Physical and Chemical Properties of Metals : Science NCERT / CBSE Revision Notes
Metals are strong and durable. That’s why metals are used so widely for making almost everything. For example metals are used in making machinery, automobiles, aeroplanes, buildings, trains, satellites, gadgets, cooking utensils, water boilers, etc.
However not all metals are hard, strong and durable solids. Sodium and potassium are soft metals that can be cut with a knife. Mercury is a liquid metal.
Physical Properties of Metals:
- The metal base in an electric iron is for conducting heat, not electricity. Metals are very good conductors of heat, too. That’s why cooking utensils, irons, heaters, etc. are all made of metals.
- Metals can be easily shaped into wires. This property of metals is called ductility.
- Metals can be easily shaped into thin flat sheets. This characteristic of metals is called malleability.
- Metals make a sound when struck with hard objects. Metals can be polished to a shiny appearance. That’s why gold and silver jewellery shine so much.
Chemical Properties of Metals:
- Iron reacts with atmospheric oxygen and moisture to form iron oxide, which is commonly known as rust. Metals burn in the presence of oxygen to form metal oxides, which are basic in nature. For example, if you burn a strip of magnesium, magnesium will burn in oxygen to form magnesium oxide.
- Magnesium oxide dissolves in water to form magnesium hydroxide, which is basic in nature.
- When a copper vessel is exposed to moist air, a green coating forms on its surface. The coating is a mixture of copper hydroxide and copper carbonate.
- Nails rust because of the moisture present in air.
- Sodium reacts vigorously with water and oxygen, and produces so much heat that it catches fire! That’s why sodium is stored in kerosene - to prevent it from coming into contact with moisture and oxygen.
- Red litmus paper turns blue in solutions basic in nature. Lime juice contains citric acid. Acids react with salts of metals.
- Metals react with acids, such as hydrochloric acid and sulphuric acid, to give out hydrogen gas.
- Copper does not react with dilute hydrochloric acid even on heating, but it reacts with dilute sulphuric acid on heating.
- Metals react with bases, such as sodium hydroxide to produce hydrogen gas.
- Different metals react differently. More reactive metals can displace the less reactive metals in a compound during reactions. For example, sodium reacts more vigorously than others when it comes in contact with air.