Grade 8 Science Practice Test Answer Key Question 1 ... · Grade 8 Science Practice Test Answer Key...

Grade 8 Science Practice Test Answer Key

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Question 1

Reporting Category: Scientific Process

Benchmark: SC.8.1.1 Determine the link(s) between evidence and the conclusion(s) of an

investigation

Answer Key: A

A student comparing the effectiveness of two types of fertilizer plants two bean seeds in separate pots of equal size. Equal amounts of each type of fertilizer, X and Y, are added to each pot. The plants are then placed in the sun and watered equal amounts for four weeks. At the end of each week, the student measures the height of each plant and records her data in the table shown.

According to the data, what conclusion can be made about the fertilizers?

A. Fertilizer X causes plants to grow at a faster rate than Fertilizer Y.

This answer is correct. The data show that a plant given Fertilizer X will grow faster than one given Fertilizer Y.

B. Fertilizer X increases the amount of leaves on the plant.

This answer is not correct. This is a conclusion that cannot be drawn about how Fertilizer X affects leaf production from the data collected.

C. Fertilizer Y causes plants to grow more root hairs than Fertilizer X.

This answer is not correct. The student did not record any data on the number of root hairs grown by each plant. Therefore, a conclusion cannot be drawn about how the fertilizers affect root hair growth.

D. Fertilizer Y increases the amount of carbon dioxide plants can take in.

This answer is not correct. The student did not measure how much carbon dioxide was absorbed by either plant. Therefore, a conclusion cannot be drawn about how either fertilizer affects carbon dioxide absorption.


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Question 2

Reporting Category: Scientific Process Benchmark: SC.8.1.1 Determine the link(s) between evidence and the conclusion(s) of an investigation Answer Key: B A student follows this procedure to investigate the relationship between sunlight and the evaporation of water:

1. Fill two 25 cm x 25 cm pans with water to a depth of 2 cm. 2. Leave one pan in the direct sunlight. Leave one pan in a dark closet. 3. After three hours, measure the depth of the water in each pan.

After completing the procedure, the student summarizes the data in a table and concludes that sunlight increases the rate at which water evaporates.

Which statement best connects the test results and the conclusion?

A. More water molecules from the pan in the closet changed from their liquid state to a gas.

This answer is not correct. Less water evaporated from the pan in the closet than from the pan in the sun.

B. More water evaporated in the sunlight than in the closet in the same amount of time.

This answer is correct. The data show that less water was left in the pan in the sunlight and, therefore, more water evaporated in the sunlight in the same amount of time. This statement directly explains the link between the data and the conclusion.


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C. The pan in the closet had 1 more centimeter of water than the pan in the sunlight.

This answer is not correct. Although this calculation is correct, it does not explain the link between the data and the conclusion.

D. The same amount of water was added to each pan at the beginning of the investigation.

This answer is not correct. The addition of the same amount of water to each pan is important in the data analysis, but it does not directly explain the link between the data and the conclusion.


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Question 3


Benchmark: SC.8.1.2 Communicate the significant components of the experimental design and results of a scientific investigation Answer Key: A A scientist studying earthquake activity around Hawai‘i collects the data shown in the table.

How can the data be presented to show whether earthquakes are occurring at a higher frequency?

A. Display the number of earthquakes per day on a bar graph.

This answer is correct. The number of earthquakes per day is earthquake frequency. Displaying this number for each day on a bar graph will reveal frequency trends.

B. Locate the earthquakes on a map using their latitude and longitude.

This answer is not correct. Locating the earthquakes on a map provides no information about time, so it provides no information about frequency.


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C. Plot earthquake magnitude vs. depth on a graph.

This answer is not correct. Plotting earthquake magnitude versus depth provides no information about time, so it provides no information about frequency.

D. Sort the rows of the table by earthquake magnitude.

This answer is not correct. Sorting the rows of the table by earthquake magnitude preserves the time information needed to investigate frequency, but does not present this information in a useful way.


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Question 4


Benchmark: SC.8.1.2 Communicate the significant components of the experimental design and results of a scientific investigation Answer Key: C Scientists have studied a mountain gorilla population for several years. In 2007, the population size was 72 individuals. In 2009, the population size was 81 individuals.

Which mathematical calculation would be most appropriate in helping scientists analyze the rate at which the population grew?

A. Add the 2007 and 2009 population sizes.

This answer is not correct. Adding the populations does not provide useful information.

B. Average the 2007 and 2009 population sizes.

This answer is not correct. The average population would not be helpful for understanding growth rate.

C. Calculate the percent change between the 2007 and 2009 population sizes.

This answer is correct. The percent change is the most meaningful measure of the difference between the population sizes. Dividing by the time will yield a growth rate.

D. Determine the difference between the 2007 and 2009 population sizes.

This answer is not correct. The growth rate can be expressed in terms of the difference, but it is more meaningful to incorporate the population size, as when calculating the percent difference.


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Question 5


Benchmark: SC.8.1.2 Communicate the significant components of the experimental design and results of a scientific investigation Answer Key: C A student considers the following question: Does the moon’s phase affect the time of day that the moon rises? She cannot observe the moon rising so she plans another way to answer the question. She will observe the moon at the same time every day for three months. She will record the date and make a drawing of the moon phase in a notebook. Which additional piece of information will she need to answer her question?

A. The amount of time it takes to make each observation of the moon

This answer is not correct. The amount of time it takes to make an observation will not affect the results of the study.

B. The location on Earth where she makes each observation of the moon

This answer is not correct. The location on Earth where the student makes the observation is not likely to vary enough to affect her results.

C. The position of the moon in the sky for each observation of the moon

This answer is correct. Because the student will observe the moon at the same time every day, she can tell whether the moon rises earlier or later each day by comparing its position in the sky on each day.

D. The time of sunset each day she makes an observation of the moon

This answer is not correct. The moon rises at different times each day; its cycle is not tied to the time of sunset.


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Question 6


Benchmark: SC.8.2.1 Describe significant relationships among society, science, and technology and how one impacts the other. Answer Key: C

Scientists are able to study all of Earth’s surface using electromagnetic radiation and special cameras on satellites. This is called remote sensing. Before remote sensing provided this data, scientists had to hike, drive, or fly airplanes over hard-to-reach areas.

Which is a benefit of using remote sensing instead of older technologies?

A. Scientists are able to draw conclusions without having to analyze data.

This answer is not correct. Conclusions must be based on the analysis of data. Evidence must support a conclusion even if data was gathered using a new type of technology.

B. Scientists are able to predict earthquakes in distant locations.

This answer is not correct. Earthquakes cannot be reliably predicted, even with satellites.

C. Scientists can analyze more data and spend less time collecting data.

This answer is correct. Satellites allow scientists to use the large amounts of data gathered by a satellite without spending a lot of time collecting the data in person.

D. Scientists can study layers beneath Earth’s surface more easily.

This answer is not correct. The satellites described above gather information about Earth’s

surface.


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Question 7


Benchmark: SC.8.2.1 Describe significant relationships among society, science, and technology and how one impacts the other Some escalators are being replaced with “variable speed” escalators that can detect when a person approaches. If the escalator has no passengers, it slows to a low speed. When a passenger steps on the escalator, it returns to its normal running speed.

Using the “Connect Line” button, draw a line on the graph to show how replacing regular escalators with those that have the variable speed feature is likely to affect the amount of electricity needed to power escalators.

Draw only one line. Start your line at point S.

Answer Key:

2 points

For this item, a full-credit response includes

a line with a downward slope (1 point) AND

the line not extending all the way down to zero (1 point).

1 point For this item, a partial-credit response includes

a line with a downward slope that touches the x-axis (1 point).

Note: If the student draws a line with a positive slope, he/she will not earn a point for drawing a line that does not extend all the way down to zero. The only way to earn the second point is to draw a line with a negative slope.


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Sample Student Answer:

Explanation of Correct Answer:

The amount of electricity these escalators use when there are no passengers is small relative to the regular escalators that run at a constant speed, whether they have passengers or not. As the number of regular escalators being replaced by variable speed escalators increases, the amount of electricity needed to run the escalators decreases. The variable speed escalators run at a slow speed when they are not used. They do not stop. Even when the variable speed escalators are not being used, they are still running and using electricity


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Question 8


Benchmark: SC.8.2.2 Describe how scale and mathematical models can be used to support and explain scientific data. Answer Key: C

For fifty years beginning in 1940, volunteers counted the number of birds in different habitats around Honolulu for one day each year. The graph shows the data for the annual bird count during this time.

Which statement best describes the trend in the data from 1940 to 1990?

A. The number of birds seen increased exponentially, doubling about each decade.

This answer is not correct. If the number of birds seen increased exponentially by doubling each decade, the trend line would show about 50 birds in 1950, 100 birds in 1960, 200 birds in 1970, etc.

B. The number of birds seen increased exponentially, doubling about every 20 years.

This answer is not correct. If the number of birds seen increased exponentially by doubling every 20 years, the trend line would show about 50 birds in 1960, 100 in 1980, etc.


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C. The number of birds seen increased steadily at a rate of about 30 birds per decade.

This answer is correct. The trend line through the average of the points on the graph shows a steady growth rate of about 30 birds per decade.

D. The number of birds seen increased steadily at a rate of about 50 birds per decade.

This answer is not correct. If the number of birds increased at a steady growth rate of 50 birds per decade, the trend line would show 50 birds in 1950, 100 birds in 1960, 150 birds in 1970, etc.


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Question 9

Reporting Category: The Solar System & The Universe Benchmark: SC.8.8.6: Explain the relationship between density and convection currents in the ocean and atmosphere Students create the classroom model shown in the diagram. A cup of dyed ice water is attached to the inside of a tank filled with water at 30° C. The ice water flows into the tank through a small hole in the bottom of the cup, as shown.

Select the two large systems the students can investigate using this model.

A. Density Currents

This answer is correct. The investigation allows students to model density currents as colder, denser water sinks, warms, and then rises as less dense water.

B. Global wind current patterns

This answer is correct. Because air with different densities and temperatures produces convection currents in the atmosphere, the model can be used to investigate global wind current patterns.


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C. Ocean water biomes

This answer is not correct. The investigation models convection currents produced by differing densities of water, not ecosystems within the ocean.

D. Temperature profile of ocean water

This answer is not correct. While the investigation deals with different temperatures, it does not deal with the temperature strata in ocean water.

E. Upwelling of water currents

This answer is not correct. The investigation models convection currents produced by differing densities of water, not the replacement of surface water, which has been pushed away by wind, with water from beneath the surface.


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Question 10


Benchmark: SC.8.2.2 Describe how scale and mathematical models can be used to support and explain scientific data Answer Key: B

Students make a model of the solar system. They want the objects in their model to correctly represent the size relationships of objects in the solar system. The ratio of the diameter of the sun to the diameter of Earth is approximately 100:1.

Which items would best represent the sun and Earth in the students’ model?

A.

This answer is not correct. The ratio of a basketball to a baseball is roughly 3:1.

B.

This answer is correct. The ratio of a beach ball to a pea is roughly 100:1.


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C.

This answer is not correct. The ratio of a grapefruit to a marble is roughly 10:1.

D.

This answer is not correct. The ratio of an orange to a grape is roughly 3:1.


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Question 11


Benchmark: SC.8.2.2 Describe how scale and mathematical models can be used to support

and explain scientific data.

Students are investigating properties of four different planets. To do this, the students use four different spheres, which each have properties similar to each of the four planets. They investigate the density, diameter, mass, orbital velocity relative to Earth, and rotational period of each planet.

Set up an investigation to determine the relative gravitational force exerted by each planet on other objects using the lowest number of trials.

Answer Key:

A trial is run for each planet using “Mass” as the property.


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A planet’s gravitational pull is determined by the mass of that planet. This investigation calls for each planet to be tested.


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Question 12

Reporting Category: Biological & Physical Sciences

Benchmark: SC.8.5.1 Describe how changes in the physical environment affect the survival of

organisms

Answer Key: A

Humans accidentally introduced a new predator into an ecosystem. It began to act as an

invasive species by preying on a native animal.

Which graph shows what would have happened to the invasive species in this new ecosystem?

A.

This answer is correct. The population of the introduced species would start off small and

then increase because of the available food source.


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B.

This answer is not correct. The population of the invasive species would have started out much

lower and then increased.

C.

This answer is not correct. The population of the invasive species would start low and then

increase since there was an available food source.


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D.

This answer is not correct. The population of the invasive species would have started out

low and then increased.


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Question 13


Benchmark: SC.8.5.1: Describe how changes in the physical environment affect the survival of organisms

Answer Key: C Answer Key (Part II): A; D; E

Part A

The Hawaiian stilt was once a common bird on all the major islands in Hawai‘i. Today, the bird is on the endangered species list. Some information about the Hawaiian stilt is shown in the table.

Information About the Hawaiian Stilt

Predators of the Hawaiian Stilt

Organisms Consumed by the Hawaiian Stilt

Habitat and Behavior of the Hawaiian Stilt

Non-native species such as dogs, cats, and mongooses

Worms Crabs Small fishes

A. Aquatic habitats with low levels of water (about 13 cm)

Which graph represents the results of successful intervention to preserve the Hawaiian stilt population?

A.

This answer is not correct. Successful human intervention will cause an increase in the population of the bird, not an increase and then a decrease.


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B.

This answer is not correct. Successful human intervention will cause an increase in the population of the bird, not minor increases and decreases.

C.

This answer is correct. Successful human intervention will cause an increase in the population of the bird.

D.

This answer is not correct. Successful human intervention will cause an increase in the population of the bird, not a decrease.


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Part B

Select the intervention(s) that could result in the trend of the graph you chose in Part A.

A. Habitat restoration

This answer is correct. This is a conservation effort that will protect the species and help their population increase.

B. Introduction of invasive species

This answer is not correct. This is not a conservation effort and will harm the species, causing a decrease in the population due to competition and predation.

C. Land use development

This answer is not correct. This is not a conservation effort and will harm the habitats of the species, causing a decrease in the population.

D. Pollution control


E. Wetland conservation



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Question 14

Reporting Category: Biological & Physical Sciences Benchmark: SC.8.6.1 Explain the relationship between the color of light and wavelength within the electromagnetic spectrum Answer Key: D Which diagram correctly orders different colors of light according to the value of a property? A.

This answer is not correct. The color of light is unrelated to its amplitude. B.

This answer is not correct. The color of light is unrelated to its amplitude. C.

This answer is not correct. Red light has a longer wavelength than blue light. D.

This answer is correct. Red light has a longer wavelength than blue light.


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Question 15

Reporting Category: The Solar System & The Universe

Benchmark: SC.8.8.8: Describe the composition of objects in the galaxy

Select the frequency and wavelength of each color of light.

Answer Key:


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Question 16


Benchmark: SC.8.6.3 Identify the characteristics and properties of mechanical and

electromagnetic waves

Answer Key: D

The diagram shows the locations of several students and two mirrors.

• Student P is standing in Room 1 looking into Room 2.

• Student R is standing in Room 2. There are two mirrors in Room 2.

• Student Q and Student S are in Room 3.

Student P can see one student in Mirror M.

Which student can Student P see in Mirror M?

A. Student P

This answer is not correct. Student P cannot see himself in the mirror because the mirror is

tilted away from him. The mirror would need to be facing Student P so that the light hits the

mirror and is reflected straight back to Student P’s eyes.

B. Student Q

This answer is not correct. Student Q is not visible to Student P because there is a wall

between Student Q and the lower mirror. The light reflecting off the mirror cannot travel

through or reflect off the wall.


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C. Student R

This answer is not correct. Student R is not visible to Student P because there is a wall

between them and light would not go from Student R to either mirror and enter the eyes of

Student P because of the mirrors' locations and tilt. The light reflecting off the mirror cannot

travel through or reflect off the wall.

D. Student S

This answer is correct. Light from Student S goes to the right, hits the lower mirror, goes

up, hits the upper mirror, goes left, and enters Student P’s eyes.


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Question 17


Benchmark: SC.8.6.3 Identify the characteristics and properties of mechanical and electromagnetic waves Answer Key: B Which characteristic of a sound wave corresponds to amplitude?

A. Frequency

This answer is not correct. Frequency is the number of complete cycles passing a given point in a time period.

B. Loudness

This answer is correct. Amplitude is the air pressure change. The greater the air pressure change, the louder the sound.

C. Pitch

This answer is not correct. Pitch is related to frequency.

D. Wavelength

This answer is not correct. Wavelength is the distance between one wave crest and the next.


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Question 18–20 Simulation

Students are investigating the behavior of sound waves through different mediums. To do this, the students use sensors to detect the length of time it takes for sound to enter and exit a given medium. They investigate two factors: distance and type of the medium.


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Explanation of How to Use Simulation: The student can choose one of six mediums from the Medium drop down menu:

Air

Aluminum

Hydrogen

Lead

Water (5C)

Water (25C) The student can choose one of three distances (in meters) from the Object Distance drop‒down menu:

1

2

3

After choosing a medium and a distance, the student presses the green “Start” button. An animation of the sound waves plays and the output table populates with the information shown, depending on the indicator and sample chosen.

Medium Distance from sound (m)

Time for sound to reach sensor (sec)

Time for sound to exit material (sec)

Total time (s) Velocity of sound

Air 1 0.0028 None 0.0028 356

Air 2 0.0056 None 0.0056 356

Air 3 0.0084 None 0.0084 356

Aluminum 1 0.0028 0.0016 0.0044 6420

Aluminum 2 0.0056 0.0016 0.0072 6420

Aluminum 3 0.0084 0.0016 0.0100 6420

Hydrogen 1 0.0008 None 0.0008 1310

Hydrogen 2 0.0015 None 0.0015 1310

Hydrogen 3 0.0023 None 0.0023 1310

Lead 1 0.0028 0.0051 0.0079 1960

Lead 2 0.0056 0.0051 0.0107 1960

Lead 3 0.0084 0.0051 0.0135 1960

Water (5C) 1 0.0028 0.0070 0.0098 1427

Water (5C) 2 0.0056 0.0070 0.0126 1427

Water (5C) 3 0.0084 0.0070 0.0154 1427

Water (25C) 1 0.0028 0.0067 0.0095 1497

Water (25C) 2 0.0056 0.0067 0.0123 1497

Water (25C) 3 0.0084 0.0067 0.0151 1497

*Times that are negligible or extremely short are reported as “None” in the simulation.


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Question 19


Benchmark: SC.8.6.3 Identify the characteristics and properties of mechanical and electromagnetic waves

A student records her data in a laboratory notebook and ranks the relative speed of sound for each phase of matter.

Fill in the table with numbers 1, 2, and 3 to rank the relative speed of sound for each phase of matter, with 1 being the fastest and 3 being the slowest.

Answer Key:

Substance

Relative Ranking of Speed of Sound

Gas 3

Solid 1

Liquid 2

For this item, a full-credit response includes

A correct ordering of Gas = 3, Liquid = 2, Solid = 1 (1 point).


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Question 20


Benchmark: SC.8.6.3 Identify the characteristics and properties of mechanical and electromagnetic waves Answer Key: B; D

Select the two graphs that show the relationship between variables when sound travels through

a liquid.


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A.

This answer is not correct. The speed of sound does not increase with distance; it remains constant.

B.

This answer is correct. The speed of sound is constant no matter the distance.

C.

This answer is not correct. The speed of sound does not decrease with distance; it remains constant.


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D.

This answer is correct. The speed of sound increases as the temperature increases for a given state of matter.

E.

This answer is not correct. The speed of sound does not remain constant with varied temperature; it will increase.

F.

This answer is not correct. The speed of sound does not decrease with an increase in temperature for a given state of matter; it will increase.


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Question 21 Reporting Category: The Solar System & The Universe Benchmark: SC.8.8.2 Illustrate the rock cycle and explain how igneous, metamorphic, and sedimentary rocks are formed Answer Key: B A rock is pushed deep underground in an area where mountain-building is occurring, and undergoes the following processes.

First, the rock experiences high pressure that causes its minerals to align themselves in bands.

Second, the rock is pushed further underground and completely melts, then erupts from a volcano and hardens.

Third, the rock is broken down by wind and water into small particles, which flow into a river and get compressed into rock.

Which order correctly shows this progression of rock types? A.

This answer is not correct. The first stage is metamorphic and the second stage is igneous.

B.

This answer is correct. The rock formed from high pressure is metamorphic, the rock formed from the volcano is igneous, and the last process causes it to be sedimentary.

C.

This answer is not correct. The second stage is igneous and the third stage is sedimentary.

D.

This answer is not correct. The first stage is metamorphic and the third stage is sedimentary.


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Question 22


Benchmark: SC.8.8.2 Illustrate the rock cycle and explain how igneous, metamorphic, and sedimentary rocks are formed

The diagram shows two tectonic plates moving toward each other. The white arrows show the direction of plate motion. Igneous rocks, metamorphic rocks, and sedimentary rocks form at different locations.

Move each rock type into a location in the diagram where it would form.

You will only need to fill in three of the blank boxes.

Answer Key:

3 points For this item, a full-credit response includes any three of the following 6 correct answers

Assuming that boxes are numbered 1‒6 clockwise from upper left,

igneous rock type placed in location 3 or 6 (1 point). AND

metamorphic rock type placed in location 2 or 5 (1 point) AND

sedimentary rock type placed in location 1 or 4 (1 point).

2 points Two of the three above.

1 point One of the three above.


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The boxes on the diagram are numbered 1‒6 from the upper left, moving clockwise. Igneous

rocks form when magma cools. Magma was present and cooled at the third and sixth locations

in the diagram. Metamorphic rocks form due to high temperatures and pressure. Locations two

and five are location where both of these factors exist. Sedimentary rocks form on Earth’s

surface from deposits by water or wind. Locations one and four meet these conditions.


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Question 23


Benchmark: SC.8.8.3 Describe how the Earth’s motions and tilt on its axis affect the seasons

and weather patterns

Answer Key: B

The diagram below shows the tilt of Earth’s axis while Earth is in a certain position in its orbital

path around the sun.

In this diagram, what season is it in the northern hemisphere?

A. Spring

This answer is not correct. As the Earth revolves around the sun, Earth’s axis always points

toward the North Star. Thus, during revolution, the North Pole sometimes points toward or

away from the sun. As the Earth travels around the sun and the North Pole is beginning to

point toward the sun, the Northern Hemisphere experiences spring.

B. Summer

This answer is correct. When the North Pole is pointing toward the sun, the sun’s rays

strike the Northern Hemisphere more directly. When the sun’s rays strike the Northern

Hemisphere directly, the region experiences the summer season.

C. Fall

This answer is not correct. As the Earth travels around the sun and the North Pole is

beginning to point away from the sun, the Northern Hemisphere experiences fall.

D. Winter

This answer is not correct. When the North Pole point away from the sun, the sun’s rays

strike the Northern Hemisphere less directly. When the sunlight is less direct, the region

experiences the winter season.


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Question 24


Benchmark: SC.8.8.4 Explain how the sun is the major source of energy influencing climate and weather on Earth. Answer Key: B

The diagram shows a sea breeze. A sea breeze blows from the sea toward the land.

What is the role of the sun in creating a sea breeze? A. The sun warms the land, creating a condition of higher air pressure that pulls in the cooler

sea air.

This answer is not correct. When the air above the land is warmed, its density decreases. Therefore, its air pressure becomes lower, not higher.

B. The sun warms the land faster than the sea, causing the air above the land to expand and rise. This answer is correct. Because the land surface warms faster than the ocean surface, the air above the land becomes warmer and less dense, and it rises. This creates an area of low pressure that draws the cooler sea air inland.

C. The sun warms the sea, creating waves that move the air above the sea surface toward the land. This answer is not correct. While solar energy is indirectly involved in the formation of the ocean’s surface waves, these waves are caused by the wind, not the other way around.

D. The sun warms the sea faster than the land, causing the air above the sea to expand and spread out.

This answer is not correct. While it is true that heated air will expand, solar energy warms the land surface faster than the ocean surface.


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Question 25


Benchmark: SC.8.8.10 Compare the characteristics and movement patterns of the planets in

our solar system

Answer Key: C

Which of the following best describes the inner planets of the solar system?

A. Large gas planets with thick atmospheres

This answer is not correct. This would be a good description for the outer planets, not the

inner planets.

B. Small planets of ice with elliptical orbits

This answer is not correct. All planets have elliptical orbits, but only the dwarf outer planets

are made up largely of ice.

C. Dense, rocky planets with few moons

This answer is correct. The four inner planets are known as the terrestrial planets because

they have solid surfaces and are made from dense minerals and rocks. The inner planets

have fewer moons compared to the outer planets.

D. Barren planets with rings of gas and dust

This answer is not correct. Some of the outer planets have rings of gas and dust, but none of

the inner planets have rings.


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Question 26


Benchmark: SC.8.8.6 Explain the relationship between density and convection currents in the ocean and atmosphere. Answer Key: D

The list shows the procedure that a student used to perform an experiment.

Fill a large container with ice water.

Fill a small, open jar with warm water and add two drops of blue food coloring.

Lower the small jar to the bottom of the large container of ice water.

Observe and document what happens. What phenomenon was this student investigating?

A. Changes in water temperature

This answer is not correct. The procedure did not include the use of a thermometer to measure water temperatures.

B. Changes in water pressure

This answer is not correct. The procedure did not include the use of a water pressure gauge to measure water pressure.

C. Conduction between the two jars

This answer is not correct. While conduction occurs between the warm and cold water and between the two jars where they touch, the procedure does not include instruction on how to measure conduction.

D. Convection currents in the water

This answer is correct. Introducing the dyed, warm water into the cold water provides the conditions necessary for convection to occur: two masses of water with different densities due to their different temperatures.


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Question 27


Benchmark: SC.8.8.7 Describe the physical characteristics of oceans

Answer Key: D

The illustration shows how deep ocean water is brought to the surface in a process called upwelling.

Which factor is directly responsible for upwelling?

A. Sunlight

This answer is not correct. Energy from the sun is responsible for warming the surface water, not deep ocean water. The deep ocean water is cold relative to the surface water. Temperature alone does not contribute to upwelling since cold water sinks and warm water rises.

B. Tide

This answer is not correct. While the tides cause all water in the ocean to rise and fall, they do not bring deep ocean water up from the bottom.

C. Waves

This answer is not correct. Ocean waves only move water close to the surface; they do not affect deep ocean water.

D. Wind

This answer is correct. Surface winds cause surface ocean currents to move away from

the shore. Upwelling occurs when the water that is forced out to sea is replaced by water

rising up from the bottom.


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Question 28


Benchmark: SC.8.8.7 Describe the physical characteristics of oceans Answer Key: B

The average salinity of ocean water is about 35 parts per thousand.

How does an increase in evaporation of ocean water affect salinity at the ocean surface?

A. Ocean salinity decreases.

This answer is not correct. As the water evaporates, the salt remains. Therefore, salinity will increase, not decrease.

B. Ocean salinity increases.

This answer is correct. The salinity will increase because, as the amount of water decreases, the amount of salt remains constant.

C. Ocean salinity remains the same.

This answer is not correct. The salinity will increase if evaporation increases.

D. Ocean salinity varies in a cyclical pattern.

This answer is not correct. Although ocean salinity varies from location to location, an

increase in evaporation would cause an overall increase in salinity.


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Question 29


Benchmark: SC.8.8.9 Explain the predictable motions of the Earth and moon

Answer Key: D

A student wants to model an Earth year using a ball, a rod, a string, and a light source.

Which model accurately represents one Earth year?

A.

Push a rod through the center of the ball. Tilt the ball. Spin the ball one time.

This answer is not correct. This model shows how the length of a day is determined by Earth completing one rotation.

B.

Push a rod through the center of the ball. Tilt the ball. Shine a flashlight on one side of the ball (1) and then on the opposite side (2).

This answer is not correct. This model shows how the seasons are determined by Earth’s revolution and axis tilt.


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C.

Push a rod through the center of the ball. Tilt the ball. Shine a flashlight on the ball. Walk around the ball one time while shining the light on it.

This answer is not correct. This model shows the sun orbiting Earth.

D.

Push a rod through the center of the ball. Tilt the ball. Turn on the light. Hold the ball while walking around the light one time.

This answer is correct. This model represents one revolution of Earth around the sun. The time it takes to complete one orbit is the length of a year.


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Question 30


Benchmark: SC.8.8.12 Describe the role of gravitational force in the motions of planetary systems Answer Key: C

The table lists the distances between Mars and the sun at four different times of the Martian year.

When is the gravitational force between Mars and the sun the strongest?

A. Summer solstice

This answer is not correct. During the summer solstice, Mars is farthest from the sun, so the force of gravity between the two bodies is weakest.

B. Fall equinox

This answer is not correct. During the fall equinox, Mars is not at its closest point to the sun, so the force of gravity between the two bodies is not strongest.

C. Winter solstice

This answer is correct. The force of gravity is affected by the mass of the two objects and the distance between them. Since the mass of both the sun and Mars is not changing, the distance is the factor that will determine the force of gravity between them. During the winter solstice, Mars is closest to the sun, so the force of gravity between the two bodies is strongest.

D. Spring equinox

This answer is not correct. During the spring equinox, Mars is not at its closest point to the

sun, so the force of gravity between the two bodies is not strongest.

Grade 8 Science Practice Test Answer Key Question 1 ... · Grade 8 Science Practice Test Answer Key...

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