Question

1. which of the following is not a compound?

a. carbon dioxide (co₂)
b. sodium chloride (nacl)
c. nitrogen gas (n₂)
d. ammonia (nh₃)

1. when two or more elements combine chemically, they form:

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

1. a crystal is:

a. a solid with atoms arranged in a repeating pattern
b. a liquid that glows
c. a random arrangement of atoms
d. a melted mineral

1. the repeating pattern in a crystal is called a:

a. formula
b. crystal lattice
c. bond line
d. element grid

1. which of the following is an example of a crystal?

a. glass
b. sugar
c. wood
d. plastic

1. what happens to bonds when a chemical reaction occurs?

a. they stay the same
b. they break and new ones form
c. they disappear
d. they freeze in place

1. compounds have properties that are:

a. the same as their elements
b. usually different from the elements they form
c. random
d. based on color

1. which of the following is a molecule but not a compound?

a. o₂
b. co₂
c. h₂o
d. nacl

1. metals tend to ______ electrons when bonding.

a. gain
b. lose
c. share
d. split

Explanation:

• Question 8: A compound is a substance formed when two or more elements chemically combine. \(CO_2\) (carbon + oxygen), \(NaCl\) (sodium + chlorine), \(NH_3\) (nitrogen + hydrogen) are compounds. \(N_2\) is an element (diatomic molecule of nitrogen).
• Question 9: When elements combine chemically, they form a compound. A mixture is a physical combination, a solution is a homogeneous mixture, and a crystal is a solid - state form.
• Question 10: A crystal is a solid with atoms arranged in a repeating pattern. Liquids don't have a fixed crystal - like structure, and random atom arrangements are not crystals.
• Question 11: The repeating pattern in a crystal is called a crystal lattice. A formula represents the composition, a bond line is in structural formulas, and element grid is not a standard term.
• Question 12: Sugar has a crystalline structure. Glass is an amorphous solid, wood is a complex organic material (not a simple crystal), and plastic is an amorphous polymer.
• Question 13: In a chemical reaction, bonds break (in reactants) and new bonds form (in products).
• Question 14: Compounds have properties usually different from the elements they form. For example, \(H_2\) (flammable) and \(O_2\) (supports combustion) form \(H_2O\) (non - flammable and doesn't support combustion in the same way).
• Question 15: \(O_2\) is a molecule (diatomic) but not a compound (only one type of element). \(CO_2\), \(H_2O\), \(NaCl\) are compounds.
• Question 16: Metals tend to lose electrons when bonding (to form positive ions in ionic bonding).

Answer:

• 8. C. Nitrogen gas (\(N_2\))
• 9. B. A compound
• 10. A. A solid with atoms arranged in a repeating pattern
• 11. B. Crystal lattice
• 12. B. Sugar
• 13. B. They break and new ones form
• 14. B. Usually different from the elements they form
• 15. A. \(O_2\)
• 16. B. Lose