th Class 8 (Chemistry) Chp 9 Carbon and its Compound
Occurrence of Carbon:
Carbon occurs in nature in Free State (as element) as well as in combined state (in the form of compounds with other elements).
In free state carbon occurs in nature mainly in two forms diamond and graphite.
In the combined state carbon occurs in nature in the form of compounds such as (i) carbon dioxide gas in air, (ii) carbonates like limestone, marble and chalk, (iii) fossil fuels like coal petroleum and natural gas, (iv) organic compounds like carbohydrates, fats and proteins and (v) wood, cotton and wool etc.
Q. Write about the occurrence of carbon.
All the carbon compounds are classified into two classes:
1. Organic compounds
2. Inorganic compounds
Names of some carbon compounds:
Organic compounds:
Class Name Chemical formulae
Hydrocarbon Methane CH4
Butane C4H10
Ethene C2H4
Ethyne C2H2
Benzene C6H6 Naphthalene C10H8
Alcohols Methyl alcohol CH3OH
Ethyl alcohol C2H5OH
Acids Acetic acid (vinegar) CH3COOH
Formic acid HCOOH
Oxalic acid (COOH)2
Sugars Glucose C6H12O6
Sucrose C12H22O11
Inorganic compounds:
Name Chemical formula
Carbon dioxide CO2
Carbon monoxide CO
Calcium carbonate CaCO3
Sodium carbonate Na2CO3
Copper carbonate CuCO3
Zinc carbonate ZnCO3
Sodium bicarbonate NaHCO3
Calcium bicarbonate Ca(HCO3)2
The large number of organic compound is due to the ability of carbon atom to form long chain with another carbon atom through sharing of electrons. This is a unique property of carbon known as catenation. Q. Give 4 examples of each: 1. Organic compound 2. Inorganic compound Q. What is catenation?
Some useful carbon products:
Plastic
Properties:
1. Plastic is flexible. 2. It is a bad conductor of electricity. 3. Melts on heating. It catches fire. 4. Can be moulded into various shapes.
Ceramic
Properties:
1. Ceramic is shiny and smooth. 2. It is hard and brittle. 3. It is a good conductor of heat and poor conductor of electricity. 4. Ceramic is not transparent.
Glass
Properties:
1. Class is shiny, smooth and hard. 2. Glass is hard but when heated, it can be moulded into any shape. 3. It is brittle. 4. Is a good conductor of heat and poor conductor of electricity. 5. Class can be used as mirror which reflects light.
Q. Name some useful carbon products.