Rocks, Minral and metals for std 8 to 10 science CBSE

Rocks, Minerals and Metals

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Rocks, Minerals and Metals

Rocks are found on the crust of the earth and made up of mineral.

Coarse grained Granite.

Some are coarse grained as granite. Clay has much fine grains that we cannot see them separately. If you closely examine a piece of granite, you will find that it is made up of a number of substances under a magnifying lens or a microscope. Substances which assemble together to form rocks are called minerals. Minerals are naturally occurring inorganic substances.

The earth Crust

Remainder of the crust consists of mainly six metals (1) Aluminum (most abundant) (2) Iron (3) Calcium (4) Sodium (5) Potassium (6) Magnesium.

Three forth of the earth crust is made just of two non metals. 

(1) Oxygen (2) Silicon.

The average thickness of earth crust is 35 km under the continents and 10 km under the oceans.

Different types of Rocks

Igneous rocks

Meaning:- Word derived from the latin word ‘ignis’ meaning fire. First rock to appear on the earth’s surface.

Formation:- Formed by the cooling and solidification of extremely hot molten material, magma below the earth crust. This magma pushes its way through earth’s crust with high pressure to form igneous rocks.

Sedimentary Rocks

By the deposition for sediments SEDIMENTS are broken down particles of existing rocks which are deposited layers by layers by flowing water or wind in the sea along with dead plants and animals.

All this are neatly preserved in the sediments.

The process goes on for millions of years and the resultant rocks are called Sedimentary rocks. 

 Sedimentary rocks contains the relics of plants & animal known as Fossils.

They harden with age. 

Thickness of overlaying layers are usually soft.

Metamorphic rocks

FORMATION :- When igneous or sedimentary rocks are subjected to intense heat, compression or fluid injection the physical & chemical properties changes which results in metamorphic rock.

Minerals : 

1. Naturally occuring inorganic substances with specific composition.
2. Substance which assemble together to form rocks are called Minerals. There are about 2000 distinctive minerals.
3. A mineral made of atom of a single element or of more than one elements.
4. It is identified by its physical properties such as colour, lustre, hardness, specific gravity and cleavage.

Types of Minerals

Minerals and their uses

Identifu uses of Minerals

Common Ores

Blast Furnace 

Blast Furnace

The concentrated ore along with coke (c) and limestone are added to a blast furnace. Blasts of hot air at about 19000 C are blown into the furnace lined with fire bricks. The coke reduces the ore to metallic iron. The molten iron collects at the bottom of the furnace. Limestone on heating decomposes to calcium oxide and carbon dioxide. Calcium oxide reacts with the sand and forms a slag (calcium silicate).

Pig iron and Wrought iron difference.