8th grade science Practice Test

Ethan is observing chemical and physical properties of a substance. He heats a substance and observes that the substance turns from a brown solid to a black powder. He refers to several chemistry journals that claim this represents a chemical reaction. From his observation and research, he concludes that the substance goes through 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 made up of different molecules than before it was heated

• . by verifying that the substance is made up of only one type of element

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

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 time spent driving?

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Ice forms in the cracks of a basalt rock formation and breaks some rock into smaller pieces. The diagram below shows part of the rock cycle.

At which point in the cycle shown above would the process of breaking down rocks occur?

• J

• K

• L

• M

Students in Ms. Alvarez’s eighth grade science class are investigating how temperature, in degrees Celsius (˚C), affects the solubility of a compound in 100 milliliters (mL) of water. Ms. Alvarez provides the students with a graph that shows the solubility of a certain compound, as shown here.

She then tells the students that she will demonstrate how many grams (g) of the compound will dissolve in 100 mL of water at 40˚C. Based on the information in the graph, which of the following is the best prediction of how many grams of the compound will dissolve at 40˚C?

• 40g

• 65g

• 85g

• 100g

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

A scientist performs an experiment and asks other scientists around the world to replicate it. Why would other scientists most likely try to perform the same experiment?

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

• to see if the experiment would be less expensive 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

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

• to recycle nutrients into soil

• to convert solar energy into food

• to provide food for secondary consumers

• to compete with secondary consumers for oxygen

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

• evaporation of water from oceans at the equator

• release of fresh water into ocean water as icebergs melt

• decomposition of organic matter at the bottom of oceans

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

Several factors can cause weather patterns in the atmosphere. The diagram below shows how air movement near the equator can form thunderstorms.

Which process is the main source of this movement?

• movement of ocean currents

• decrease in relative humidity

• heating by energy from the Sun

• warming in the upper atmosphere

Based on information from the graph, which of the following best compares the physical properties of two of the substances?

• Substance X has less mass than substance Y has

• Substance W has less volume than substance X has.

• Substance Y would have less mass than substance Z would have if they had the same volume

• Substance Z would have less mass than substance W would have if they had the same volume.