The document defines alkenes as hydrocarbons containing one or more carbon-carbon double bonds. Alkenes have trigonal planar molecular geometry at the double bond with 120° bond angles. Ethene and propene are examples of alkenes with double bonds between the first two carbons. Alkenes exist as colorless gases with fewer than 5 carbons, liquids with 5 or more carbons, and solids with 15 or more carbons depending on their molecular structure and size.

1. Alkenes
By: Elly Terry

2. Definitions
• Hydrocarbons are compounds containing hydrogen and
carbon.
• Alkenes are hydrocarbons containing a double carbon-
carbon bond.
• The C=C double bonds have a triganol planar molecular
geometry with 120 bond angles.
• C=C double bonds have one sigma and one pi bond.
• Unlike C-C single bonds, C=C double bonds are unable to
rotate freely. This is because of the overlapping of sigma and
pi bond orbitals.
• If there are four or more carbons in an alkene, the alkene can
have isomers.

3. Ethene
• Ethene, C2H4, is an alkene with a double bond in-
between the two carbons.
• The condensed structure is CH2=CH2.
• The H-C-H bond angle is 120°.

4. Propene
• Propene, C3H6, is an alkene because it has a
double bond in-between the first two carbons.
• The condensed structure for propene is
CH2=CHCH3.

5. Physical States of Alkenes
• Ethene, Propene, and Butene are colorless gases.
• If an alkene has 5 or more carbons, it is a liquid.
• Alkenes with fifteen or more carbons exist as
solids.

6. Summary
• In conclusion, alkenes are unsaturated
hydrocarbons with one or more carbon-
carbon double bond. Their double bond
is made up of one sigma bond and one pi
bond. The pi bond is what differentiates
an alkene from an alkane.