Hydrocarbon Families: Alkanes and Alkenes

Hydrocarbons are organized into families based on their chemical properties and functional groups. These families share similar characteristics and follow specific patterns.

Definition: A hydrocarbon family is a group of organic compounds with the same functional group and similar chemical properties.

Key features of hydrocarbon families include:

1. Shared general formula
2. Molecular formulae differing by CH₂ between neighboring compounds
3. Gradual variation in physical properties, such as boiling points
4. Similar chemical properties

The two main hydrocarbon families discussed are alkanes and alkenes.

Alkanes

Definition: Alkanes are saturated hydrocarbons with only single bonds between carbon atoms.

Characteristics of alkanes:

• General formula: CnH₂n+₂
• Saturated, meaning all carbon atoms are joined by single bonds
• Less reactive compared to alkenes

Alkenes

Definition: Alkenes are unsaturated hydrocarbons with at least one double bond between carbon atoms.

Characteristics of alkenes:

• More reactive than alkanes due to the presence of double bonds
• Can be tested using bromine water

Example: To test for alkenes, add bromine water to the compound. If the orange color of bromine water turns colorless, it indicates the presence of a C=C double bond in the molecule.

Highlight: The differences between alkanes and alkenes in hydrocarbons primarily lie in their bond structure and reactivity.

Molecular Structures and Fractional Distillation

This section explores the molecular structures of alkanes and the process of fractional distillation used to separate crude oil into useful fractions.

Molecular Structures of Alkanes

The first four alkanes in the series are:

1. Methane (CH₄)
2. Ethane (C₂H₆)
3. Propane (C₃H₈)
4. Butane (C₄H₁₀)

Each alkane has a unique structural formula and ball-and-stick model representation, illustrating the arrangement of carbon and hydrogen atoms in the molecule.

Fractional Distillation of Crude Oil

Definition: Fractional distillation is the process used to separate crude oil into simpler and more useful mixtures.

The fractional distillation process of crude oil explained:

1. Heated crude oil enters a tall fractionating column
2. The column is hot at the bottom and cooler towards the top
3. Vapors from the oil rise through the column
4. Vapors condense when they become cool enough
5. Liquids are led out of the column at different heights

Highlight: The separation of crude oil components is based on their boiling points, which are determined by the strength of intermolecular forces in each fraction.