Chemistry/Physics - GCSE

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  • Created by: HansleyR
  • Created on: 27-06-17 17:41

Science Revision

 

Rocks

Rocks are made from grains that fit together. Some types of rock have inter-locking grains that fit tightly together. Granite is a rock with inter-locking grains. Other types of rocks have rounded grains, (sandstone).

Porous Rocks

Rocks with round grains are more likely to absorb water than rocks with inter-locking grains. This is because the water cannot get into the gaps between the grains. Rocks that absorbs water are called porous. Rocks with inter0locking grains are more likely to be hard and non-porous.

Sedimentary Rock

Formation:

A river carries or transports pieces of broken rock as it flows along. When the river reaches a lake or the sea, its load of transported rocks settles to the bottom. We say that the rocks have been deposited. The deposition of the rocks build up layers, called sediments, this process is called sedimentation. The water is squeezed out from between the pieces of rocks and crystals of different salts form. The crystals form a sort of glue that sticks or cements the piece of rocks together. This process is called cementation. These process eventually make a type of rock called sedimentary rock. These are different process in order: Sedimentation, compaction, cementation. Limestone, chalk, sandstone, shale may contain fossils.

Igneous Rock

Formation:

The inside of the earth is very hot- hot enough to melt rocks. Molten (liquid) rock forms when rocks melt. The molten rock is called magma. When the magma cools, it solidifies, a type of rock called igneous rock is formed. Igneous rocks contains inter-locking crystals. The size of the crystals depends on how quickly the molten magma solidifies. Obsidian is naturally occurring volcanic glass formed as an igneous rock. Gabbro is an igneous rock.

Crystal size

Igneous rocks contain interlocking crystals. The size of the crystals depends on how quickly the molten rock cooled:

If it cooled quickly, the crystals are small

If it cooled slowly, the crystals are large

The slower the molten rock cools, the larger the crystals in the igneous rock. Igneous rocks are made when molten rock cools down and solidifies.

 

 

 

Metamorphic Rock

They are formed from other rocks because of heat or pressure.

Formation:

Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under pressure, they don’t melt, but the minerals they contain are changed chemically, forming metamorphic rocks. Metamorphic rocks are formed when rocks are close to molten magma.                                                                 Examples: marble, slate, granite

Weathering

Rocks gradually wear away (weathering). It is a process when rocks is dissolved into smaller pieces. Three types of weathering: biological, chemical, physical.

 

Physical Weathering

This is caused by physical changes such as: temperature effects of the winds, rain and waves. Another type of physical weathering is freeze-thaw. Freeze-thaw is when water gets into a rock it freezes or expands because cold water expands. When a rock gets hot it expands a little, and when it gets cold the rock…

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