Molecules are held together by forces called

• physical bonds

• chemical bonds

Carbon and oxygen combine chemically to form carbon dioxide. Carbon dioxide is

• an ion

• a nucleus

• a compound

• an atom

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NGSS.MS-PS1-5

A compound can be separated chemically into

• elements

• molecules

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2 atoms of hydrogen and 1 atom of oxygen combine to form water. What is the chemical formula for water?

• H₂O

• H₂O₂

• HO₂

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NGSS.MS-PS1-1

Carbon dioxide's chemical formula is known as

• C₂O₂

• CO

• CO₂

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Subscripts are used to identify the number of atoms in a compound. How many atoms of carbon are in C₆H₈O₆? (Better known as Vitamin C.)

• 8

• 6

• 12

• 20

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NGSS.MS-PS1-1

Hydrogen Peroxide has a chemical formula of H₂O₂. Which atoms make up this compound?

• 2 atoms of hydrogen and 1 atom of oxygen

• 1 atom of hydrogen and 2 atoms of oxygen

• 2 atoms of hydrogen and 2 atoms of oxygen

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NGSS.MS-PS1-1

Why does CH₄ not have a subscript of 1 after the C, for carbon?

• Because it is missing.

• Because C represents 1 atom of carbon and a subscript is not necessary.

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Sucrose, or table sugar, has a chemical formula of C₁₂H₂₂O₁₁ . How many atoms of carbon are there?

• 11

• 12

• 22

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NGSS.MS-PS1-1

Which of the following statements about molecules is true?

• All molecules contain atoms of only one element.

• There is always an equal number of each element in a molecule.

• The atoms in a molecule cannot be separated from each other by physical means.

• Two or more molecules combine to form an atom.

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NGSS.MS-PS1-1