The chart below lists some substances and their symbols. How many of these substances are examples of elements?

• 1

• 2

• 3

• 4

What makes elements and compounds different from mixtures? Elements & compounds-

• have a constant composition (pure substances)

• are made of gases

• Will not change when heated

• conduct electric current

What is the relationship between molecules and atoms?

• Molecules are combinations of two or more atoms.

• Molecules are the parts that make up atoms

• Molecules are the gaseous parts of atoms

• Molecules are atoms that have a positive charge

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In the diagrams provided, the circles of different colors represent the atoms of different elements. Which diagram represents a mixture?

• I

• II

• III

• IV

Mixtures are different than pure substances because mixtures-

• have lower boiling points

• can be separated physically

• are less dense than pure substances

• contain only one type of atom

Which answer correctly matches the diagram with the correct description?

• Q- Multiple compounds R-A single element S-An element and a compound T- A single compound

• Q- A single element, R- An element and a compound S-A single compound T-Multiple compounds

• Q- A single compound, R- A single element, S- Multiple compounds, T- An element and a compound

• Q- An element and a compound, R- a single compound, S- a single element, T- multiple compounds

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NGSS.MS-PS1-1

Which of the following is true of oxygen?

• Oxygen is an element because its most basic unit is a single type of atom

• Oxygen is a compound because its most basic unit is a single type of atom.

• Oxygen is a mixture because its most basic unit contains more than one particle.

• Oxygen is a compound because its most basic unit contains more than one type of particle.

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Humans absorb oxygen from the air they breathe in and exhale carbon dioxide gas, CO2. Carbon dioxide gas is

• an element made of carbon and oxygen atoms.

• a solution made of carbon and oxygen atoms.

• a compound of carbon and oxygen atoms.

• a mixture of carbon and oxygen atoms.

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Sam's mother is cooking breakfast in a cast-iron frying pan. If the pan is made only of iron, what can Sam conclude?

• The pan is a pure substance with the chemical symbol Ir.

• The pan is a pure substance with the chemical symbol I.

• The pan is a pure substance with the chemical symbol F.

• The pan is a pure substance with the chemical symbol Fe.

Which of the following represents an element?

• H₂O
• H₂
• NaCl
• CaCO₃

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NGSS.MS-PS1-1