutral pH. Based on the table, at which of the following sediment depths would one
most likely find this microorganism?
A. 0 cm
B. 5 cm
C. 10 cm
D. 15 cm
B - Answer If the trends indicated in the table were to continue, one would predict the
pH of the sediments at a depth of 35 cm to be:
A. 1.5.
B. 3.5.
C. 4.5.
D.6.0.
C - Answer The graph and chart above best represents the relationship between
concentration and sediment depth for which of the following ions and dissolved gases?
A. Ferrous iron (Fe2+)
B. Oxygen (O2)
C. Carbon dioxide (CO2)
D. Sulfate (SO42-)
Correct answer is C. The other options describe processes that would not enable you to
determine whether or not the solution was supersaturated: you would observe the same
thing either way. Supersaturated solutions are not stable. If you add more solute (in this
case the crystal) to a supersaturated solution, the extra solute will precipitate out of the
solution, indicating that the solution was indeed supersaturated. - Answer To determine
whether a water solution of Na2S2O3 at room temperature is supersaturated, one can
(A) heat the solution to its boiling point
(B) add water to the solution
(C) add a crystal of Na2S2O3 to the solution
(D) acidify the solution
(E) cool the solution to its freezing point
D - Answer According to the information provided in the table, the concentration of
which of the following ions and dissolved gases is constant for sediment depths of 10
cm or more?
a. Sulfide (S2-)
b. Carbon dioxide (CO2)
c. Ferric iron (Fe3+)
d. Oxygen (O2)
,D - Answer According to the information provided in the table, the concentration of
which of the following ions and dissolved gases is constant for sediment depths of 10
cm or more?
a. Sulfide (S2-)
b. Carbon dioxide (CO2)
c. Ferric iron (Fe3+)
d. Oxygen (O2)
F is correct
By inspection, one can see that, at a depth of 0 cm, the concentration of Fe2+ is lowest
(0.5 ppm), the concentration of O2 is highest (2.0), and pH is neutral (7.0). - Answer
Passage I
The following table represents the concentration of ions and dissolved gases in the
sediment at the bottom of an ocean. A depth of 0 centimeters (cm) represents the top of
the sediment. The concentrations are expressed in parts per million (ppm). The acidity
of a solution is represented on a scale known as pH. A pH of 1 is very acidic, a pH of 7
is neutral, and a pH of 14 is very basic.A certain type of bottom-dwelling microorganism
thrives under the following environmental conditions: low concentrations of Fe2+, high
concentrations of O2, and a neutral pH. Based on the table, at which of the following
sediment depths would one most likely find this microorganism?
F. 0 cm
G. 5 cm
H. 10 cm
J. 15 cm
The best answer is H. Figure 3 indicates the number of trees that are present as a
function of the age of a stand for both pine trees and oak-hickory trees.
According to Figure 3, the oak-hickory trees reach a density of 13,000 trees per unit
area after approximately 150 years and a density of 15,000 trees per unit area after
approximately 160 years. Thus, H is the correct answer. - Answer Abandoned cornfields
have been the sites of investigations concerning ecological succession, the orderly
progression of changes in the plant and/or animal life of an area over time (see Figure
1).
(Note: The plants are ordered according to their appearance during ecological
succession.)
During the early stages of succession, the principal community (living unit) that
dominates is the pioneer community. Pioneer plants are depicted in Figure 2.
The final stage of ecological succession is characterized by the presence of the climax
community, the oak-hickory forest. Figure 3 depicts the gradual change from pine to
hardwoods.
, According to the information in Figure 3, a 150-year-old climax community would
contain oak and hickory trees with a density of approximately:
F. 3,000 trees per unit area.
G. 5,000 trees per unit area.
H. 15,000 trees per unit area.
J. 20,000 trees per unit area.
The change in the object's momentum is 2mV0 directed to the left. Momentum is a
vector quantity. Its magnitude for an object of mass m and speed V is mV. Taking the
positive direction to be to the right (the initial direction of the object), the object has
momentum +V0 before striking the wall and momentum -mV0 afterward. The change in
momentum is the final value minus the initial value: -mV0 - (+mV0) = -2mV0
This is a change of magnitude 2mV0 directed to the left. - Answer An object with mass
m and speed V0 directed to the right strikes a wall and rebounds with speed V0 directed
to the left.
The change in the object's momentum is
A.2mV0 Directed to the left
B. MV0 Directed to the left
C. Zero
D. MV0 Directed to the right
E. 2mV0 Directed to the right
The correct answer is (A). Without friction, there is still a constant force on the block.
This means a constant acceleration, so the speed curve will still be a straight line.
Removing friction will not cause the block to be in motion before it is pulled, so the initial
speed remains zero. Finally, since friction would act against the pulling force, the net
force on the block is greater without friction, so the acceleration and thus the slope of
the speed graph would be greater - Answer A block is pulled along a horizontal surface
with a constant horizontal force of magnitude F. The surface exerts a frictional force of
constant magnitude f on the block. The graph of speed V as a function of time t for the
block is shown above.
If, instead, the block slides without friction but is pulled with the same horizontal force of
magnitude F, which of the following would be a possible new graph of speed V as a
function of time t? (The dashed line represents the old graph.)
The correct answer is (B), a constant acceleration. At each instant the acceleration is
the slope of the velocity graph. Since the velocity curve is a straight line that has
constant slope, the acceleration is constant. Alternately, the description indicates that
both the force pulling the block and the frictional force are constant. Acceleration is
force divided by mass, so it also must be constant. - Answer A block is pulled along a
horizontal surface with a constant horizontal force of magnitude F. The surface exerts a
