Evolution of the atmopshere
The Earth's surface was molten for millions of years. When things cooled down a thin crust was formed but volcanoes still erupted giving out Carbon Dioxide and water vapur, The water vapour then condensed to form oceans. Most of the Carbon Dioxide dissolved into the sea and was taken in by marine life. When the microorganisms died they became buried under layers of sediment and the carbon dioxide was locked up in carbonate rocks, when green plants evolved thet reoved carbon dioxide from the atmosphere for photosynthesis. This caused oxygen levels to be increased. The increasing oxygen levels killed of some microorganisms but allowed more complex microorganisms to develop there is vey little Carbon dioxide left.
Humans are causing the atmosphere to change by: burning fossil fuels which releases carbon dioxide. Deforestation: tree's remove carbon dioxide from the air with less tree's less carbon dioxide is removed. Livestock farming produces lots of methane.
Volcanic activity is also changing the atmosphere as it releases sulphur dioxide and carbon dioxide.
Investigating the proportion of oxygen
This experiment shows that the air is one fifth oxygen.
Heat an excess of copper in atube and pass air over it with two syringes. you can use the markers to see how much oxygen has been used up. Make sure the system is sealed so no air can escape or get in. If you start with 100cm you will end up with around 80cm . If 20cm has gone the air is 20% oxygen. The chemical equation for this reaction is:
Sedimentary rocks formed from layers of sediment at the bottom of lakes or sea's (sedmentation)the layers increased squashing the sediment at the bottom (compaction) water squeezes outand crystals of differnt salts form which cement the rock together (cementation). Limestone and chalk are sedimentary rocks and often contain fossils.
Metamorphic rock is formed by heat and pressure on sedimentary rocks overlong periods of time. As long as they don't melt they are classed as metamorphic. Marble is formed from limestone or chalk
Igneous rocks are formed when molten magma is pushed up into the crust before cooling and solidifying. EXTRUSIVE rocks cool QUICKLY ABOVE GROUND forming SMALL crystals. INTRUSIVE rocks cool SLOWLY UNDERGROUND forming LARGE crystals. Granite and baslat are igneous rocks.
Limestone is a building material
Limestone is a grey/white colour and is quarried out of the ground. It is great for building with as it is virtually insoluble in water but dissolves in acid rain. It can be crushed up into chippngs and used for road surfacing.
Limestone for other things.
Limestone is the raw material to make other building materials. Powdered limestone is heated in a kiln with powdered clay to form cement, this can be mixed with sand, gravel and water to frm concrete. You can also make glass by heating limestone with sand and water until melts.
Disadvantages of Quarrying limestone
Quarrying limestone can cause environmental problems it makes large unsightly holes in the landscpes and thq quarrying process creates lots of noise and dust in quiet areas. It can destroy animals and birds habitats. The lorries needed to transport the limestone also cause traffic.
Advantages of Quarrying
Limestone provides people things people want such as houses, roads and chemical used from limestone in medicine. Limestone neutralises acidic soil and sulphur dioxide (sulphur dioxide causes acid rain). It also provides jobs.
Limestone is mainly Calcium Carbonate ( ). When it's heated it thermally decomposes to make calcium oxide and carbon dioxide.
Calcium Carbonate ---> Calcuim Oxide + Carbon Dioxide.
Copper Carbonate ---> Copper Oxide + Carbon Dioxide.
Zinc Carbonate ---> Zinc Oxide + Carbon dioxide.
less stable carbonates decompose faster and turn limewater cloudy quicker.
sometimes there is a colour change e.g copper carbonate - Green and copper oxide - Black
Atoms and mass in chemical reactions
Elements and compounds made up of atoms ( smallest particles). The atoms take part in the chemical reactions. The atoms dont appear and disappear they are just rearranged in different ways to give new products. Magnesium + Oxygen ---> Magnesium Oxide
Because the atoms are not gained or lost the mass of reactants equals the mass of products.
If you do a reaction in a sealed container the total mass doesn't change. You can show this in a precipitaion reaction. A precipitation reaction happens when two solutions react to form an insoluble solid. Copper Sulphate + Sodium Hydroxide --> Copper Hydroxide + Sodium Sulphate
Nothing has escaped from the flask to mass at the start and end of the experiment are the same.