NC 8th Science 8.P.1 Review

Which is the best example of a pure substance?

• peanuts

• milk

• gold

• air

This chart represents several compounds and their chemical formulas. Which explains why the same elements can create many different compounds?

• Elements combine in the same way to produce a variety of substances.

• Elements have the ability to change electron size in order to combine with many different elements.

• Elements combine in a multitude of ways to produce compounds that account for all living and nonliving substances.

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Why does hydrogen (H) have a different subscript in each substance?

• The subscript indicates the number of hydrogen atoms in each substance.

• The subscript indicates the number of mixtures that the hydrogen is forming.

• The subscript indicates the number of compounds that the hydrogen is forming.

• The subscript indicates whether the hydrogen is forming a compound or a mixture.

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The table shows the chemical formulas for several common household substances. Which two elements make up household ammonia?

• neon and helium

• neon and hydrogen

• nitrogen and helium

• nitrogen and hydrogen

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The table below shows common compounds and their chemical formulas. Which can best be concluded from this information?

• Some compounds contain only one element.

• All compounds contain the same number of elements.

• Elements combine in many ways to form different compounds.

• Elements combine in the same way to form different compounds.

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Sodium (Na) and chlorine (Cl) combine to form table salt (NaCl). How many sodium (Na) atoms are there for every chlorine atom (Cl)?

• two sodium (Na) atoms for every one chlorine (Cl) atom

• one sodium (Na) atom for every one chlorine (Cl) atom

• one sodium (Na) atom for every two chlorine (Cl) atoms

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In which state of matter will the atoms of an element be tightly packed together?

• gas

• liquid

• solid

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How are atoms combined in a mixture?

• chemically combined and cannot be separated

• physically combined and can be separated

• chemically combined and can be separated

How can mixtures best be described?

• made of one element

• made of different elements that are all chemically bonded together

• made of different elements that are not all chemically bonded together

Hydrogen peroxide (H₂O₂) and water (H₂O) both contain hydrogen (H) and oxygen (O). Why are they different compounds?

• Hydrogen peroxide contains one more oxygen than water.

• Hydrogen peroxide contains two more oxygens than water.

• Hydrogen peroxide contains one less oxygen than water.

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