Some rocks are harder than others. For example, granite is a very hard rock, but chalk is a very soft rock and wears away easily.Some rocks, such as sandstone or chalk, let water soak through them. They are called permeable rocks.Other rocks, such as marble and slate, do not let water soak through them. They are called impermeable rocks.

Uses of Rocks

1.Slate-Because slate is a hard, impermeable rock, which splits easily into thin sheets, it is ideal for making roofing tiles.

2.Marble-has an attractive texture and colour and can be cut and polished. Because of this, it is used to make floor tiles and wall tiles. Some statues are made from marble too.

3.Chalk-is a rock that is formed from the skeletons of tiny sea animals. It wears away very easily which is why it ideal for making sticks of chalk to write on blackboards.

4.Granite-is a coarse-grained rock that is hard and impermeable. It is often used to make steps and roads as it is a rock that doesn�t wear away easily.

Classification of Rocks

Deep in the centre of the Earth, under the Earth's crust, it is so hot that some rocks melt. The melted rock is called magma.

When a volcano erupts it forces magma to the suface of the Earth. Now it is called lava As it gets nearer to the Earth's surface the lava cools and hardens to form rock.

This type of rock is called igneous rock.

Granite, pumice and basalt are all igneous rocks.

Sedimentary Rocks are formed from tiny particles of sand or clay, or animal or plant remains.

Rivers wash these tiny particles out into the sea or lakewhere they settle on the sea bed.

Over millions of years the layers at the bottom of the lakes and seas are crushed by the new layers and the water above them and form a band of new rock.

Chalk, limestone, sandstone and shale are all sementary rocks.

Metamorphic rocks are formed when buried rock is pressed or squeezed by forces inside the Earth. The pressed rock gets very hot.

Sometimes the heat and pressure is so great that the rocks are melted and turned into totally different rocks.

These new rocks are called metamorphic rocks. They are usually much harder than the original rocks.

Marble and slate are metamorphic rocks.

ACTIVITY:

1.Collect different kind of rocks and identify where classification do they belong.

2.Put different rocks together to form a pyramid and identify all rocks that were used.

3.Observe around our environment and list the uses of rocks in your daily life.

4.Try different types of activities available below.