Unit 1 Review

What is a small particle that is known as the basic building block of matter?

• molecule

• compound

• element

• atom

Answer explanation

An atom is a small particle that is known as the basic building block of matter, making it the correct choice.

H₂O is most accurately described as a ___________________.

• molecule

• compound

• element

• atom

Answer explanation

H2O is most accurately described as a compound because it is composed of two different elements, hydrogen and oxygen, chemically bonded together.

Which of the following is the most accurate statement?

• everything is both a molecule and a compound

• nothing can be both a molecule and a compound

• all compounds are also molecules

• All molecules are also compounds

Answer explanation

The most accurate statement is that all compounds are also molecules, as compounds are made up of molecules. Not all molecules are compounds, but all compounds are molecules.

Oxygen, Nitrogen, Hydrogen, and Calcium are all examples of ______________________.

• molecules

• compounds

• atoms

• elements

Answer explanation

Oxygen, Nitrogen, Hydrogen, and Calcium are all examples of elements, as they are pure substances made up of only one type of atom.

Which one of the following is a compound?

• NaCl

• O2

• Hydrogen

• He2

Answer explanation

NaCl is a compound because it is composed of two different elements, sodium and chlorine, chemically bonded together.

Molecules and compounds are created when multiple atoms bond together, but how are they different?

• Compounds have to have atoms from different elements bonded together

• Molecules have to have atoms from different elements bonded together

• They are the same and there is no difference

• Molecules are building blocks of compounds

Answer explanation

Compounds have to have atoms from different elements bonded together

Which of these models can be described as a compound?

• water

• carbon dioxide

• amonia

• methane

• All of them are compounds

Answer explanation

All of the models can be described as compounds because they are made up of two or more different elements chemically bonded together.

Which of these is only a molecule and not a compound?

• a

• b

• c

• d

Answer explanation

The correct choice is b because it is a molecule made up of only one type of atom, while compounds consist of different types of atoms bonded together.

How many Hydrogen atoms are present in H₂0?

• 2

• 4

• 1

• 0

Answer explanation

There are 2 Hydrogen atoms present in H2O because each water molecule contains 2 Hydrogen atoms.

How many different elements are represented in the compound?
Fe₃O₄

• 2

• 3

• 1

• 4

Answer explanation

The compound Fe3O4 consists of iron (Fe) and oxygen (O), so there are 2 different elements represented in the compound.