Science unit 2 exam

Unit 2 - Chemistry

Tectonic plates more very slowley Volcanoes and earthquakes often occur where the plates meet.Its the movement of the plates against each other that cause them. Scientists use sesmic waves to study the earths structure.These are produced by earthquakes. There are two types of sesmic waves that can travel through the earth - p-waves and s-waves. P - waves: Travel through solidsand liquids,Logitudinal so travel backwards and forwards and faster then s-waves S - waves: Travel only through solids,transverse so travel in all directions and slower The theory of the continental drift is backed up by plate techtonics.Over time convection currents has moved the plate tectonics slowly apart. Alfred wegner came up with the idea of the continental drift.His theory wasnt exepted at first because there was very little evidence.But in the 1960s,scientists investigated the Mid-Atlantic ridge.They foundevidence that magma rises up through the sea floor and forms underwater volcanoes.The evidence suggested that the sea floor was spreading. When oceanic and continental plates collides the ocianic plate is pushed under the continental one.This is because it is more dense.this is called subduction.As the oceanic plate is forced down it melts and starts to rise.as the molten rock rises volcanoes are formed. Sedimentary rocks are formed from sediment in the sea or lakes.Over million of years many layers bulid up and the weight squeezes the water out the layers and produces sedimentery rock. Limestone is a sedimentary rock which is mostly formed from sea shells. When limestone is heated it thermally decomposes to make calcium oxide and carbon dioxide. Calcium Carbonate = calcium oxide + carbon dioxide CaCO3                          =       CaCO                +         CO2 Metamorphic rocks are formed by heat and pressure on sedimentary rock over long periods of time. Marble is a metamorhic rock formed from limestone.Marble is another form of calcium carbonate. Igneous rocks are formed when magma cools.They contain various diffrent minerals in randomly arranged interlocking crystals,this makes them very hard. Granite is a very hard igneous rock. Aluminium and iron are extracted from ores in rocks.Ores are minerals we can get useful materiald from. Glass is made from mealting limestone,sand and soda Bricks are made from clay. Limestone and clay are heated to make cement Cement is mixed with sand,aggregate and water to make concrete. Reinforced cocrete is a composite material.Its a combonation of concrete and a steel support.Its good for construction work as it provisdes the hardness of concrete with the flexibility and strength of steel.# Quarring can use up land and destroy habbitats Transporting rocks causes noise and pollution. Disused sites can be dangerouse.(people drowning in quarrys turned into lakes) Electrolysis is used to split pure copper from the nasty impurites.The copper is immersed ina liquid called electrolyte wicj conducts electricity.

The anode is the positive electrode.Its just a big lump of imputre copper that will dissolve.

The cathode is the negative electrode.It starts as a thin piece of pure copper and more pure copper adds to it.

The reaction at the cathode is:Cu2 + 2e- = CuReduction is the gain of electrons,or the removal of oxygen,so this is an example of a reduction reaction.

The reaction at the anode is:Cu = Cu2 + 2e-Oxidation is the loss of electrons,or the addition of oxygen,so this is an example of an oxidation reaction

During electrolysis,copper dissolves away from the anode and is deposited at the cathode.So the anode losses mass and the cathode gaines mass. Its cheaper to recycle copper than it is to mine and extract copper fro its ore. An alloy is a mixture of a metal and other elemants.They can be a mixture of two or more diffrent metals.They can also be a mixture of a metal and a non-maetal. Steel is an alloy of iron and carbon.Steel is harder than iron. Brass,Bronze,Solder and amalgam are also alloys. Smart alloys are alloys that remember there original shape and go back to them even after being bent and twisted. The word equation for oxidisation is: Iron + Oxygen + water = hydrated iron oxide. Aluminium dosent corrode when wet,however it is more  reactive then iron.Aluminium reacts with oxygen in the air to form aluminium oxide.This protects the layer below preventng any furthe reaction taking place.Alumimum has a lower density so the car body will be lighter.also it will corrode less then iron so has a longer lifetime.But the disadvantage is that it is a lot dearer then iron.Ammonia can be nutralised with acids to produce fertilisers.fertilisers are useful but if washed into lakes or rivers they can cause eutrophication.eutrophication-When fertilisers are put on fields some of it can run off into rivers and streams.The level of nitrates in the river water increases.Algae living in the water use the nutrients to multiply rapidly,creating an algae bloom.This blocks sunlight to the river plants below.The plants cannot photosynthesise,so they have no food and they die.Aerobic bacteria feed on the dead plants and start to multiply.As the bacteria multiply they use up all the oxygen in the water.As a result al the plants and animals in the river die. The harbour process takes nitrogen and hydrogen gas and uses them to make ammonia. The haber process is a reversible reaction. High pressure increases the percentage yield of ammonia.(200 atm) high tempreture decreases the percentage yield.(450 'c) Production costs depends on several diffrent factors Price of energy -- Industry needs to keep its energy bills as low as possible.If a reaction needs high tempreture,the running costs will be higher Cost of raw materials - This is kept to a minimum by recycling any materials that havent reactedLabour Costs (Wages) - Everyone who works for the company has got to be paid.Labour intensive processes ,can be very expensive.Plant costs (Equipment) - The cost of equipment depends on the conditions it has to cope with.Rate of production - The faster a reaction goes,the bettter it is in terms of reducing the time and costs of production

Salt is mined underneath chesire.rock salt is a mixture of salt and impurities.It can also be mined by pumping hot water underground.The salt dissolves and the salt solution is forced to the surface by the pressure of the water.This is called solution mining.

Unit 2 - Biology

Classification is organising living organisms into groups. Natural classification is based on the evolutionary relationships and genetic similarities between organisms. Artificial classification is based on appearance rather than genes.There used to identify organisms. Living things are  divided into kingdoms. The kingdoms are then divided into smaller groups. It goes Kingdom,Phylum,Class,Order,Family,Genus,Species. You can remember this by remembering King Philip Came Over For Great Sausages. Newly discovered species might not really fit into any of the categories. DNA sequencing allows us to see genetic differences between different groups. Evolutionary relationships can be shown with evolutionary trees. A species is an organism that can breed to produce fertile offspring. Asexual Reproduction is where an organism reproduces by making a copy of itself.There is no interbreeding with another organism so they don't fit the definition of a species. If you interbreed a male from one species with a female from a different species you'll get a hybrid.Hybrids are infertile. Organisms change and evolve over time,so the way they've been classified might also have to change.Sometimes a group of organisms will change so much it will form a new species. In the binomial system,each species is given a two-part Latin name.The first part refers to the genus that the organism belongs to and the second part refers to the species. Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain. Biomass pyramids are almost always pyramid shaped because biomass is lost at each stage in the food chain. Pyramids of numbers are similar to pyramids of biomass,but each bar on a pyramid of numbers shows the number of organisms at that stage of a food chain. Pyramid of numbers can be other shapes apart from a pyramid shape. Energy from the sun is the source of energy for all life on earth. Plants use a small percentage of the light energy from the sun to make food during photosynthesis. The energy lost at each stage is used for staying alive. Most of the energy is eventually lost to the surroundings as heat. Material and energy are also lost from the food chain as waste products. Waste products and uneaten parts can become starting points for other food chains. There can be no more than five tropic levels because by the last one there is not enough energy to sustain another population. There are two types of competition between organisms.organisms. Inter specific competition and intra specific competition. Interspecific competition is where organisms compete for resources against individuals of another species. Intraspecific competition is where organisms copete for resources against individuals of the same species. The population of a species is usually limited by the amount of food available.If the population of the prey increases,then so will the population of the predators. However as the population of predators increases,the number of prey will decrease. Parasites live off the host.They take what they need to survive,without giving anything back.This often harms the host. Mutualism is a relationship where both organisms benefit. Adaptations are the features that organisms have that make them better suited to their enviroment. Organisms that are adapted to the enviroment are better able to compete for resources.This means that they're more likely to survive,reproduce and pass on their adaptatios to their offspring. Specialists are organisms whih are highly adapted to survive in a specific habitat. Generalists are organisms that are adapted to survive in a range of diffrent habitats. Some features that help animals survive in cold conditions are: Having a thick coat or layer of blubber to insulate the body and trap heat in. Having a large size and compact body shape to give a small surface ares to volume ratio. This reduces heat loss as less body heat can be lost through the surface of the skin. Having counter-current heat exchange systems: Animals like penguins have to stand on cold ice all day. Blood vessels going to and from the feet carry blood that flows in opposite directions. The vessels pass close to each other,allowing heat to transfer between them. Warm blood flowing in arterie to the feet heats cold blood returning to the heart in the veins. This means that the feet stay cold,but it stops cold blood from cooling down the rest of the body. Some organisms have adapted to live in hot enviroments. Animals that live in very hot climates often spend the day in the shade or underground to minimise the amount of heat their bodies gain from their surroundings. Animals can also reduce their heat gain by being active at night,when it is much cooler. Animals can increase heat loss by bathing in water.As the water eveaporates it transfers heat from the skin to the surroundings,cooling the animal down. Animals that are adapted to survive in hot enviroments are often small.This gives them a large surface area to volume ratio which allows them to lose more body heat to their surroundings. Other adaptations,like having large ears,can also increase an animals surface area to volume ratio and help them to lose heat.Large thin ears allow more blood to flow near the surface of the skin. Some animals,like camels,store fat in just one part of the body.This stops the rest of the body from being too well insulated and allows heat to be lost more easily. Some desert plants: Have a rounded shape,giving them a small surface area to volume ratio to minimise water loss from the surface. Have a thick waxy layer ans spines instead of leaves to further reduce water loss. Store water in the stems to allow them to survive in times of extreme drought. Have shallow,but very extensive roots to ensure water is absorbed quickly over a large area.

Some desert animals: Have specialised kidneys that allow them to produce very concentrated urine,with a very low water content. Have no sweat glands,preventing them from losing water through sweating. Spend lots of time in underground burrows,where the air contains more moisture than on the surface.

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