Unit 4 - Topic 1 - Physical Properties and Trends

Question 1

Where do intramolecular and intermolecular bonds occur?

Answer 1

Intramolecular bonds occur between atoms within a molecule

Intermolecular bonds occur between molecules - these determine the physical properties of compounds

Question 2

Give 3 examples of intramolecular bonds

Answer 2

Covalent bonds, ionic bonds, metallic bonds

Question 3

Give 3 examples of intermolecular bonds (increasing strength)

Answer 3

Dispersion forces
Dipole Dipole forces
Hydrogen bonds

Question 4

What is a dispersion force?

Answer 4

Non-polar
Instant dipoles are formed due to movement of electrons (they are present between ALL molecules)

Question 5

What are dipole-dipole forces?

Answer 5

Polar
Negative and positive ends of molecules are attracted to one another

Question 6

What are hydrogen bonds?

Answer 6

Where Hydrogen is covalently bonded to Fluorine, Oxygen, or Nitrogen (FON)
BECAUSE of this = extremely polar

Question 7

What makes a bond polar?

Answer 7

Electronegativity difference >0.4
Assymetrical structure

Question 8

What are the types of properties that are impacted by intermolecular forces? Is each one physical or chemical?

Answer 8

1. Melting and boiling point (physical)
2. Solubility (chemical)
3. Volatility (chemical)

Question 9

*What is the effect of functional groups on melting and boiling points?

Answer 9

As the strength of intermolecular forces within a compound’s functional group increases, the boiling and melting point also increases.

Compounds with dispersion forces = lower MP/BP
Compounds with hydrogen bonds = higher MP/BP

Question 10

*What is the effect of chain length on a compound’s melting and boiling points? (and why?)

Answer 10

As the chain length increases, BP also increases

Increasing the number of carbons increases the strength of dispersion forces within the compound, requiring more energy to break these bonds.

Question 11

*Effect of branching