Class 10 Science Carbon and Its Compound Exam Notes

Class 10 Science Carbon and Its Compound Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Introduction

Carbon is most important element because it forms largest number of compounds which are useful in our daily life. In this chapter, we shall study about carbon and its compounds.

Important Terms and Concepts :

Carbon : Its atomic number is 6. Its mass number is 1.20. Its atomic mass is 12.011. Its melting point is 3550ºC and boiling point is 4830ºC. It occurs in free state as well as in combined state. 70% of our body is made up of carbon. It forms largest number of compounds. The earth crust contains only 0.02% of carbon.

Organic Compounds : Those compounds which consist of carbon essentially and hydrogen mostly along with other elements like oxygen, sulphur, nitrogen, halogens, etc. are called organic compounds.

Coal :  It is a naturally occurring solid fuel which exists in the form of varying depths below the earth’s surface. It is formed by decay of vegetation that grew 40 to 300 million years ago, followed by chemical processes of condensation and polymerization under influence of temperature, pressure and time.  

Petroleum :  It is an oil found in rocks. It is a mixture of solid, liquid and gaseous hydrocarbons. It is a source of petrol, diesel, kerosene, petroleum ether, petroleum coke, petroleum wax, etc.

Carbonates :  They are compounds of carbonic acid. They are found in earth crust, e.g., CaCO₃, MgCO₃, Na₂CO₃, Na₂CO₃, ZnCO₃. They are thermally stable.

Hydrogen Carbonates :  They contain HCO₃^– ions. They are formed by replacing one H⁺ of carbonic acid, e.g., NaHCO₃, Ca(HCO₃)₂, Mg(HCO₃)₂. They are soluble in water. They are thermally unstable, i.e., decompose on heating to form carbonates, CO₂ and H₂O.

Chemical Bond :  It is a force of attraction which holds the two atoms together.

Covalent Bond :  It is the bond formed by equal sharing of electrons, e.g., Hydrogen has one valence electron. It can share one valence electron with other hydrogen atom to form H₂ molecule so as to acquire nearest noble gas configuration. The bond between two hydrogen atoms by sharing one electron each is called covalent bond.

Covalency of Carbon :  Carbon has four valence electrons. It cannot lose four electrons since very high amount of energy will be required to lose four electrons to form C⁴⁺ ion. There is strong force of attraction between nucleus and valence electrons.

Carbon cannot gain four electrons to form C^4– ion because six protons cannot hold 10 electrons easily and there will be strong interelectronic repulsion.

Carbon can share four electrons easily with other atoms of carbon and other elements to acquire stable electronic configuration.

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