Class 9 Science Note
Elements are basically divided into three groups:
Physical Properties of metals
They are malleable and ductile.
They are good conductor of heat and electricity.
They have high melting and boiling point.
They are found in solid state at normal temperature except for mercury.
They possess metallic luster.
Chemical properties of metals
Metals react with oxygen to form basic oxides.
2Na + O2→ 2NaO
Metals form salt and gas when reacting with acids.
Zn + 2HCl → ZnCl2 + H2
When hydrogen is passed through metals like copper, sodium potassium hydride is formed.
Ca +H2 Ø CaH2
CARBON AND ITS COMPOUNDS
Carbon is a chemical elementwith symbol C and atomic number 6. As a member of grou 14 on the periodic table, it is nonmetallic and tetravalentmaking four electrons available to form covalentchemical bonds.
Carbon is found in the form of compounds except in diamond, graphite, coal etc. which are obtained freely in nature. Some of the main sources of carbon are as follows:
a. In air, carbon dioxide is found.
b. Various petroleum products
c. In all living organisms, in substances like carbohydrate, starch, urea etc.
Carbon forms the covalent bond by sharing an electron with other element. It can combine with other carbon atom to form a long chain carbons form chainwhich is called catenation
Then carbon is heated with oxygen, and then carbon dioxide gas is formed.
C + O2 Ø CO2
When carbon is heated with less oxygen, then carbon monoxide is formed.
2C + O2 Ø 2CO
When carbon is heated with lead oxide, then carbon dioxide is given out.
C + 2PbO Ø CO2 + 2Pb
When carbon is heated with water vapor, then carbon monoxide and hydrogen gas are formed.
C + H2O Ø CO + H2