C2- CHEMICAL RESOURCES

HideShow resource information

C2- CHEMICAL RESOURCES

1 of 20

The Earth's Structure

(http://www.bbc.co.uk/staticarchive/18e0518ed5183cd531f908f11031e176c4461b9c.gif)

2 of 20

The Earth's Structure

The crust- thin layer of solid rock (a depth of 20km)

The lithosphere- includes the crust and the upper part of the mantle. It's made up of a jigsaw of tectonic plates and is relatively cold and rigid (over 100km deep in places)

The mantle- solid section between the crust and core. Near the crust it is very rigid, however as it gets closer to the core it gets heated and can begin to turn into a liquid.

The core- just over half the earth's radius. The inner core is solid, while the outer core is liquid.

Radioactive decay causes a lot of heat inside the earth. The heat creats convection currents in the mantle, causes the plates of the lithosphere to move.

3 of 20

The Earth's Structure

Tectonic plates- big rock plates that float on the mantle (they're less dense than it). They move at about 2.5cm per year. Volcanoes and earthquakes often occur where the plates meet. It's the movement of the plates against each other that causes them.

Seismic waves- tell us what's below the crust. These waves are produced by earthquakes or big man-made explosions. By measuring the time it takes the waves to travel, and where they are detected, scientists can draw conclusions about the Earth's structure. 

P-waves travel through solids and liquids. S-waves travel through solids.

4 of 20

Plate Tectonics

Fossils- plant and animal fossils have been found on opposite sides of the Atlantic Ocean. Explaining this was hard work, and in 1914, Alfred Wegener had a theory that Africa and South America had once been one continent. To back this up, he also found that there were matching layers in the rocks on both continents, and similar earthworms living in both areas. 

Continental drift- His theory was that 300 million years ago there was one 'super' continent called "Pangaea". According to his hypothesis, it broke into smaller chunks which then drifted apart and continue to drift in he present day- it's similar to our recent theory of plate tectonics. The theory wasn't accepted at first, it made the 'land bridge' idea wrong, and scientists did not trust his new theory. The main problem was his unconvincing idea about how they drifted apart. He thought they could be caused by tidal forces and rotation of the Earth.

1960- Scientists investigated the Mid-Atlantic Ridge, they found magma rises through the sea floor, solidifies and forms mountains underwater, similar each side of the ridge. This suggested that the sea floor was spreading (at about 10cm per year). 

The magnetic orientation gave good evidence, as magma rises, iron particles align themselves with earth's magnetic field, as it cools they set. When the field swaps direction, rocks either side of the ridge has bands of alternative magnetic polarity, symmetrical about the ridge. This proved new sea floor was being created, and continents moving apart- Wegener's theory was supported.

5 of 20

Volcanic Eruptions

Volcanoes- formed by molten rock from the mantle when it emerges through the Earth's crust. 

Oceanic and Continental crust colliding causes volcanoes- the crust at the ocean floor is denser than than the crust below the continents. When the plates collide, an oceanic plate is forced under a continental crust. Oceanic is also cooler at the edges, so edges sink easily, pulling the oceanic plate down. As the oceanic crust is forced down it melts and starts to rise, if molten rock finds it's way to the surface, volcanoes form.

Igneous rock

Igneous rock is made when any sort of molten rock cools and solidifies. The type of rock depends on how quickly it cools and composition of the magma. Some volcanoes produce iron-rich basalt, lava from the eruption is runny and the eruption is fairly safe. If the magma is silica-rich rhyolite, the eruption is explosive. It produces thick lava.

To predict, geologists track magma movement, which can mean that they can predict with greater accuracy. Volcaanoes are unpredictable though and predictions are only estimates.

6 of 20

Different Types of Rock

Sedimentary- formed from layers of sediment laid down in lakes or seas. Over millions of years, the layers get buried under more and the weight squeezes out the water. These fluids deposit natural mineral cement.

Limestone- formed from seashells. It's mostly calcium cabonate and grey/white in colour. When thermally decomposed it makes calcium oxide and carbon dioxide. CaCO3(s) --> CaO(s) + CO2(g)

Metamorphic- formed by action of heat and pressure on sedimentary and sometimes igneous rock over long periods of time.  The mineral structure and texture is different, but chemical composition is the same. As long as they don't melt they're labelled as metamorphic, if melted, they can resurface as igneous.

Marble- metamorphic formed from limestone, high temperatures and pressures break down the calcium carbonate and it reforms as small crystals, gives it an even texture and makes it much harder.

Igneous- formed from fresh magma cooling. They contain various different minerals in randomly arranged interlocking crystals, making them very hard. 

Granite- a very hard igneous rock, ideal for steps and buildings.

7 of 20

Construction Materials

Aluminium and Iron- extracted from ores in rocks (ores are minerals we can get useful materials from). Aluminium and iron are construction materials that can be extracted from their ores.

Glass- melting limestone (calcium carbonate), sand (silicon dioxide) and soda (sodium carbonate). When the mixture cools it comes out as glass.

Bricks- made from clay (weathered and decomposed rock). It's soft when dug up, making it easier to mould into bricks. When fired at high temeratures, it hardens so can withstand weight of more bricks on top of it.

Limestone and Clay- they are heated to make cement. Clay contains aluminium and silicates, powdered clay and powdered limstone are roasted in a rotating kiln to make a mix of calcium and aluminium silicates, cement. When mixed with water, a slow reaction takes place to make it set hard slowly. When mixed with sand, aggregate and water it makes concrete. Steel can be added.

Environmental Damage- quarrying uses up land and destroys habitats- costs mooney to improve the area again. Transporting rock cuase noise and pollution. Quarrying causes dust and is noisy. Disused sites are dangerous- people drown, and disused mines can collapse and cause subsidence.

8 of 20

Extracting Pure Copper

Electrolysis- passing a current through impure copper splits the pure off from impurities. Copper is immersed in liquid (electrolyte) which can conduct electricity. Electrolytes are normally free ions dissolved in water, Copper(II) sulfate solution is used as an electrolyte, contains CU2+ ions.

The electrical supply acts as an electron pump-

1. It pulls electrons off copper atoms at the anode, causing them to go into solution as CU2+ ions.

2. It offers electrons at the cathode to nearby CU2+ ions to turn them back into copper atoms.

3. The impurities are dropped at the anode as a sludge, whilst pure copper atoms bond to the cathode.

During electrolysis, copper dissolves away from the anode and is deposited at the cathode. The anode loses mass and the cathode gains mass.

Recycling Copper- saves money and resources.

It's cheaper to recycle than mine and extract new copper from ores. It only uses 15% of the energy that mining and extracting would. Recycling takes time and energy- people don't like this.

9 of 20

Extracting Pure Copper

(http://www.oocities.org/vdkh13/chap5_files/image008.gif)

Reaction at Cathode- Cu2+(aq) + 2e- --> Cu(s)  REDUCTION is gain of electrons/ removal of oxygen

Reaction at Anode- Cu(s) --> Cu2+(aq) + 2e-  OXIDATION is loss of electrons/ gain of oxygen

The cathode is the negative electrode. It starts thin and more adds to it throughout the reaction. The anode is the positive electrode. It starts as a big lump but dissolves.

10 of 20

Alloys

Alloy- is a mixture of a metal and other elements. They can be a mixture of two or more metals, can also be a mixture of a metal and non-metal. Often have properties different from the metals that make them, new ones can make them more useful.

Steel- alloy of iron and carbon. It's harder than iron and stronger too. Iron on it's own will rust quickly, whereas steel is less likely to. Steel is used to make a lot of stuff- bridges, engines, cutlery, saucepans, ships, drill bits and cars.

Brass- copper and zinc, brass is harder than both, used for instruments and fixings.

Bronze- copper and tin, harder and stronger than tin, more resistant to corrosion than both. Used for springs, motor bearings, bells and used in sculptures.

Solder- lead and tin, no definite melting point. Used to solder things together.

Amalgam- alloy containing mercury, used in dentistry for filling teeth.

Smart Alloys- Nitinol is a family of alloys of nickel and titanium and have shape memory. They remember their original shape even after being misshapen. this is useful for things such as glasses, they can be bent or sat on and still go back to their original shape.

11 of 20

Building Cars

Iron and Steel corrode much more than Aluminium. Iron only rusts when in contact with water and oxygen- it's an oxidation reaction. Iron gains oxygen to form Iron(III) oxide. Water then bonds loosely to the iron oxide and forms hydrated Iron(III) oxide- or rust.

Iron + oxygen + water --> hydrated iron(III) oxide

Car bodies- Aluminium or steel? Aluminium has a lower density (better fuel economy) and it also corrodes less than steel (car bodies will last longer). However, it is much more expensive than iron or steel, hence manufacturers tend to use steel anyway.

Steel is good for bodywork as it can be hammered into different shapes, aluminium is strong and has a low density so is used for engine parts to reduce weight, glass is used for windows and windscreens as it's transparent, plastics are light and hardwearing which makes them good for internal covering, fibres are hardwearing, meaning they're used to cover seats and floors.

Recycling- save natural resources, money and reduce landfill. Metal from cars is quite often recycled, through most other materials go into landfill. European laws are now in place to say that 85% of car materials have to be recycled, and this is rising to 95%. The materials have to be seperated to be recycled, making it difficult and time consuming.

12 of 20

Acids and Bases

(http://0.static.wix.com/media/19bd7d_1904e949c30a03f627e1aea21f54bdd6.jpg_1024)

13 of 20

Acids and Bases

Universal Indicator- a dye that changes colour. The dye changes colour depending on the pH of a substance, making it a good estimator of pH value. It goes from 0 to 14, strong alkali is 14, strong acid is 0, neutral is 7.

Acids and Bases neutralise each other.

An acid is a substance with pH7 or below. They form H+ ions in water, the pH of an acid is determined by the concentration of the H+ ions.

A base is a substance with a pH bigger than 7. An alkali is a base that is soluble in water. Alkalis form OH- ions in water.

The reaction between acids and bases is called neutralisation- acid + base --> salt + water

They can also be in terms of ions- H+ + OH- <--> H2O (the <--> sign means it's reversible)

When an acid neutralises a base or vise versa, the products are neutral with pH7.

14 of 20

Reactions of Acids

Metal oxides and metal hydroxides can dissolve in water. These soluble compounds are alkalis. Bases that won't dissolve in water will still react with acids. All metal oxides and metal hydroxides react with acids to form a salt and water. Acid + Metal oxide --> salt + water or acid + metal hydroxide --> salt + water.

Hydrochloric acid + copper oxide --> copper chloride + water

Sulfuric acid + potassium hydroxide --> potassium sulfate + water

Nitric acid + sodium hydroxide --> sodium nitrate + water

Phosphoric acid + sodium hydroxide --> sodium phosphate + water

Acids and carbonates produce carbon dioxide- acid + carbonate --> salt + water + carbon dioxide

Hydrochloric acid + sodium carbonate --> sodium chloride + water + carbon dioxide

Sulfuric acid + calcium carbonate --> calcium sulfate + water + carbon dioxide

Phosphoric acid + sodium carbonate --> sodium phosphate + water + carbon dioxide


15 of 20

Reactions of Acids

Acids and Ammonia produce Ammonium Salts

Acid + Ammonia --> Ammonium salt

Hydrochloric acid + ammonia --> ammonium chloride

Sulfuric acid + ammonia --> ammonium sulfate

Nitric acid + ammonia --> ammonium nitrate

Ammonium nitrate is also known as fertiliser.

16 of 20

Fertilisers

Fertilisers provide plants with essential elements for growth:

The three main elements in fertilisers are nitrogen, phosphorus and potassium. If plants don't get enough of these their growth and life processes are affected. These elements can be used up if the soil had previously had a different crop in it, and fertilisers replace the missing elements or provide more of them. This helps increase crop yield as they grow faster and bigger. The fertiliser must dissolve in water before being taken in by plant roots.

Ammonia can be neutralised with acids to produce fertiliser. Ammonia is a base and can be neutralised with accids to form ammonium salts. Ammonia is a key ingredient in many fertilisers. Most common is ammonium nitrate- has nitrogen from two sources. Ammonium sulfate, ammonium phosphate and potassium nitrate can aso be used. 

They are really useful, however can cause big problems-

The population of the world is rising, fertilisers increase crop yield, so the more fertiliser we make, the more crops we can grow and the more people we can feed. But if we use too many, we risk  polluting our water supplies and causing eutrophication.

17 of 20

Eutrophication

(http://cwh.triplepointwater.com/app/webroot/img/ckfiles/images/eutrophication.jpg)

18 of 20

Preparing Fertilisers

Preparing Ammonium nitrate in the lab- you can make most fertilisers using this titration method:

1. You would put acid in the burette and ammonia and methyl orange in the conical flask.

2. Then add nitric acid slowly, swirling constantly. The mixture should turn from orange to red once all of the ammonia has been neutralised to make ammonium nitrate solution.

3. To get solid ammonium nitrate you would evaporate most of the liquid, only leaving little and then leaving it to crystalise.

4. But these are not pure as they have some methyl orange in them so you have to note exactly how much acid was needed and repeat without using the methyl orange.

Percentage yield

Percentage yield compares the actual yield to the predicted yield (yield being the mass of the product you end up with). You never get 100% yield but the higher percentage you get, the more product you will have and the less you have wasted.

19 of 20

Volcanic Eruptions

Volcanoes- formed by molten rock from the mantle when it emerges through the Earth's crust. 

Oceanic and Continental crust colliding causes volcanoes- the crust at the ocean floor is denser than than the crust below the continents. When the plates collide, an oceanic plate is forced under a continental crust. Oceanic is also cooler at the edges, so edges sink easily, pulling the oceanic plate down. As the oceanic crust is forced down it melts and starts to rise, if molten rock finds it's way to the surface, volcanoes form.

Igneous rock

Igneous rock is made when any sort of molten rock cools and solidifies. The type of rock depends on how quickly it cools and composition of the magma. Some volcanoes produce iron-rich basalt, lava from the eruption is runny and the eruption is fairly safe. If the magma is silica-rich rhyolite, the eruption is explosive. It produces thick lava.

To predict, geologists track magma movement, which can mean that they can predict with greater accuracy. Volcaanoes are unpredictable though and predictions are only estimates.

20 of 20

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Chemical resources resources »