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. .