Chapter 7H

The element oxygen, represented by the symbol O, is classified as

• a pure substance
• a compound
• a mixture
• a solution

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The chemical combination of two or more different kinds of atoms in fixed amounts is called a(n)

• orbit
• compound
• mixture
• element

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Carbon dioxide is formed when two oxygen atoms chemically combine with a carbon atom. Which term best describes carbon dioxide?

• atom
• mixture
• element
• compound

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Carbon (C) and hydrogen (H) are pure substances. Each is made of only one type of atom, but carbon atoms are different from hydrogen atoms. Carbon and hydrogen chemically combine to form methane (CH4).

• methane is an element and carbon and hydrogen are compounds.
• carbon, hydrogen, and methane are all elements.
• carbon, hydrogen, and methane are all compounds.
• carbon and hydrogen are elements and methane is a compound.

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What defines a mixture?

• described by a chemical formula
• can be broken down into its basic substances through physical means
• created through a chemical reaction
• cannot be broken down into simpler substances

The air we breathe contains different individual gases (mostly nitrogen and oxygen). Which of the following correctly describes the air we breathe?

• compound
• liquid
• element
• mixture

This is the smallest unit of an element.

• atom

• molecule

• compound

• nucleus

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This is any combination of two or more atoms from different elements that are chemically combined.

• compound

• molecule

• element

• pure substance

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This is what holds atoms in a molecule and compound together. They can be ionic, covalent, or metallic (and you'll learn about these in high school chemistry).

• chemical bond

• chemical formula

• chemical symbol

• electron cloud

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This is a one or two letter representation of each element that is generally close to the element's name. The first letter of this will ALWAYS be capitalized.

• chemical symbol

• chemical number

• atomic number

• atomic mass