Chemistry Revision (C1)

Front 1

THE EARLY ATMOSPHERE

Back 1

The Earth's first atmosphere was formed by gases produced by volcanoes. It contained large amounts of carbon dioxide and water vapour, hardly any oxygen and small amounts of other gases. The Earth was very hot to start with, and there were no oceans. As the Earth cooled down the water vapour in the atmosphere condensed to form liquid water. This liquid water became the oceans.

ADDING OXYGEN:
Earth cools and oceans form. Forms of life evolve in the oceans and photosynthesis begins. Oxygen builds up in the oceans. Oxygen builds up in the atmosphere.
REMOVING CARBON DIOXIDE:
Carbon dioxide dissolved in the oceans. Marine organisms used the dissolved carbon dioxide to make calcium carbonate for shells. The shells of dead marine organisms fall to the sea bed and become part of the sediment. Over millions of years the layers of sediment become squashed to form sedimentary rocks.

Front 2

A CHANGING ATMOSPHERE

Back 2

The amounts of different gases in the atmosphere are shown below. The atmosphere also contains water vapour but this is not usually included because the amount changes depending on the weather.
Nitrogen - 78%
Oxygen - 21%
Argon - 0.9%
Carbon Dioxide - 0.04%
traces of other gases

Front 3

ROCKS AND THEIR FORMATION

Back 3

Rocks make up the Earth's crust.
IGNEOUS ROCKS:
> Are formed when magma or lava solidifies
> Are made of interlocking crystals, which makes them hard and resistant to erosion
> Have small crystals if the liquid rock cooled quickly (e.g. Basalt)
> Have large crystals if the liquid rock cooled slowly (e.g. Granite)
SEDIMENTARY ROCKS:
> Are formed when layers of sediment are compacted (sqaushed together) over a very long time by being buried under more layers
> Erode (wear away) more easily than igneous and metamorphic rocks
> Are made of rounded grains and may contain fossils (the remains or traces of living organisms)
> Include chalk and limestone, which are natural forms of calcium carbonate
METAMORPHIC ROCKS:
Metamorphic rocks are formed from existing rocks by the action of heat (being buried on or near magma) and/or pressure (from being buried), which causes new interlocking crystals to grow. Marble is a metamorphic rock which is formed from chalk or limestone (both sedimentary rocks)