Topic: Properties of Hydrocarbons Do Now: Quiz

Hydrocarbons

molecular 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 point B.High melting point C.Soluble in polar solvents D.Insoluble in nonpolar solvents Which property is generally characteristic of an organic compound? Correct response = A

A.CH 4 B.C 2 H 6 C.C 3 H 8 D.C 4 H 10 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 bp depends on strength of van der Waals interactions van der Waals forces ↑ as size of molecule ↑ van der Waals forces ↑ as size of molecule ↑ bigger molecule = bigger electron cloud bigger molecule = bigger electron cloud

Properties of Alkenes Nonpolar – low solubility in H 2 O fairly low melting and low boiling points More reactive than alkanes : – double bond is site of reactivity

Properties of Alkynes Nonpolar – low solubility in H 2 O fairly low melting and low boiling points More reactive than alkenes : – triple bond is site of reactivity