Elements vs. Compounds Quiz

Which of the following is an element?

• Water

• Oxygen

• Salt

• Sugar

Answer explanation

Oxygen is an element, represented by the symbol O on the periodic table. In contrast, water (H2O), salt (NaCl), and sugar (C12H22O11) are compounds made up of multiple elements.

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DOK Level 1: Recall

What is the smallest unit of a compound that retains its chemical properties?

• Atom

• Molecule

• Electron

• Proton

Answer explanation

The smallest unit of a compound that retains its chemical properties is a molecule. Molecules are formed when two or more atoms bond together, while atoms alone do not represent a compound.

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DOK Level 1: Recall

Which of the following statements is true about elements and compounds?

• Elements can be broken down into simpler substances by chemical means.

• Compounds are made of two or more elements chemically combined.

• Compounds consist of only one type of atom.

• Elements are made of two or more compounds.

Answer explanation

The correct statement is that compounds are made of two or more elements chemically combined. Elements cannot be broken down by chemical means, consist of one type of atom, and are not made of compounds.

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DOK Level 2: Skill/Concept

Identify the compound from the following list:

• Helium

• Carbon Dioxide

• Gold

• Nitrogen

Answer explanation

Carbon Dioxide is a compound made of two different elements: carbon and oxygen. In contrast, helium and gold are elements, while nitrogen is a diatomic molecule, not a compound.

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DOK Level 1: Recall

Which of the following best describes the difference between an element and a compound?

• Elements are always gases, while compounds are always solids.

• Elements are pure substances made of one type of atom, while compounds are made of two or more types of atoms chemically bonded.

• Elements can be separated into simpler substances, while compounds cannot.

• Compounds are pure substances made of one type of atom, while elements are made of two or more types of atoms chemically bonded.

Answer explanation

The correct choice states that elements are pure substances made of one type of atom, while compounds consist of two or more types of atoms chemically bonded. This accurately reflects the fundamental difference between elements and compounds.

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DOK Level 2: Skill/Concept

• An element

• A compound

• A mixture

• A solution

Answer explanation

The formula H2O represents a compound, specifically water, which is made up of two hydrogen atoms and one oxygen atom chemically bonded together. It is not an element, mixture, or solution.

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DOK Level 1: Recall

• It is made of only one type of atom.

• It is a mixture of hydrogen and oxygen gases.

• It is made of two different elements chemically bonded together.

• It can be separated into hydrogen and oxygen by physical means.

Answer explanation

Water (H2O) is a compound because it consists of two different elements, hydrogen and oxygen, that are chemically bonded together. This distinguishes it from mixtures, which do not involve such bonds.

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DOK Level 2: Skill/Concept

If you have a sample of pure iron and a sample of rust (iron oxide), how would you classify each?

• Both are elements.

• Both are compounds.

• Iron is an element, and rust is a compound.

• Iron is a compound, and rust is an element.

Answer explanation

Iron is a pure substance made of only one type of atom, classifying it as an element. Rust, or iron oxide, is formed when iron reacts with oxygen, making it a compound composed of different elements.

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DOK Level 2: Skill/Concept

A student claims that salt (NaCl) is an element because it is a pure substance. Evaluate this claim.

• The claim is correct because salt is a pure substance.

• The claim is incorrect because salt is a compound made of sodium and chlorine.

• The claim is correct because salt cannot be broken down into simpler substances.

• The claim is incorrect because salt is a mixture of sodium and chlorine.

Answer explanation

The claim is incorrect because salt (NaCl) is a compound formed from sodium and chlorine atoms. While it is a pure substance, it is not an element, as elements cannot be broken down into simpler substances.

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DOK Level 3: Strategic Thinking

• It is made of only one type of atom.

• It is a mixture of carbon and oxygen gases.

• It is made of two different elements chemically bonded together.

• It can be separated into carbon and oxygen by physical means.

Answer explanation

Carbon dioxide (CO2) is classified as a compound because it consists of two different elements, carbon and oxygen, that are chemically bonded together. This distinguishes it from elements, which are made of only one type of atom.

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DOK Level 3: Strategic Thinking