**Fractional Distillation**

**Explanation:**

Fractional distillation is the process of separating a mixture of different hydrocarbons into fractions based on their boiling points. This process is commonly used in the petroleum industry to separate crude oil into its various components, such as gasoline, diesel, and kerosene.

1. **Introduction to Fractional Distillation:**
- Fractional distillation is a physical separation technique that exploits the differences in boiling points of the constituents in a mixture.
- It is based on the principle that different substances have different boiling points, and by carefully controlling the temperature, the mixture can be separated into its individual components.
- In the case of hydrocarbons, the boiling points increase with the increase in the length of the carbon chains.

2. **Process of Fractional Distillation:**
- The mixture of hydrocarbons is heated in a fractionating column, which is a tall vertical tower with several trays or plates.
- As the mixture is heated, the substances with lower boiling points vaporize first and rise up the column.
- The column is hotter at the bottom and cooler at the top, creating a temperature gradient.
- As the vapors rise up the column, they condense on the cooler trays.
- The substances with lower boiling points condense on the higher trays, while those with higher boiling points condense on the lower trays.
- Each tray collects a separate fraction, which is then collected and further processed.

3. **Separation into Fractions:**
- The different fractions collected during fractional distillation have different compositions and properties.
- The fraction with the lowest boiling point, which consists mainly of gases like methane, ethane, and propane, is collected at the top of the column.
- As the temperature increases down the column, the fractions collected include gasoline, kerosene, diesel, and heavier oils.
- The heaviest fraction, which consists of long-chain hydrocarbons, is collected at the bottom of the column.

4. **Uses of Fractional Distillation:**
- Fractional distillation is an essential process in the petroleum industry for the production of various fuels and other petroleum products.
- The fractions obtained from crude oil are further processed to obtain gasoline, diesel, jet fuel, lubricants, and other valuable products.
- It is also used in the production of chemicals, such as ethylene and propylene, which are important raw materials in the manufacturing of plastics.

In conclusion, fractional distillation is the most appropriate term to describe the process of separating a wide range of different hydrocarbons into fractions. It is a widely used technique in the petroleum industry to obtain various valuable products from crude oil.

The hydrocarbons which condense over a temperature range is called fraction ........ because they are whole apart
each of the fraction has special uses...... separating the mixture of substances in crude oil into fraction by evaporation and condensation............is fractional distillation