Question

name:
date:
part 1: multiple choice (1 - 10)

1. what is the smallest unit of an element that still has all its properties?

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

1. which of the following is a compound?

a. o2 b. h2o c. he d. fex

1. a molecule is made up of:

a. only one atom b. two or more atoms bonded together c. a mixture d. neutrons and proton

1. which of the following is an element?

a. carbon dioxide b. water c. iron d. table salt

1. when atoms of different elements combine, they form a:

a. solution b. compound c. mixture d. gas

1. which of these is not a compound?

a. nacl b. h2 c. co2 d. c6h12o6

1. the chemical formula h2o tells us:

a. 1 atom of hydrogen and 2 of oxygen
b. 2 atoms of hydrogen and 1 of oxygen
c. 2 molecules of oxygen
d. 1 molecule of hydrogen

1. what holds atoms together in a molecule?

a. gravity b. electric current c. chemical bonds d. magnetic force

1. which is an example of a molecule that contains only one element?

a. o2 b. co3 c. nacl d. h4o4

1. what do subscripts in a chemical formula show?

a. number of atoms b. number of molecules c. atomic mass d. type of element
part 2: true or false (11 - 15)

1. all compounds are molecules, but not all molecules are compounds.

Explanation:

• Question 1: An atom is the smallest unit of an element that retains its properties. A molecule is made of atoms, a compound is a combination of elements, and a proton is a sub - atomic particle.
• Question 2: A compound is a substance formed when two or more elements chemically bond. \(O_2\) is an element (diatomic molecule of oxygen), \(H_2O\) is a compound (hydrogen and oxygen), \(He\) is an element, and \(FeX\) is not a standard chemical formula.
• Question 3: A molecule is defined as two or more atoms bonded together.
• Question 4: An element is a pure substance. Carbon dioxide (\(CO_2\)) and water (\(H_2O\)) are compounds, table salt (\(NaCl\)) is a compound, and iron (\(Fe\)) is an element.
• Question 5: When atoms of different elements combine chemically, they form a compound. A solution is a homogeneous mixture, a mixture is a physical combination, and gas is a state of matter.
• Question 6: \(H_2\) is a diatomic molecule of an element (hydrogen), while \(NaCl\) (\(Na\) and \(Cl\)), \(CO_2\) (\(C\) and \(O\)), and \(C_6H_{12}O_6\) (\(C\), \(H\), and \(O\)) are compounds.
• Question 7: The formula \(H_2O\) means 2 hydrogen atoms and 1 oxygen atom.
• Question 8: Chemical bonds (such as covalent, ionic) hold atoms together in a molecule. Gravity is a universal force, electric current is related to electron flow, and magnetic force is related to magnetic materials.
• Question 9: \(O_2\) contains only the element oxygen. \(CO_3\) (if it existed as a stable molecule) would have \(C\) and \(O\), \(NaCl\) has \(Na\) and \(Cl\), and \(H_4O_4\) (not a standard formula) would have \(H\) and \(O\).
• Question 10: Subscripts in a chemical formula show the number of atoms of each element. The type of element is shown by the symbol, not the subscript.
• Question 11: Compounds are made of two or more different elements (so they are molecules), but molecules like \(O_2\) (same - element atoms) are not compounds.

Answer:

1. B. Atom
2. B. \(H_2O\)
3. B. Two or more atoms bonded together
4. C. Iron
5. B. Compound
6. B. \(H_2\)
7. B. 2 atoms of hydrogen and 1 of oxygen
8. C. Chemical bonds
9. A. \(O_2\)
10. A. Number of atoms
11. T (True)