Questions

A pure substance can be defined as any single type of material that has not been contaminated by another substance. In chemistry, a pure substance has a definite composition. It can be a compound or an element. A pure substance is considered to be a material that consists of one type of "building block" of matter.

Examples of pure substances include tin, sulfur, diamond, water, pure sugar (sucrose), table salt (sodium chloride) and baking soda (sodium bicarbonate).

Tin, sulfur, and diamond are examples of pure substances which are chemical elements. All elements are pure substances.

Water, sugar, salt and baking soda are pure substances which are chemical compounds. Chemical compounds also are pure substances

The Mediterranean sea separates Europe from Africa.

Ethiopia is the new name of a country which is historically called as Abyssinia.

New name     -      Old name

Namibia        -      South West Africa

Zimbabwe     -      Southern Rhodesia

Thailand        -      Siam.

Grey Revolution is associated with Fertilizers.

• Cotton - Silver fiber Revolution

• Fruits - Golden Revolution

• Oil seeds - Yellow Revolution