Question

score: —/20
part a: multiple choice (1 point each)
choose the best answer. circle the letter of your choice.

1. the smallest part of an element that still has its properties is called a

a. cell b. atom c. molecule d. compound

1. which of the following is made of only one kind of atom?

a. water b. salt c. iron d. sugar

1. when two or more atoms join together, they form a —.

a. mixture b. molecule c. element d. solution

1. which of the following is not a compound?

a. water (h₂o) b. carbon dioxide (co₂) c. oxygen (o₂) d. salt (nacl)

1. a molecule always contains two or more — joined together.

a. elements b. atoms c. compounds d. ions

1. which statement is true?

a. all molecules are compounds.
b. some molecules are not compounds.
c. all compounds are elements.
d. elements and compounds are the same.

1. when elements combine chemically, what is formed?

a. a mixture b. a compound c. an element d. a metal

1. air is an example of a —.

a. compound b. mixture c. molecule d. element

1. which of these describes an element?

a. can be broken into simpler substances
b. made of one type of atom
c. always a mixture
d. made of different atoms

Explanation:

1. An atom is the smallest part of an element that retains its properties.
2. Iron is an element, made of only one kind of atom.
3. When two or more atoms join, they form a molecule.
4. Oxygen (\(O_2\)) is an element (a diatomic molecule of the same - type atoms), not a compound.
5. A molecule is formed by two or more atoms.
6. Some molecules (like \(O_2\)) are not compounds (compounds have different types of atoms chemically bonded).
7. When elements combine chemically, a compound is formed.
8. Air is a mixture of gases (like \(N_2\), \(O_2\), \(CO_2\) etc.).
9. An element is made of one type of atom.

Answer:

1. b. Atom
2. c. Iron
3. b. Molecule
4. c. Oxygen (\(O_2\))
5. b. Atoms
6. b. Some molecules are not compounds.
7. b. A compound
8. b. Mixture
9. b. Made of one type of atom