Quiz about Case 14 Vocabulary: Molecules and Compounds

Question 1

What is the smallest unit of an element that retains the properties of that element?

Accepted Answer

Atom

Answer

Molecule

Answer

Compound

Answer

Mixture

Question 2

Which term describes a substance made of only one kind of atom?

Accepted Answer

Element

Answer

Compound

Answer

Mixture

Answer

Molecule

Question 3

What is a chemical bond?

Accepted Answer

A force that holds atoms together

Answer

A type of atom

Answer

A mixture of substances

Answer

A chemical formula

Question 4

Which of the following is a pure substance?

Accepted Answer

Oxygen gas ( $$O_2$$ )

Answer

Air

Answer

Salt water

Answer

Soil

Question 5

What does a subscript in a chemical formula represent?

Accepted Answer

The number of atoms of an element in a molecule

Answer

The number of molecules

Answer

The type of chemical bond

Answer

The total mass

Question 6

Which of the following best describes a mixture?

Accepted Answer

A combination of two or more substances that are not chemically bonded

Answer

A substance made of only one type of atom

Answer

A substance with a fixed chemical formula

Answer

A molecule with two atoms

Question 7

What does the coefficient in a chemical equation indicate?

Accepted Answer

The number of molecules or formula units

Answer

The number of atoms in a molecule

Answer

The type of element

Answer

The ratio of elements

Question 8

Which of the following is an example of a compound?

Accepted Answer

$$H_2O$$

Answer

$$O_2$$

Answer

Gold

Answer

Air

Question 9

Which term refers to the arrangement of atoms in a molecule?

Accepted Answer

Structure

Answer

Ratio

Answer

Coefficient

Answer

Subscript

Question 10

If a chemical formula is $$CO_2$$ , what does the "2" represent?

Accepted Answer

Two oxygen atoms

Answer

Two carbon atoms

Answer

Two molecules

Answer

Two compounds

Question 11

Which of the following best explains why $$NaCl$$ is considered a compound and not a mixture?

Accepted Answer

The elements are chemically bonded in a fixed ratio.

Answer

It contains only one type of atom.

Answer

It can be separated by physical means.

Answer

It is made of molecules.

Question 12

Given the chemical formula $$C_6H_{12}O_6$$ , what is the ratio of hydrogen to oxygen atoms?

Accepted Answer

2:1

Answer

1:1

Answer

6:12

Answer

12:6

Question 13

How would you distinguish between a pure substance and a mixture using their properties?

Accepted Answer

By their melting points and ability to be separated physically

Answer

By their color

Answer

By their size

Answer

By their mass

Question 14

If you have a sample of water ( $$H_2O$$ ) and a sample of salt water, which is a mixture and which is a pure substance? Explain your reasoning.

Accepted Answer

Water is a pure substance; salt water is a mixture because salt water can be separated physically.

Answer

Both are mixtures because they contain more than one element.

Answer

Both are pure substances because they are liquids.

Answer

Salt water is a pure substance; water is a mixture.

Question 15

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

Accepted Answer

Molecules can be made of the same or different elements; compounds are molecules made of different elements.

Answer

Molecules are always made of different elements, compounds are not.

Answer

Compounds are always gases, molecules are always solids.

Answer

Molecules are mixtures, compounds are pure substances.

Question 16

A student is given a chemical formula $$2H_2O$$ . What does the "2" in front of $$H_2O$$ represent, and how many hydrogen atoms are present in total?

Accepted Answer

2 molecules, 4 hydrogen atoms

Answer

2 molecules, 2 hydrogen atoms

Answer

2 atoms, 2 hydrogen atoms

Answer

2 molecules, 2 oxygen atoms

Question 17

A scientist wants to create a new substance by combining two elements. What must happen for the result to be considered a compound rather than a mixture?

Accepted Answer

The elements must chemically bond in a fixed ratio.

Answer

The elements must be physically mixed together.

Answer

The elements must remain unchanged.

Answer

The elements must be gases.

Question 18

You are given two samples: one is a shiny metal, and the other is a white powder that dissolves in water. How would you determine which is an element and which is a compound?

Accepted Answer

Check if they have a fixed chemical formula and can be broken down into simpler substances.

Answer

Test if they can be separated by physical means.

Answer

See which one is heavier.

Answer

Observe their color.

Question 19

A student mixes iron filings and sulfur powder. After mixing, the properties of iron and sulfur remain unchanged. What does this tell you about the type of substance formed, and why?

Accepted Answer

It is a mixture because the original properties remain.

Answer

It is a compound because the properties are new.

Answer

It is a pure substance because it looks uniform.

Answer

It is a molecule because it contains two elements.

Question 20

Given the chemical formula $$C_2H_6O$$ , explain how you would determine the number of each type of atom present and what this tells you about the structure of the molecule.

Accepted Answer

Use the subscripts to count atoms; it shows the ratio and possible arrangement of atoms in the molecule.

Answer

Count the letters only; it tells you nothing about structure.

Answer

Add the numbers together; it gives the total mass.

Answer

Ignore the subscripts; all atoms are equal.

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