C2 - chemical resources Flashcards
What is the lithosphere?
The outer layer of the earths crust.
What does the lithosphere comprise of?
The lithosphere is relatively cold and rigid and compromises the crust and top part of the mantle.
How is information about earth collected and why in this way?
The crust is too thick to drill through, so most of our information about the earth is collected from seismic waves produced by earthquakes and man-made explosions.
What is the mantle and its properties?
The mantle is the zone between the core and the crust. It is cold and rigid just below the crust, but at greater depths it is hot and non-rigid and able to move.
Why does the temperature of the mantle increase with depth?
Because the earth’s core transfers energy.
What moves the earths plates slowly?
Convection currents.
What is subduction?
Oceanic crust is denser than continental crust. When these plates collide, the oceanic plate (which is called at the margins) sinks, pulling more of the plate down, and partly melting as it reaches the hotter part of the mantle.
What is plate tectonic theory?
Plate tectonic theory suggests that Africa and South America could once have been one land mass.
What is the evidence for plate tectonic theory?
It explains a wide range of evidence.
It has been discussed and tested by many scientists.
In the 1960s, new sea floor spreading evidence was found. Subsequent research led to Wegener’s theory slowly becoming accepted.
What does magma rise up through the earth’s crust?
Because it is less dense than the crust.
What are the properties of iron-rich basalt rock?
Iron-rich basalt rock comes from runny lava in slower volcanic eruptions.
What are the properties of silica-rich rhyolite rock?
Silica-rich rhyolite rock comes from thick lava in explosive eruptions.
How can hardness of materials be compared?
By rubbing them together.
Why is limestone soft?
Limestone is a sedimentary rock. It is made from soft sediments compressed and cemented together. This makes limestone quite soft.
Why is marble harder than limestone?
Marble is a metamorphic rock formed when limestone is changed by heat and pressure, and is typically composed of an interlocking mosaic of carbonate crystals. Marble is harder than limestone because it has been baked.
Why is granite very hard?
Granite is formed when magma cools and solidifies. It is an igneous rock with interlocking crystals. This makes it very hard.
What is thermal decomposition?
Thermal decomposition is a reaction where one substance breaks down on heating to give at least two new substances.
What is the thermal decomposition of limestone (calcium carbonate)?
Calcium carbonate –> calcium oxide + carbon dioxide
CaCOthree –> CaO + COtwo
How is cement made?
Cement is made when limestone is heated with clay.
How is concrete made?
Concrete is made by mixing cement, sand and small stones with water.
What is a composite material?
Composites contain at least two materials which can be distinguished. e.g reinforced concrete
Why is reinforced concrete a better construction material then concrete?
- concrete is strong under compression but weak under tension
- if heavy loads are applied to a beam, the concrete will bend. This creates tension and compression. The tension cracks the concrete
- reinforced concrete is harder and more flexible than concrete, so is a better construction material