Grade 8 Science Sample Items

Ethan is observing the chemical and physical properties of a substance. He heats a substance and observes that the substance changes from a brown solid to a black powder. He refers to several chemistry journals that state this represents a chemical reaction. From his observation and research, he concludes that the substance undergoes a chemical change when heated. How can Ethan best defend his conclusion?

• by demonstrating that the substance will eventually melt if the temperature continues to increase

• by verifying that the substance is now composed of different molecules than it was before being heated

• by verifying that the substance is composed of only one type of element

• by demonstrating that the substance is less dense after being heated

Answer explanation

Ethan can best defend his conclusion by verifying that the substance is now composed of different molecules than it was before being heated, indicating a chemical change has occurred.

Tags

NGSS.MS-PS1-2

Mr. Roberts drives his car away from his house at a constant speed. Which of the following graphs best shows the relationship between the distance traveled and the driving time?

• A. (Graph showing a horizontal line: Distance vs. Time)

• B. (Graph showing a straight line with positive slope: Distance vs. Time)

• C. (Graph showing a vertical line: Distance vs. Time)

• D. (Graph showing a straight line with negative slope: Distance vs. Time)

Answer explanation

Mr. Roberts drives at a constant speed, meaning distance increases steadily over time. This relationship is best represented by a straight line with a positive slope, indicating that as time increases, distance also increases. Thus, the correct choice is B.

At what point in the cycle shown above would the process of rock decomposition occur?

• A. J

• B. K

• C. L

• D. M

Answer explanation

Rock decomposition occurs at point J, where weathering processes begin to break down rocks into smaller particles, making it the correct choice for this stage in the cycle.

An object moves through space with balanced forces acting on it. Which statement best describes the speed and direction of the object while the forces acting on it remain balanced?

• The speed and direction of the object will both change.

• The speed and direction of the object will remain constant.

• The speed will change, but the direction will remain constant.

• The speed will remain constant, but the direction will change.

Answer explanation

When balanced forces act on an object, it remains in a state of equilibrium. This means that both the speed and direction of the object will remain constant, as there is no net force to change its motion.

A scientist conducts an experiment and asks other scientists around the world to replicate it. Why would other scientists attempt to perform the same experiment?

• to find out if the climate of various regions of the world would affect the results

• to see if the experiment would be less costly in another part of the world

• to confirm the results of the experiment conducted by the scientist

• to verify that the hypothesis of the experiment is a scientific law

Answer explanation

Other scientists attempt to replicate the experiment to confirm the results of the original study. Replication is essential in science to ensure findings are reliable and not due to chance or experimental error.

Tags

NGSS.MS-LS2-4

Mrs. Alvarez's eighth-grade science class is investigating how temperature, in degrees Celsius (°C), affects the solubility of a compound in 100 milliliters (mL) of water. Mrs. Alvarez provides the students with a graph indicating the solubility of a certain compound, in grams (g), as shown below. She then tells the students that she will demonstrate how many grams of the compound will dissolve in 100 mL of water at 40°C. How many grams of the compound will dissolve in 100 mL of water at 40°C?

• 80 grams

• 40 grams

• 100 grams

• 60 grams

Answer explanation

At 40°C, the graph indicates that 80 grams of the compound will dissolve in 100 mL of water. Therefore, the correct answer is 80 grams.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Mrs. Alvarez's eighth-grade science class is investigating how temperature, in degrees Celsius (°C), affects the solubility of a compound in 100 milliliters (mL) of water. Mrs. Alvarez provides the students with a graph indicating the solubility of a certain compound, in grams (g), as shown below. According to the graph, at what temperature does the compound have the greatest solubility?

• 10°C

• 30°C

• 50°C

• 60°C

Answer explanation

According to the graph, the solubility of the compound increases with temperature, reaching its peak at 60°C, where it has the greatest solubility compared to the other temperatures listed.

Tags

NGSS.MS-PS1-2

Based on the information from the graph, which of the following is the best prediction of how many grams of the compound will dissolve at 40°C?

• 40 g

• 65 g

• 85 g

• 100 g

Answer explanation

The graph indicates that at 40°C, the solubility of the compound is approximately 65 grams. This is the closest value to the data shown, making 65 g the best prediction for how much will dissolve at this temperature.

Food webs show the feeding relationships between different types of organisms. These organisms have a specific niche. Which of the following best describes a function of decomposers in food webs?

• recycle nutrients in the soil

• convert solar energy into food

• provide food for secondary consumers

• compete with secondary consumers for oxygen

Answer explanation

Decomposers play a crucial role in food webs by breaking down dead organic matter, which recycles nutrients back into the soil, enriching it for plants. This process is essential for maintaining ecosystem health.

Tags

NGSS.MS-LS2-3

The interaction between the cryosphere and the hydrosphere can have an impact on Earth's oceans. Which of the following is an example of an interaction between the cryosphere and the hydrosphere?

• evaporation of water from the oceans at the equator

• release of fresh water into ocean water when icebergs melt

• decomposition of organic matter at the bottom of the oceans

• release of large amounts of salt from icebergs into the ocean

Answer explanation

The correct choice, 'release of fresh water into ocean water when icebergs melt', illustrates the interaction between the cryosphere (ice) and the hydrosphere (ocean water), affecting ocean salinity and circulation.