Hydrocarbons Science Notes Class 10

Hydrocarbons

Hydrocarbons are the compounds formed by the covalent bonding of Hydrogen and Carbon atoms.

For example: CH₄ is a hydrocarbon because it is formed when one carbon atom combines with four atoms of hydrogen.

Functional Group and Homologous Series

Functional group is an atom or a group of atoms that define the chemical properties of an organic compound, when added to it. Some examples of functional group are: Alcohol (-OH), Aldehyde (-CHO), Ether (-O-), etc.

Homologous series is a series of organic compounds in which all the organic compounds can be represented by the same general formula and each successive homologue differs from the preceding by a -CH2 group or 16 molecular weight.
For example: Alkane is a homologous series having the general formula C_nH_2n+2. Each member of a homologous series is called a homologue.

Saturated and Unsaturated Hydrocarbons

On the basis of bonds present in between any two carbon atoms of the hydrocarbons, they are classified into two types:

Saturated Hydrocarbons:
Saturated Hydrocarbons are those hydrocarbons containing only single bond in between the connected carbon atoms. They are also known as alkanes or paraffins. The general formula for alkane is C_nH_2n+2. Here, n represent the number of carbon atoms.
Example: alkane (methane, ethane, propane, etc.)
Unsaturated Hydrocarbons:
Unaturated Hydrocarbons are those hydrocarbons containing either double or triple covalent bond in between the connected carbon atoms.
Examples: alkene (ethene, propene, etc.) and alkyne (ethyne, propyne, etc.)

Alkane

Alkane is a saturated hydrocarbon having the general formula C_nH_2n+2. The suffix of alkane is ‘-ane’. It is stable so doesn’t react under normal conditions. Hence, it is also called paraffins.

First four homologues of alkane are:

Methane (CH₃)
Ethane (CH₂CH₃)
Propane (CH₂CH₂CH₃)
Butane (CH₂CH₂CH₂CH₃)

Methane

Methane (CH4) is the simplest and a saturated hydrocarbon. It is called alkane because it has only a single covalent bond. It is found in marshy places so, it is also called marshy gas.

Some uses of Methane gas are:

It is used as fuel in LNG (Liquified Natural Gas).

Alkene

Alkene is an unsaturated hydrocarbon containing at least one double bond between the joining carbon atoms. It is represented by a general formula C_nH_2n. The suffix for alkene is ‘-ene’.

First four homologues of alkene are:

Ethene (C₂H₄)
Propene (CH₂C₂H₄)
Butene (CH₂CH₂C₂H₄)
Pentene (CH₂CH₂CH₂C₂H₄)

Alkyne

Alkyne is an unsaturated hydrocarbon containing at least one tripple bond between the joining carbon atoms. It is represented by a general formula C_nH_2n-2. The suffix for alkyne is ‘-yne’.

First four homolgues of alkyne are:

Ethyne (C₂H₂)
Propyne (CH₂C₂H₂)
Butyne (CH₂CH₂C₂H₂)
Pentyne (CH₂CH₂CH₂C₂H₂)

Alcohol

Organic compounds containing hydroxyl (OH) group as their primary functional groups are called alochol organic compounds. Organic compounds formed by displacing hydrogen of an alkyl group are called alcohol.