Grade 8 Science - EOY Practice test #1

Janice is learning about compounds. Which of the following best describes a compound?

• a substance made up purely of one element

• a group of substances that are either acids or bases

• a group of substances that can be separated by a physical change

• a substance made up of two or more elements that are chemically combined

Answer explanation

A compound is defined as a substance made up of two or more elements that are chemically combined. This distinguishes it from elements, mixtures, and substances that can be separated by physical changes.

Scientific theories are developed over time in all areas of science. Which statement best describes scientific theories?

• They are based on scientific laws that came first.

• They are pieces of scientific evidence that support a hypothesis.

• They are explanations of scientific events that may change based on continuous research.

• They are predictions of events that usually remain constant because scientific ideas rarely change.

Answer explanation

Scientific theories are dynamic explanations of scientific events that evolve with ongoing research, making the correct choice the one that acknowledges their potential to change.

Many interactions occur between the biosphere and the atmosphere. One of these interactions results in changes in atmospheric carbon dioxide (CO2) levels. The graph above shows these changes over a two‑year period. Which of the following changes in the biosphere most likely caused these changes in the atmospheric CO2 levels?

• Streams froze in the winter and melted in the spring.

• Plants grew leaves in the spring and lost leaves in the fall.

• Offspring were born in the summer and matured in the fall.

• Soil dried out in the summer and absorbed moisture in the winter.

Answer explanation

The increase in atmospheric CO2 levels corresponds with plant growth in spring, as leaves absorb CO2 for photosynthesis. In fall, leaf loss releases CO2, causing the observed fluctuations in atmospheric levels.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-1

NGSS.MS-LS2-3

NGSS.MS-LS2-4

Jordan adds some soil and plants to a large glass jar to build a terrarium. He waters the plants and then adds two snails, two crickets, and an earthworm to the jar. Jordan then places the lid tightly on the jar and sets it on a sunny windowsill. Based on the law of conservation of mass, which of the following is expected to occur inside Jordan’s terrarium?

• The mass will increase as the plants grow and decrease when the snails eat the plants.

• The mass will increase as the earthworm digests the soil.

• The mass will decrease when the crickets die.

• The mass will neither increase nor decrease.

Answer explanation

According to the law of conservation of mass, the total mass in a closed system remains constant. In Jordan's terrarium, no matter the changes in living organisms, the overall mass will neither increase nor decrease.

Tags

NGSS.MS-PS1-5

Human body systems interact to keep blood pressure within a normal range. The diagram represents this interaction. Which of the following best describes what is occurring in part X of the diagram?

• A) Respiration remains high as other body systems work with the circulatory system.

• B) Blood pressure is regulated as the circulatory system shuts down other body systems.

• C) Blood pressure remains high as the circulatory system shuts down other body systems.

• D) Homeostasis is maintained as the other body systems work with the circulatory system.

Answer explanation

Part X illustrates how various body systems collaborate to maintain homeostasis, ensuring blood pressure stays within a normal range. This aligns with choice D, as it emphasizes the cooperative function of systems rather than shutting them down.

Tags

NGSS.MS-LS1-3

The table shows the range of frequencies, in Hertz (Hz), for part of the electromagnetic spectrum.

Which of the following types of radiation has the longest wavelength?

• A. Infrared

• B. Ultraviolet

• C. X-rays

• D. Gamma rays

Answer explanation

Infrared radiation has the longest wavelength in the electromagnetic spectrum compared to ultraviolet, X-rays, and gamma rays, which have progressively shorter wavelengths.

Tags

NGSS.MS-PS4-2

An astronomer observes a sunspot. Which of the following describes this feature of the Sun?

• a location where heat rises to the Sun’s surface

• a location that produces most of the Sun’s heat energy

• a location that is cooler than other parts of the Sun’s surface

• a location where energy and matter leave the Sun’s atmosphere

Answer explanation

A sunspot is a region on the Sun's surface that is cooler than its surrounding areas, due to magnetic activity inhibiting heat flow. This makes the correct choice 'a location that is cooler than other parts of the Sun’s surface'.

Ricky wants to finish constructing a chart that helps classify two organisms. The chart is shown here.

Accurately answering which question would best help distinguish these organisms as members of the animal kingdom rather than the plant or fungi kingdom?

• 1

• 2

• 3

• 4

Answer explanation

Question 3 likely addresses key characteristics of animals, such as mobility or heterotrophy, which are distinct from plants and fungi. This helps classify the organisms as members of the animal kingdom.

Tags

NGSS.MS-LS1-1

Atoms are made up of subatomic particles, including neutrons. Which of the following describes a neutron?

• has a greater volume than the electron cloud

• has more mass than the nucleus

• has no charge

• has no mass

Answer explanation

A neutron is a subatomic particle found in the nucleus of an atom and is electrically neutral, meaning it has no charge. This distinguishes it from protons, which are positively charged, and electrons, which are negatively charged.

Two groups of students hypothesized that rocks on Earth’s surface are damaged by acid rain.

● Group X tested the hypothesis by examining the properties of some rocks and pouring a weak acid, vinegar, on each of the rocks.

● Group Y later repeated the same procedure with a different group of rocks.

The rocks used for the investigations and the results from each student group are shown below.

Which of the following best describes an advantage Group X has over Group Y in supporting the hypothesis?

• A. Group X tested the rocks before Group Y did.

• B. Group X tested more rocks that are smoother.

• C. Group X tested rocks with a greater average mass.

• D. Group X tested a greater variety of rocks than Group Y did.

Answer explanation

Group X's advantage lies in testing a greater variety of rocks, which provides a more comprehensive understanding of how different rock types react to acid rain, strengthening their support for the hypothesis.

Tags

NGSS.MS-PS1-2