C2- Chemical Resources Flashcards
What is the outer layer of the Earth called?
Lithosphere
What is the lithosphere composed of?
Crust and upper mantle
Relatively cold and rigid layer
What is the lithosphere made up of?
Tectonic plates, which are less dense than the mantle below
Where is most information about the Earth from?
Seismic waves produced by earthquakes and man-made explosions (as the crust is too thick to drill through)
What state is the mantle in?
Cold and rigid just below the crust, but at greater depths it is hot and non-rigid and able to move
What temperature is the mantle?
Increases at depths due to the Earth’s core transferring energy
What moves the plates?
Convection currents
What is subduction?
- oceanic crust is denser than continental crust
- when plates collide, oceanic plate (cooler at the margins) sinks
- pulls plate down and oceanic plate melts as it reaches the hotter part of the mantle
Why do scientists now accept the theory of plate tectonics?
- it explains a wide range of evidence
- has been discussed and tested by many scientists
What was Wegener’s continental drift theory and why has it now been accepted?
His idea was that the Earth’s continents were once joined together, but gradually moved apart over millions of years. In 1960s, new sea floor spreading evidence was found and is now accepted.
What evidence was there for the continental drift theory?
- same types of fossilised animals and plants are found in South America and Africa
- shape of the east coast of South America fits the west coast of Africa, like pieces in a jigsaw puzzle
- matching rock formations and mountain chains are found in South America and Africa
Why does magma rise through the Earth’s crust?
It is less dense than the crust and can cause volcanoes
Why do geologists study volcanoes?
- to try to forecast future eruptions
- reveal more about the structure of the Earth
Which raw materials make which building materials?
- clay ⇒ brick
- limestone and clay ⇒ cement
- sand ⇒ glass
- iron ore ⇒ iron
- aluminium ore ⇒ aluminium
What type of rock is limestone?
Sedimentary rock
What is sedimentary rock?
Rock which has formed when fragments of older rock or living things have stuck together or by precipitation
Is limestone hard?
It is quite soft as it was made from soft sediments compressed and cemented together
What type of rock is marble?
Metamorphic rock
What is metamorphic rock?
Rock which has been changed after it has formed
Is marble hard?
Marble is harder than limestone as it has been changed by heat and pressure, composed of interlocking mosaic of carbonate crystals
What type of rock is granite?
Igneous rock
What is igneous rock?
Rock which has formed when liquid rock has solidified
Is granite hard?
It is very hard as it was formed when magma cools and solidifies, made with interlocking crystals.
What is thermal decomposition?
A reaction when one substance breaks down on heating to give at least two new substances
What is the equation for the thermal decomposition of limestone?
calcium carbonate → calcium oxide + carbon dioxide
CaCO3 → CaO + CO2
How is cement made?
When limestone is heated with clay
How is concrete made?
Mixing cement, sand and small stones with water
What is reinforced concrete?
A composite material which has steel rods or meshes running through it. Composites contain at least two materials that can still be distinguished
When is concrete strong and weak?
Strong under compression (squashing) but weak under tension (pulling)
What happens when heavy loads are applied to a concrete beam?
The concrete bends, creating tension and compression. The tension crack the concrete
Why is reinforced concrete better than concrete?
It is harder and more flexible
How can impure copper be purified?
Electrolysis
What are the advantages of recycling copper?
- low melting point so energy cost to melt it is low
- reduces the need for mining, saving reserves and environmental problems caused by mining
- keeps costs of copper down
What are the disadvantages and problems of recycling copper?
- small amounts used in electrical equipment are difficult to separate
- valuable ‘pure’ copper scrap must not be mixed with less pure scrap, such as solder
- less copper is mined so fewer mining jobs
- separating process may produce pollution
- lots of copper thrown away as it is difficult to persuade people to recycle it
What electrolyte is used in the purification of copper by electrolysis?
copper (II) sulfate solution
What happens during the electrolysis of copper?
- positive anode loses mass as the copper dissolves
- negative cathode gains mass as pure copper is plated onto it
Which is the anode and which is the cathode?
- Impure coper is the anode
- sheet of pure copper is used for the cathode
What happens to the concentration of copper(II) sulfate electrolyte?
Stays the same as the impure copper dissolves, pure copper is plated on to the cathode at the same rate