Revision: Chemistry in Everyday Life Science SSLC (English Medium) Class 8 Tamil Nadu Board of Secondary Education

Saturated hydrocarbons (containing a single bond) are called ‘Alkanes’.

Hydrocarbons are compounds that 9re made up only of carbon and hydrogen atoms.

OR

The compounds which contain carbon and hydrogen as the only two elements are called hydrocarbons.

Saturated hydrocarbons are hydrocarbons in which the valencies of all atoms are satisfied by single bonds.

The unsaturated hydrocarbons containing a carbon-carbon double bond are called ‘Alkenes’.

The unsaturated hydrocarbons whose structures contain a carbon-carbon triple bond are called ‘Alkynes’.

The hydrocarbons that have double or triple covalent bonds between two adjacent carbon atoms are called unsaturated hydrocarbons.

OR

The carbon compounds having a double bond or triple bond between two carbon atoms are called unsaturated compounds. Ethene and ethyne are unsaturated hydrocarbons.

• Hydrocarbons contain only carbon and hydrogen atoms and are the basic type of organic compounds.
• Saturated hydrocarbons have single bonds (e.g. methane, ethane, propane).
• Unsaturated hydrocarbons have double or triple bonds (e.g. ethene, ethyne).
• To draw structures, join the carbon atoms first, then add hydrogen atoms to complete 4 bonds per carbon.
• Ethene has a double bond, and ethyne has a triple bond between carbon atoms.

• Natural gas is a fossil fuel found along with petroleum and mainly consists of methane (about 95%).
• It is used in different forms such as LPG (cooking gas), CNG (vehicle fuel) and PNG (piped gas for homes).
• Mumbai High is the largest producer of natural gas in India; other producing areas include Assam, Gujarat, Andhra Pradesh, Rajasthan, Tripura and Tamil Nadu.
• Natural gas is a cleaner and eco-friendly fuel as it emits less carbon dioxide and leaves no solid residue.
• It is non-renewable, highly inflammable, and requires costly infrastructure for extraction, storage and transport.