Name __________________
Date _______ Block _____
Vocabulary to be placed on flash cards and then onto your flash card ring. polar molecule nonpolar molecule partial charge intermolecular forces electronegativity dipole diatomic molecule
Lesson 15 – Attractive Molecules – Attractions Between Molecules
Key Question – Why do some molecules smell while others do not?

A polar molecule has partial charges distributed within the molecule. Part of the molecule is positively charged and part of the molecule is negatively charged.

A polar molecule is attracted to a charged wand.

A nonpolar molecule has no reaction to a charged wand.

The polarity of a molecule has something to do with smell.

The attraction between individual molecules is an intermolecular force.

1.
A student observed that liquid “A” is attracted to a charged wand, but liquid “B” was not. Write true or false for each statement. a) _______________Liquid A is polar. b) _______________Liquid B is polar. c) _______________Liquid A would make a bead on waxed paper. d) _______________Liquid B would spread out on waxed paper. e) _______________Liquid A could be water. f) _______________Liquid B could be water.
Lesson 16 – Polar Bears and Penguins –Electronegativity and Polarity
Key Question – What makes a molecule polar?

The tendency of an atom to attract shared electrons is called electronegativity.

A polar molecule is called a dipole because it has two poles – a positive end and a negative end.

There are two types of covalent bonds: nonpolar covalent and polar covalent.

When two atoms with identical electronegativities bond together, the attraction of the shared electrons is identical. They form a nonpolar bond.
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When atoms with different electronegativities bond together, they form a polar covalent bond.
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In an ionic bond, the electrons are transferred to the more electronegative atom.
2. Tell whether the bond formed between each pair of atoms is polar or nonpolar. a. H-O __________ b. H-H ____________

Lesson 17 – Thinking (Electro)Negatively – Electronegativity Scale
Key Question – How can electronegativity be used to compare bonds?

Each element has an electronegativity value between 0 and 4.

The electronegativity scale can be used to compare the electronegativity of different elements.
 Molecules made of two atoms are called diatomic molecules.

The electronegativity scale can also be used to compare and classify bonds.
 If there is very little or no difference in electronegativity between atoms, then the bond is considered to be nonpolar covalent.
 The larger the electronegativity difference, the more polar the bond.
 When the electronegativity difference between two atoms is greater than 2.1, the bond is considered to be ionic.
3. Draw either a partial positive or a partial negative charge above each atom in the following pairs of atoms. Use the electronegativity scale to look up the electronegativity values of each element. a. H−Cl b. C−O
4. For each pair of atoms, tell what type of bond would form (nonpolar covalent, polar covalent, or ionic). Use the electronegativity scale to look up the electronegativity values of each element. a. H and Cl __________________ b. Na and F__________________
Lesson 18 – I Can Relate – Polar Molecules and Smell
Key Question – What does polarity have to do with smell?

Small asymmetrical molecules with polar bonds are polar.

Molecules that are symmetrical in every way are nonpolar.

Molecules that smell tend to be polar. The polarity of molecules help them attach to receptor sites in the nose.
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Polar molecules dissolve in water. This may allow polar molecules to dissolve in the mucous membrane of the nose.
5. a. Is the NH
3
(ammonia) molecule polar or non polar? _____________
b. Would you expect NH
3
(ammonia) to smell? Explain.
6. a. Is the CH
4
(methane) molecule polar or non polar? _____________ b. Would you expect CH
4
(methane) to smell? Explain.