Unit 4 Quiz Study Guide – ANSWER KEY

Vocabulary Review

  1. A mixture is / is not(circle one) a chemical combining of substances.
  2. In a compound the atoms / molecules(circle one) are chemically/ physically(circle one) combined so that the elements that make up the compound retain / lose(circle one) their identities and do / do not(circle one) take on a new set of properties.
  3. The smallest identifiable unit of a compound is a(n) __molecule__, which is made up of __2+ atoms___ which are chemically bonded.
  4. True or false: A mixture is always made up of a combination of elements.
  5. In a mixture, the substances lose / retain(circle one) their identities.
  6. In a mixture the substances involved can / cannot (circle one) be separated by a simple physical process. In a compound the elements involved can / cannot(circle one) be separated by a simple physical process because the elements are physically combined / chemically bonded(circle one).
  7. True or False: An element can be broken down into a simpler substance. (unless you mean p, n, e)
  8. The smallest identifiable unit of an element is a(n) __atom______.
  1. From the following list of substances, circle ones that are elements:

SilverWaterOxygenAir

Carbon dioxideHydrogenGoldSulfur

CarbonSugarMagnesiumSalt

  1. Classify the following as pure substances or mixtures.

Air - MixWater – PureMercury - PureGasoline - Mix

Sugar - PureOxygen- PureGold - PureSaltwater-Mix

Classify each of the following substances as an element, compound, homogeneous mixture or heterogeneous mixture.

  1. SandHet Mix6. Sugar waterHomo Mix11.
  1. Soda just openedHet Mix7. CalciumElement
  1. Oxygen(O2)Element(molecule)8. Lithium Iodide (LiI)Compound
  1. Apple Pie Het Mix9. Hydrogen peroxide (H2O2)Compound

12.

  1. SilverElement10. Carbon dioxide (CO2) Compound

Classify the following compounds as ionic (I), covalent (C), metallic (M)

CaCl2 ICO2 CNi M

H2O CK2O INaF I Fe M CH4 C SO3 C LiBrI MgO I P2O5 C

HCl I(hydrogen acts a metal in this case)KI IN2O3 C

Cu MNO2 CAu M

  1. What is electronegativity?How badly an atom wants an electron
  2. What does it mean to say a bond is polar? Unequal sharing of electrons (one of the elements has a higher electronegativity than the other so it “pulls” more on the electron)
  3. How are ionic bonds and covalent bonds different? What are the unique properties of each? Ionic bonds between metal + nonmetal, covalent bonds between nonmetal + nonmetal. Covalent bonds have lower melting/boiling points and are more flammable. Ionic bonds have higher conductivity.
  4. How does a polar bond differ from a covalent bond? Nonpolar covalent bond is equal sharing (atoms have same/similar EN) polar covalent bond is unequal sharing of electrons
  5. How do electronegativity values help us determine the type of bond created? If the values are close, it’s an equal sharing, if they are very far apart, one element is so “strong” it’s just going to take the electron from the other one (ionic)
  1. For each of the following sets of elements, identify the element expected to be most electronegative (EN) and which is expected to be least electronegative (EN).
  1. K, Sc, Camost EN= __Sc___least EN=__K__
  1. Br, F, Atmost EN= __F___least EN=___At___
  1. C, O, Nmost EN= __O___least EN=__C____
  1. For each of the following molecules, determine if it is covalent, polar, or ionic. Show your work by listing the electronegativities of each element in the bond. (use the table below)

Molecule / Electronegativity Values / Difference in Electronegativity / Bond Type
H – Cl / H:2.1
Cl:3.0 / 3.0 – 2.1 = 0.9 / Polar Covalent
H – H / H:2.1
H:2.1 / 2.1 – 2.1 = 0 / Nonpolar Covalent
H - I / H:2.1
I:2.5 / 2.5 – 2.1 = 0.4 / Nonpolar Covalent
Cl - Cl / Cl:3.0
Cl:3.0 / 3.0 – 3.0 = 0 / Nonpolar Covalent
C – O / C:2.5
O:3.5 / 3.5 – 2.5 = 1 / Polar Covalent