Elements, compounds, and mixtures. A student performs three experiments. In the first experiment, the student combines iron filings and sulfur powder in a dish. The student holds a magnet over the dish and observes that the iron filings are attracted to the magnet. The student's set up and observation are shown. In the second experiment, the student combines iron filings and sulfur powder in a test tube. The iron filings and sulfur powder are heated until iron sulfide is formed. After cooling, the student holds the magnet over the test tube. The magnet does not attract the iron filings. The set up and observation are shown. In the third experiment, the student uses two beakers of water. To one beaker, a tablespoon of sugar is added and stirred. The resulting solution is uniform throughout. To the other beaker, a tablespoon of oil is added and stirred. The resulting solution does not have a uniform composition. Both beakers are shown before and after. Which statement best describes the iron sulfide that forms in Experiment 2?

It is a compound formed through a chemical reaction.

It is an element formed through a chemical reaction.

It is a homogeneous mixture formed through a physical change.

It is a heterogenous mixture formed through a physical change.

Elements, compounds, and mixtures. A student performs three experiments. In the first experiment, the student combines iron filings and sulfur powder in a dish. The student holds a magnet over the dish and observes that the iron filings are attracted to the magnet. The student's set up and observation are shown. In the second experiment, the student combines iron filings and sulfur powder in a test tube. The iron filings and sulfur powder are heated until iron sulfide is formed. After cooling, the student holds the magnet over the test tube. The magnet does not attract the iron filings. The set up and observation are shown. In the third experiment, the student uses two beakers of water. To one beaker, a tablespoon of sugar is added and stirred. The resulting solution is uniform throughout. To the other beaker, a tablespoon of oil is added and stirred. The resulting solution does not have a uniform composition. Both beakers are shown before and after. Which statement best supports that iron sulfide is a compound formed through a chemical reaction.

Iron sulfide has different properties than iron and sulfur and cannot be separated through physical means.

Iron sulfide has the same properties as iron and sulfur and can be easily separated.

Iron sulfide has the same composition as iron and sulfur and can be easily separated.

Iron sulfide has a different temperature than iron and sulfur and cannot be separated through physical means.

What statement is true about the eight elements on the periodic table termed metalloids?

They have properties of both metals and nonmetals.

They are the only man-made elements.

They all have the same number of protons and neutrons.

They are the only naturally occurring elements.

The periodic table is organized into vertical groups of

elements with similar properties.

compounds with different properties.

elements with different properties.

compounds with similar properties.

Which of following explains the location of oxygen on the periodic table?

It has one more proton than nitrogen, so it is located after nitrogen, and it is a non-metal, so it located on the right side of the periodic table.

It has one more proton than nitrogen, so it is located after nitrogen, and it is a metal, so it is located on the right side of the periodic table.

It has one less proton than nitrogen, so it is located after nitrogen, and it is a non-metal, so it is located on the right side of the periodic table.

It has one less proton than nitrogen, so it is located after nitrogen, and it is a metal, so it is located on the right side of the periodic table.

When sodium is mixed with water, an explosion takes place. Based on its location on the periodic table, how will potassium behave with water?

Potassium, which shares similar properties with sodium, will explode in water.

Potassium, which shares similar properties with sodium, will not explode in water.

Potassium, which does not share similar properties with sodium, will explode in water.

Potassium, which does not share similar properties with sodium, will not explode in water.

Burning Steel Wool Investigation Jamie and Alexa are investigating physical and chemical reactions in a science class. They perform the experiment described in the steps below as part of their investigation. Materials: – Fine steel wool – 9-volt battery – Aluminum pan Procedure Steps: 1. Take a small piece of steel wool and form it into a loose ball. 2. Place the steel wool in the aluminum pan. 3. Lightly touch the positive and negative terminals on the battery to the steel wool. 4. Gently blow on the steel wool to get the reaction to occur more quickly. The battery in the investigation provides an electrical current that heats up the steel wool, allowing it to burn. The equation for the reaction of steel wool burning is: 4Fe(s) + 3O 2 (g) → 2Fe 2 O 3 (s) The table shown below provides information about the steel wool and the iron oxide formed from burning the steel wool. How can the melting point and boiling point of oxygen BEST be compared to the melting points and boiling points for steel wool and iron oxide?

Oxygen will have different melting and boiling points than steel wool and iron oxide since they all have their own properties.

Oxygen will have the same melting and boiling points as iron oxide as this product also contains oxygen.

Oxygen will have the same melting and boiling points as steel wool since they are both reactants.

Oxygen will have different melting and boiling points than steel wool and iron oxide since they are all a part of a physical reaction.

Zinc and Hydrochloric Acid A teacher wearing a lab coat and safety goggles conducts an experiment under a vent hood in a chemistry laboratory. The students observe and take notes. In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form, and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place. After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable. Which statement BEST interprets the temperature change that occurred in the experiment?

When the substances were combined, the chemical reaction released heat.

Reactions that include zinc discs release heat.

Reactions that include hydrochloric acid release heat.

When the substances were combined, the physical change released heat.

Zinc and Hydrochloric Acid A teacher wearing a lab coat and safety goggles conducts an experiment under a vent hood in a chemistry laboratory. The students observe and take notes. In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form, and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place. After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable. Did a chemical reaction take place? Explain why or why not.

Yes, because the reactants were not flammable, but the gaseous product was flammable

No, because neither the reactants nor the liquid product were flammable

No, because the mass in the flask appears to change when the reaction takes place

Yes, because the mass in the flask appears to be the same both before and after the reaction took place

Zinc and Hydrochloric Acid A teacher wearing a lab coat and safety goggles conducts an experiment under a vent hood in a chemistry laboratory. The students observe and take notes. In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form, and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place. After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable. Which statement BEST explains why the gas in the balloon was flammable, but the reactants were not?

The atoms of the reactants were rearranged into a new substance with new chemical properties.

Atoms were created when the reaction took place, which resulted in the appearance of a flame.

Atoms were destroyed when the reaction took place, which resulted in the appearance of a flame.

The atoms of the reactants were rearranged into a new substance with new physical properties.

The students in Ms. Ramirez's science class are classifying different types of reactions. They have divided the reactions into two columns, as shown below. Why are the reactions listed in Column B classified as physical reactions?

The materials maintained their original properties.

They produced new substances with different properties.

They released heat during the reactions.

The reactions are irreversible.

The students in Ms. Ramirez's science class are classifying different types of reactions. They have divided the reactions into two columns, as shown below. Why are the reactions listed in Column A classified as chemical reactions?

They changed the properties of the materials irreversibly.

The changes do not affect the materials' characteristics.

The changes to the materials can be easily reversed.

They changed the shape of the materials.

Read the passage about mass in a combustion reaction. The combustion of methane is a reaction in which methane gas burns in oxygen to produce carbon dioxide and water vapor. It is represented by the equation: CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (g) In the equation, one molecule of methane gas requires two molecules of oxygen gas to produce one molecule of carbon dioxide gas and two molecules of water in vapor form. The molecules in the equation can be modeled with circles to represent atoms and straight lines to represent the bonds between them, as shown in the picture. What evidence supports the claim that the combustion of methane shown in the equation is a chemical change?

The atoms on the right side of the equation are organized into different molecules compared to the molecules on the left side of the equation.

The numbers of atoms present on the left and right sides of the equation are equal.

The atoms of the reactants and products in the equation are present in the same phase.

The mass of the atoms on the left side of the equation is equal to the mass of the atoms on the right side of the equation.

The diagram shows a test tube of copper (II) sulfate solution before and after the addition of iron shavings during an experiment. The experiment shows a

chemical reaction, because the solution unexpectedly changed color.

physical reaction, because it involved a compound.

physical reaction, because the solution changed color.

chemical reaction, because it involved a mixture.

Water Formation Water (H 2 O) is a compound required for survival by living organisms. The diagram below shows the chemical reaction of hydrogen gas (H 2 ) with oxygen gas (O 2 ) to form water (H 2 O). Choose the statement that BEST compares the mass of the products to the mass of the reactants.

The number of hydrogen atoms and oxygen atoms is the same before and after the reaction, so the mass does not change during the reaction.

The number of hydrogen atoms and oxygen atoms changes during the reaction, so the mass changes during the reaction.

The number of hydrogen atoms and oxygen atoms changes during the reaction, but the mass does not change during the reaction.

The number of hydrogen atoms and oxygen atoms is the same before and after the reaction, but the mass changes during the reaction.

The combustion of methane is a reaction in which methane gas burns in oxygen to produce carbon dioxide and water vapor. It is represented by the equation: CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (g) In the equation, one molecule of methane gas requires two molecules of oxygen gas to produce one molecule of carbon dioxide gas and two molecules of water in vapor form. The molecules in the equation can be modeled with circles to represent atoms and straight lines to represent the bonds between them, as shown in the picture. A student observes the model and claims that the total mass of the reaction is conserved. Is the student's claim correct? Why or why not?

Yes, because the number of atoms of each element is the same on both sides of the equation.

No, because the arrangement of atoms is different in the reactants and products.

Yes, because the reactants and products are made of atoms of the same elements.

No, because the total number of atoms in products is greater than the total number of atoms in reactants.

A stack of newspapers is burned completely to ash in a laboratory. How does the resulting mass relate to the initial mass of the stack of newspapers?

The mass of the gases and the ash should equal the mass of the initial stack of newspapers.

The mass of the gases and the ash should be one-fourth the mass of the initial stack of newspapers.

The mass of the gases and the ash should be one-half the mass of the initial stack of newspapers.

The mass of the gases and the ash should be double the mass of the initial stack of newspapers.

A chemical reaction is shown. Zn(OH) 2 + NaOH → Na 2 ZnO 2 + H 2 O Which choice shows a balanced chemical reaction that supports the law of conservation of matter?

Zn(OH) 2 + 2NaOH → Na 2 ZnO 2 + 2H 2 O

Zn(OH) 2 + 2NaOH → 2Na 2 ZnO 2 + 2H 2 O

2Zn(OH) 2 + 2NaOH → Na 2 ZnO 2 + 4H 2 O

2Zn(OH) 2 + 2NaOH → Na 2 ZnO 2 + 2H 2 O

Chemistry Unit Test - 2025

Authored by Shirley Martin

Science

8th Grade

NGSS covered

Used 4+ times

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40 questions

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DROPDOWN QUESTION

1 min • 1 pt

A student develops a model of methane (CH₄), as shown. Use the drop-down menus to identify the substance in the model as an element or a compound. The model is a(n) (a) because it shows (b) one type of atom and is (c) by a chemical bond.

compound

element

more than

only

held together

not held together

Tags

NGSS.MS-PS1-1

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

The picture shows an isotope of an element. Based on the information in the periodic table, which element is shown in the picture?

boron (B)

lithium (Li)

carbon (C)

helium (He)

Tags

NGSS.MS-PS1-1

MULTIPLE SELECT QUESTION

45 sec • 1 pt

Liam explores the decomposition of water. He attaches a battery to the ends of two pencils sharpened at both ends, and places the other ends of the pencils in a beaker of water. His set up is shown below.
Liam knows that some of the bubbles in his experiment must be oxygen. He draws an atomic model of the element oxygen. What does he include in his drawing? Select all that apply.

eight protons in the nucleus

sixteen protons in the nucleus

eight electrons outside of the nucleus

sixteen electrons outside of the nucleus

eight neutrons in the nucleus

Tags

NGSS.MS-PS1-1

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Darnell draws a picture of a nitrogen atom. He draws a small circle to represent the nucleus and draws dots around the circle to represent the electrons. How many dots does he draw?

5 dots

7 dots

14 dots

16 dots

Tags

NGSS.MS-PS1-1

MULTIPLE SELECT QUESTION

45 sec • 1 pt

Bernice draws an oxygen atom. She draws a small circle for the nucleus. Inside of the circle, she draws plus signs for protons and dots for neutrons. Around the nucleus she uses minus signs to represent electrons. Which statements are true about her drawing? Select ALL that apply.

There are eight protons in the nucleus.

There are sixteen protons in the nucleus.

There are eight neutrons in the nucleus.

There are sixteen neutrons in the nucleus.

There are sixteen electrons in her drawing.

Tags

NGSS.MS-PS1-1

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Using information from the periodic table, which diagram shows a correct model for an atom of neon?

Tags

NGSS.MS-PS1-1

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Pure Substances and Mixtures
Two categories of substances are pure substances and mixtures.
Pure substances have a constant chemical composition and chemical properties. Elements and compounds are examples of pure substances. Elements consist of one or more of one type of atom and are not chemically bonded. Compounds consist of two or more types of elements that are held together with a chemical bond.
Mixtures contain two or more different substances that are not held together with a chemical bond. Two types of mixtures are homogeneous and heterogeneous mixtures. Homogeneous mixtures have a uniform composition throughout the mixture, while heterogenous mixtures do not.
A student develops models of pure substances and mixtures using different colors of balls and plastic sticks. A key for each element and chemical bond is shown.
A model of a substance in a container is shown. Which best identifies the type of substance in the container?

element

compound

heterogeneous mixture

homogeneous mixture

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NGSS.MS-PS1-1

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Chemistry Unit Test - 2025

A student develops a model of methane (CH4), as shown. Use the drop-down menus to identify the substance in the model as an element or a compound. The model is a(n)​ (a) because it shows​ (b) one type of atom and is​ (c) by a chemical bond.

The picture shows an isotope of an element. Based on the information in the periodic table, which element is shown in the picture?

Darnell draws a picture of a nitrogen atom. He draws a small circle to represent the nucleus and draws dots around the circle to represent the electrons. How many dots does he draw?

Bernice draws an oxygen atom. She draws a small circle for the nucleus. Inside of the circle, she draws plus signs for protons and dots for neutrons. Around the nucleus she uses minus signs to represent electrons. Which statements are true about her drawing? Select ALL that apply.

Using information from the periodic table, which diagram shows a correct model for an atom of neon?

​ ​ Which 2 are pure substances?

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A student develops a model of methane (CH₄), as shown. Use the drop-down menus to identify the substance in the model as an element or a compound. The model is a(n) (a) because it shows (b) one type of atom and is (c) by a chemical bond.

Which 2 are pure substances?