Topic: Properties of Hydrocarbons

Do Now: Quiz

Hydrocarbons

IMF?

Polar or Nonpolar?

Dispersion Forces (van der waals)

Properties of Covalent Substances(also called molecular substances)

• Low melting points, low boiling points• Poor conductors of heat & electricity• May be soft or brittle• Generally nonpolar

– van der Waals forces• Tend to dissolve in nonpolar solvents• React more slowly than ionic compounds

Increasing in Size = Increasing IMF = increasing BP/MP

Properties of Alkanes• Low Reactivity

–Except readily undergo combustion (fuels)• Nonpolar – don’t dissolve well in water• Low melting & low boiling points

–both increase with molecular mass• High vapor pressures

Properties of Alkanes

• Change systematically with # of C’s

• As # of C’s increases, boiling point increases– molecules get heavier so harder to change into gas

phase

A. Low melting pointB. High melting pointC. Soluble in polar solventsD. Insoluble in nonpolar solvents

Which property is generally characteristic of an organic compound?

Correct response = A

A. CH4

B. C2H6

C. C3H8

D. C4H10

Which of the following compounds has the highest boiling point?

Correct answer = D

nonpolar coval cmpd:

• bp depends on strength of van der Waals interactions

• van der Waals forces ↑ as size of molecule ↑

• bigger molecule = bigger electron cloud

Properties of Alkenes

• Nonpolar – low solubility in H2O

• fairly low melting and low boiling points

• More reactive than alkanes :– double bond is site of reactivity

Properties of Alkynes

• Nonpolar – low solubility in H2O

• fairly low melting and low boiling points

• More reactive than alkenes :– triple bond is site of reactivity