Science revisionThe universe and the earthStars, galaxiesGalaxiesA galaxy is a massive gravitational bound system containing stars. These may be spiral or elliptical in shape and contain 200 billion stars. The Milky Way galaxy is 2.25 million light years from the nearby Andromeda galaxy. About 24 galaxies form the Local Cluster, all moving around space together. QuasarsQuasars are distant powerful sources of light and radio waves putting out the energy of 100 galaxies. They have been identified as distant galaxies with an enormous central mass.StarsStars are huge spheres of hydrogen (H) and helium (He). Nuclear fusion occurs at 15 million degrees as hydrogen (H) nuclei slam together to form the helium (He) nuclei. (It is too hot for electrons to orbit the nucleus and form atoms). Constellations are groups of stars which form a pattern.The sun has a mass of kg and is 1.4 million km in diameter, and called a yellow dwarf. Blue giants can be 10 solar masses, while red dwarfs are only 0.1 solar masses. In size a red dwarf is less than half the suns size, while the biggest stars are supergiants of 300 solar masses and would extend out to Jupiters orbit, if placed at the centre of the solar system. Surface temperature determines a stars colour. ClassSurface Temperature (K)Colour

O30,000Blue

B10,000 to 30,000Blue/White

A10,000White

F6,000 to 10,000White/Yellow

G6,000Yellow

K4,500Orange

M3,000Red

Blue giantsThese stars are fusing very fast, so despite being 10 solar masses (Ms), they only last 3-10 million years, and then explode as supernovae. The core becomes a black hole if it exceeds 3 Ms, while cores between 1.4 Ms and 3 Ms become neutron stars, and because they spin rapidly they appear to flash or pulsate and so termed pulsars. The gravity is so intense that atoms are crushed together and therefore the star is very dense. Protons and electrons combine to form neutrons.White dwarfsThese stars have a high surface temperature (10,000 to 30,000K), so they should be bright, but since they are only Earth sized, their surface area is small, so as a result, they look dim. These stars are the cooling cores left over after red giants fail, and so therefore no fusion occurs. These stars are also extremely dense.Red giantsRed giants form when sun sized stars (0.5 to 4 Ms) burn-up all of the hydrogen at centre. As a result, the star begins to lose its outer layers; then temperature and pressure increases, until helium fusion occurs. Then the star expands, the surface cools and reddens. Luminosity, however, increases despite being cooler, due to large size.

SupergiantsSupergiants are among the most massive stars. Stars larger than the sun (classes B, A and F) will eventually expand to be 500 times larger. Supergiants typically have a mass in excess of 10-60 Ms and are up to 25,000 times more luminous than the Sun. For a given luminosity, red supergiants are larger than blue supergiants, because they radiate less energy per unit of area. Antares (the heart of the Scorpion) and Betelgeuse (Orions right armpit) are red supergiants, while Rigel (the brightest in Orion) is a blue supergiant.Red dwarfsRed dwarfs are small and relatively cool stars (they have a mass of between 0.075-0.5Ms, and a surface temperature of around 4000K), and because of this they fuse slowly, so last up to 3 trillion years. They also have a constant luminosity; and helium which builds up in the centre of the star is constantly mixed throughout the rest of the star. Then they just slowly fade away, once all their hydrogen (H) is fused into helium (He). Red dwarfs due to their low luminosity, cannot be seen from Earth with the naked eye.Brown dwarfsBrown dwarfs (originally called black dwarfs) are between the size of Jupiter and a small star (around 0.075 Ms on average). Brown dwarfs, due to their size, are not able to sustain the fusion of hydrogen into helium.Main sequenceThe main sequence ranges from red dwarfs to blue giants, fusing slow and fast respectively, and thus surface temperatures and colours respectively too.Other parts of the universeBinary starsBinary stars are a star system containing two stars orbiting around each other, and can appear as one star from a great distance. However, astronomers can identify binary stars by the gravitational influence they have on each other, which has an effect on their luminosity. Binary stars are very common. Two examples of binary stars include Sirius, and Cygnus X-1 (of which one member is probably a black hole)Black holeBlack holes are extremely small in size, but have an extremely high mass. The gravitational attraction of a black hole is so great that even light does not have the escape velocity speed to escape it. Black holes are located in the centre of every large galaxy and are believed to be created at the same time as the galaxy they are in. Stellar black holes are the remains of a giant exploded star, which had a mass of more than 3 solar masses. PulsarA pulsar is a neutron star emitting flashes of energy as it spins, emitting radiation. It appears to change its luminosity. NebulaNebulae (singular nebula) are columns of hydrogen, helium and other ionized gas, where the birth of new stars occurs. Examples include the Orion Nebula and the Eagle Nebula.

Solar system objectsMeteors and cometsComets are icy balls of rock and ice. Those that are visible from Earth, originate from the Oort Cloud or Kuiper Belt (which is located beyond the orbits of Neptune and Pluto). Comets typically orbit the Sun, and are gradually pulled apart by the gravitational exertion of the Sun. Comets have several distinct parts: Nucleus: The nucleus is the relatively stable, mostly ice and gas core of the comet. Tail (coma): Solar radiation and solar wind from the Sun causes the comet to form a trail of dust and gases. This trail of dust and gas is visible due to the Suns radiation, which is reflected, or gases glowing due to ionization. The difference between a meteor and a comet is that a meteor is a shooting star an object that has entered the atmosphere, possibly a comet that has entered the atmosphere, while a comet is an icy ball of rock with 2 tails, 10 km across and orbiting the sun.AsteroidsAsteroids are rock objects that can be up to 250 km across. Mars two moons Deimos and Phobos were probably asteroids, while Jupiter has many satellites that were probably asteroids. Asteroids are located predominantly between Mars and Jupiter, with some located in the Kuiper Belt, and some located in close proximity to Earth.PlanetsPlanets are spherical objects, not large enough for fusion, but large enough to be rounded by its own objects. Origins of the universeThe steady state theoryThe steady state theory, which was proposed in 1948, states that there was no beginning to the universe. It had always existed. The theory states that galaxies are continually moving away from each other. In the extra space, new stars and galaxies are created. Those new stars and galaxies replace those who move away, so that the universe appears the same.Origins of the big bang theoryThe Big Bang theory was a name used by one of the developers of the steady state theory, Fred Hoyle, to ridicule the makers of the theory. The big bang theory was first proposed in 1927 by Georges Lemaitre, a Catholic Priest from Belgium.Evidence for the big bangMost galaxies show the red-shift of their light because they are moving away. This is a good evidence for an expanding universe since its beginning 13.7 billion years ago in a Big Bang.Theoretical physicists predicted certain conditions if there was a Big Bang rather than the Steady State theory being true. (In thus, the later theory, the universe always existed and matter spontaneously popped into existence. The Big Bang however implies a beginning).Conditions:1. Hydrogen + Helium in 80:20 ratio2. CMB = cosmic microwave background radiation should exist as a remnant of the Big Bang.3. Expansion proved by the observation of red shift of light from galaxies.4. It should look less evolved if we observe it (using Hubble or Keck) further back in time. e.g. In January 2011, Hubble has viewed galaxies formed only 300,000 years after Big Bang.There are still problems. The idea of inflation needed to be added on in 1980 to explain why the universe is already so big.red shift of galaxiesThe movement of the stars towards or away with relation to the Earth can be measured using the Doppler Effect. Doppler noted the effect on sound waves and relationship between pitch and distance. This is notably present in our daily lives, with high-speed trains and aeroplanes.When observing light from a distant star, some dark lines are observed. These dark lines correspond to the colours of light, which have been absorbed by the substances within the star. Different substances absorb different wavelengths, and therefore different colours. By identifying, the missing wavelengths (colours), astronomers can figure what elements compose the star. In many cases, these missing wavelengths (colours) are shifted from their expected positions. These changes, referred to as Doppler shifts are: Red shift when the missing wavelengths shift to longer wavelengths, which have lower frequencies or more redder frequencies than expected is called a red shift and results from a star moving away within relation to the Earth. Nearby objects such as Sirius (the Dog Star), are moving away from us and display this red shift. Blue shift when the missing wavelengths shift to shorter wavelengths, which have higher frequencies or more bluer frequencies than expected is called a blue shift and results from a star moving closer within relation to the Earth. Some stars show alternate changes between red shifts and blue shifts suggesting that the star is under the gravitational influence of an orbiting star. The brightness of the circling star reduces corresponds to the appropriate shift of the main star moving in response to the gravitational influences of the other star.On a much larger scale, the study of Doppler shifts can determine the movement of galaxies, and provides an amazing picture of the universe. A relatively small amount of galaxies, including the Andromeda Galaxy is moving towards us, but the majority of galaxies display red shift, and are moving away from the Earth with considerable speed.Astronomer, Edwin Hubble (of which the Hubble Space Telescope is named in honour of) first investigated the relationship between the size of the red shift and the distance with relation to Earth. This is called Hubbles Law. This law states the further away a galaxy if, the greater its red shift is, and therefore the faster it is moving away from us. This red shift is present from any point within the universe, not just the planet Earth, as this is consistent with Hubbles law.The afterglowAs space expanded, the temperature cooled. Positions (positively charged electrons) and electrons formed, and then these collided to form protons and neutrons, which eventually formed the nuclei of the first 3 elements. When the temperature cooled enough, the nuclei captured the electrons, forming the atom.George Gamow and Ralph Alpher proposed their version of the big bang theory in 1948. They calculated that the universe would have a temperature of 2.7 C or (2.7 K) above absolute zero. That is -270C or 2.7 K. Anything with a temperature above absolute zero (0K or around -273.7C) emits radiation. The nature of the radiation depends on the temperature.Gamow predicted that because its temperature, the universe would be emitting an afterglow of radiation. This afterglow became known as cosmic microwave background radiation and was discovered in 1965. Its discovery put an end to the steady state theory.The end of it allThere are three theories for how the universe might end: The big crunch theory: The big crunch is where the universe will snap back onto itself in a big crunch. If this happens, the end result will be a single point, the singularity. Some cosmologists believe that this will be followed by another big bang. The big freeze theory: The big freeze is where the expansion of the universe continues and stars use up all their fuel and burn out, causing planets to freeze. The universe would then consist of scattered particles that would never meet again. The big rip theory: The big rip is where the universe rips itself apart violently as a result of expanding at an increasing speed. According to this theory, the end of the universe will also be the end of time itself.

Origins of the solar system The universe is thought to be 15-20 billion years old. Some stars in our galaxy are thought to be 13 billion years old. Our Sun is about 4.6 billion years old. In about 5 billion years from now, our sun will become a red giant then white dwarf and die. This implies our Sun is a young star. The most accepted theory for the formation of the solar system is the Nebula Hypothesis. According to this theory an interstellar cloud of hydrogen gas or nebula is ejected from an exploding older star. At some point inside the nebula, shockwaves could have caused the gases to spin (in what is referred to as an angular motion) and collects more matter (in the form of hydrogen gas) due to the force of its own gravity, eventually forming our Sun. (The Sun takes up about 98.2% of the total mass of the Solar System) The gravity potential energy caused by the growing star (in this case, our Sun) is converted to heat energy. When the surface temperature reaches 11 million C, nuclear fusion begins. Elements formed up to iron (element no 26) within a star, other elements require too much more energy and are formed during supernovae (sing. supernova). Elements are not formed within a planet such as Earth, as the temperature is not hot enough to cause nuclear fusion, yet new compounds are formed within the centre of the planet. As the rest of material whirled around the disc of the Sun it formed clumps. These clumps eventually are thought to have formed the planets and moons.The electromagnetic spectrumElectromagnetic (or EM) waves all travel at the same speed in a vacuum. This speed is m/s or around m/s or 300,000 km/s. In glass the speed drops to m/s. The waves all have different frequencies (f) and wave length ()

WavesThe following symbols are used to represent properties of waves: T period of time in seconds (time for wavelength to pass a given point) A amplitude in metres, that is distance from 0 to crest or trough (height of crest) f frequency in hertz (Hz) (no of waves per second) (lambda) wavelength in metres v velocity speed in metres per second 2a the wave height, is equal to twice the amplitude and is in metres Transverse waves are waves where the particles oscillate back and forth perpendicular to the direction that the wave is moving. Longitudinal waves are waves where the particles oscillate back and forth along the direction that the wave is moving.Properties of lightLight is made by luminous bodies such as stars, incandescent light-bulbs, fluorescent tubes, glow worms and fireflies (bioluminescence) and glow-sticks (chemiluminescence). A lighthouse vibrates in all directions; its light is said to be unpolarised. A polarised filter will enable only the direction to pass, thus polarising the light.Wavelengths of visible lightLonger wavelengths Infra-red (IR) is 700 nanometres to about 2-3 mm Microwaves are slightly longer at around 10 centimetres in ovens, but 1 or 2 centimetres if going up to satellites Radio waves can be 1-2 metres long and even up 5 kilometres in length.Shorter wavelengths UV rays are from 400 to 100 nanometres X rays are even smaller from 100 nanometres down to 0.1 nanometres rays (gamma rays) are 0.1 nanometresRocks, fossils and earthquakesTypes of rocksa. Sedimentary rocks Due to the weathering process, extrusive igneous rock, metamorphic or sedimentary rocks, remains of dead animals and plants, form sediments (accumulation of weathered rocks) lead to sedimentary rocks. This process is called lithification. The lithification process involves many steps.i/ Sediments build up at the bottom of river beds, lakes and seas. The pressure of the top layers and water squeezes the sediments.ii/ Water moving through the compressed sediments carries minerals which help cement the particles together.NameResulted From

SandstoneSand

MudstoneMud

ConglomerateDifferent size particles

LimestoneRemains of the organisms

ChalkRemains of tiny sea organisms and their skeletons

Coalcompressed plant material

b. Igneous rocks formed from the solidification of molten materials from within the Earth such as magma and lava from the mantle (lava is the magma that spews out of a volcano). i/ Lava cools quicker than magma, because it is above the Earths surface and thus the crystals formed are smaller in size or non-existent. These rocks are called volcanic or extrusive. Examples include pumice and basalt.ii/ Magma that cools slowly (below the surface of the Earth) forms intrusive igneous rocks or plutonic rocks which contain large crystals (the slower the rate of cooling, the larger the crystals). Examples include granite.c. Metamorphic rocks are sedimentary or igneous rocks which are changed (metamorphosed) due to pressure or temperature or both. Metamorphic rocks are stronger than the mother rock (protolith) because their particles are fused together. Metamorphic rocks can further be changed due to pressure and temperature.NameCourse of changeResulted From

Limestone (sed.)HeatMarble

Granite (ign.)Heat + PressureGneiss

Shale (sed.)PressureSlate, phylite, gneiss and then schist.

SchistHeatGneiss

Quartz (sandstone)Heat + PressureQuartzite

The law of superposition According to the law of superposition, suggested by the English surveyor William Smith (1760-1839), during the process of rock formation younger rocks superimpose on top of older rocks. However, when the layers of the rocks are folded or faulted, it becomes less obvious the order of the stratigraphy. In this case, geologists look at the fossils in order to determine the age of the rock layers. The most advanced and complex fossils of organisms are the youngest. Sometimes igneous intrusions or extrusions can change the sequence of sedimentary rocks. Sills and dykes spread between sedimentary layers and cut across. This process is known as the law of cross-cutting relationship. This law states that igneous rocks that intrude other rocks are younger than the rocks they intrude. The size of crystals of igneous rocks increases with depth of cooling, due to the slower cooling rate. Other processes that change rocks overtime include:a. Metamorphism a process by which sedimentary rocks change over time due to heat or pressure (or both)b. Unconformities are due to the discontinuity in the geological history of an area. For example, erosion can cause deposited layers of rock to disappear overtime so there is a gap in the geological history in that area. New layers can be deposited over the older ones.Dating of fossils and rocks layers Absolute fossil age refers to the actual age of the fossil. However, the absolute age of fossil can never be 100% accurate. Relative fossil age indicates whether one fossil is older or younger than another one.

About radiometric dating This method is used for determining, the absolute age of a rock or fossil. This is based on the radioactive decay of radioisotopes. Carbon dating is one widely used radiometric dating type to determine the age of fossils up 50,000 years.Radioactive ElementDecay productHalf-life

Rubidium-87Strontium-8747 billion years

Uranium-238Lead-2064.51 billion years

Potassium-40Argon-401.3 billion years

Uranium-235Lead-2070.71 billion years

Carbon-14Nitrogen-145730 years

Living things are made up of mainly Carbon-12 and small amounts of Carbon-14. Carbon-14 is unstable and decays into nitrogen. Carbon-12 is stable. After an organism dies, the Carbon-14 decays but not the Carbon-12. By measuring the ratio of Carbon-14: Carbon-12, we can determine the time of death (so the age) of the organism. Rock types containing fossilsSedimentary rocks such as sandstone, limestone, shale (mudstone), siltstone, coal and conglomerate may contain fossils. The finer the grainsize, the better the detail of preservation will be. Metamorphism will heat and squeeze rocks and destroy any fossils, e.g. no fossils in slate, schist or gneiss. Marble is metamorphosed limestone (full of coral, shells) and will still show the fossils if it only is partially metamorphosed. Igneous rocks such as pumice, granite, basalt and dolerite were once underground molten magma, and so therefore do not have any fossils.Types of fossils1. Unchanged soft parts rare in existence e.g. woolly mammoths from Siberia and Alaska, are only 10,000 to 20,000 years old.2. Unchanged hard parts e.g. (1) insects trapped in amber (hardwood tree sap)e.g. (2) shells and bones3. Changed hard parts The bone or shell is replaced by mineral such as calcite (carbonisation), that is calcium carbonate, maintaining the exact shape. This is a cast. Trees turn into petrified wood, which is made of silicate materials. In some cases, the tree or bone becomes opalised and has rainbow colours 4. Impressions bones, shells, and leaves can leave an imprint in fine sediments. This is the reverse image, and is called a mould. 5. Microfossils they are hard to detect, due to their extremely small size and include pollen, algae and bacteria.6. Trace fossils foot prints are included here of which massive dinosaur footprints can be up to 1 metre across. Also root tubes and coprolites (poo).The process of fossilisation Fossilisation is a rare event, due to organism being easily decomposed by micro-organisms. It is the process of burial and preservation of the specimen. If oxygen is excluded, the micro-organisms (bacteria) cannot decompose the flesh. Rapid burial, by dirt, mud, silt, or lava etc., favours best preservation. In March 2011, a 700 year Chinese women was excavated from a depth of 2 metres. She was in an excellent condition with skin, eyelashes and a green ring-stone present.Otzi, the iceman, was found in 1991 in the Austrian Alps. He is kept frozen and has sterile water sprayed on his skin which freezes into clear ice and keeps oxygen away.Index fossilsSome fossils lived over comparatively short period and were widely spread. These are known as index fossils and help us determine the age of layers of rocks of which they are found.For instances, different species of ammonites found in different parts of the world are used to determine the age of layers of rocks within a million of years or so. A more primitive ammonite indicates that the layer is older than other layers where more developed species are found.

Dating fossils accuratelyRelative dating is used to determine the relative age of a fossil. As the layers of sedimentary rock are usually arranged in the order they were deposited, so are fossils, which means the more primitive species fossils are found further down than the more developed species fossils.In order for relative dating to be accurate, consideration of the earths movement needs to be considered. Such movements include folding, and faulting. If the process is enough, to metamorphise the rock, the fossils would be destroyed. Layers containing fossils may have been thrust upwards or sideways, and this needs to be taken into consideration, when investigating the relative age of fossils within rock layers.For the absolute age of a fossil, absolute dating is used. The accuracy depends on the measuring instrument used, and also if the age of the fossil is old enough, than it becomes harder to become more absolute. Radioactive (isotope) dating can be used to determine this.Faults and earthquakesA fault is defined as a fracture in rocks due to stress and strain which breaks the rock. Some well-known faults: San Andreas Fault California, USA Alpine Fault New Zealand North Anatolian Fault TurkeyA fault line is a fracture where the crust has moved. Following the 1855 Wellington Earthquake in New Zealand, geologists were able to establish the connection between fault lines and earthquakes. As far as seismologists can understand is that all, but the deepest earthquakes (600 km or more deep) occur on faults. Seismic waves are generated when the two sides of the fault rapidly slip past each other: P waves (primary waves) have a speed of 10 kilometres per second only. These waves are only detected by seismometers, which are instruments measuring earthquake waves. S waves (secondary waves) have a speed of 6 kilometres per second. They are felt as preliminary tremors. L waves (surface or longitudinal waves) causes all the destruction, but are less than 150 kilometres (in length)For most earthquakes, the faults do not break the surface, so the faults can be seen only through analysing the seismic waves. Faults can be anywhere from a few metres to several thousand kilometres long. Seismologists still have to learn more about the mechanism that causes the deepest earthquakes. At 600+ km deep, the earth is probably too warm for faults to be brittle like glass, so some form of chemical change might occur very rapidly.Every plate comes in contact with another plate at its boundary: Spreading zones are where the plates move apart e.g. at mid-ocean ridges. Subduction zones are where one plate rises over the top of another. They occur at the edge of some continents e.g. Japan and western South America. Volcanoes form at subduction zones, and earthquakes are common due to friction between plates. Collision zones are where two plates collide. These two layers fold to form mountainse.g. the Himalayas and areas of Southern Europe. Transform fault zones are where plates slide past each other, in opposite directions causing earthquakes, e.g. the San Andreas Fault, California, US and the Alpine Fault, South Island, New Zealand.An earthquake is a naturally occurring movement of the earths crust, beginning suddenly and of short duration, which causes vibrations to travel through the earth.FoldingGeological folding involves the bending or buckling of a single or multiple layered strata such as sediments and rocks, which were originally a plane surface. The cause of this is a gradual build-up of strain.Types of folds: Anticline folds these folds concave upwards, with the oldest rocks in the middle. Syncline folds these folds concave downwards, with the youngest rocks in the middle. Monocline folds these folds have a structure similar to steps. An example of a monocline fold is between Penrith and Lapstone in the Blue Mountains.Continental driftMeteorologist Alfred Wegener proposed the idea of moving continents in 1912 (which wasnt popular with geologists). He stated that all the earths landmasses were clumped into one supercontinent termed Pangaea.Proof of continental drift came from: The jigsaw fit of the coastlines Similar rocks and fossils where the coasts fit.Sonar could show the ocean floor topography of trenches, abyssal plains, volcanic peaks and mountains. Harry Hess proposed that the sea floor spread apart to the underwater mountain ridges. Hot magma welled up in the mantle and split the crust at the ridge.Confirmation of sea floor spreading came in 1965. Underwater eruptions of basaltic lava had a trace of Earths magnetic field recorded in minerals containing iron. (The field reverse every thousand years). An almost mirror image of stripes was detected by magnometers, either side of the Mid Atlantic Ridge. (The same sort of pattern exists over all other ridges). The theory was then confirmed.In 1968, the Glomar Challenger drilled into the sea floor at many spots on an 18 month voyage. Results showed that near a mid ocean ridge sediments were thinner and had younger fossils. Further from the ridge the sediments were thicker and contained older fossils.No ocean floor was older than 200 million years. Oceanic crust (under the sediments) is basaltic, while continental crust is granitic which is less dense, and therefore floats on the basalt. GeneticsCell division in animals and plantsWhen an animal cell is to divide, the nucleus begins to split into two parts. The cytoplasm then starts to also separate, forming two daughter cells. In the cytoplasm, structures also divide, and are shared equally with each of the daughter cells. The new daughter cell absorbs the nutrients it requires to grow. Often one of the daughter cells will continue to divide further into new cells.When a plant cell is about to divide, the nucleus becomes larger and the vacuole disappears. Then the nucleus divides. New cell walls grow to separate the two daughter cells. Small vacuoles join together to form a large vacuole. These form in one of the two daughter cells. Chloroplasts are shared between each daughter cell. Water is then absorbed to make this cell larger. One of the daughter cells divides again.Structure of DNARNA and DNA are macromolecules found in the nuclei of cells. Some DNA is also found in organelles called mitochondria that generate energy for the organism. RNA is located in small structures in the cells cytoplasm called ribosomes. This is where protein synthesis occurs within the cell.DNARNA

Sugar group: DeoxyriboseSugar group: Ribose

Nitrogen bases: Adenine (A) Thymine (T) Guanine (G) Cytosine (C)Nitrogen bases: Adenine (A) Uracil (U) Guanine (G) Cytosine (C)

In early 1950s, Rosalind Franklin and Linus Pauling used X-ray crystallography to determine the structure of DNA. They observed the X-ray scattering patterns from the DNA in the hope of accurately determining the structure of the DNA molecule. In 1953, James Watson and Francis Crick, using data collected by Franklin, deduced that the DNA consisted of a double helix. (This won them the 1962 Nobel Prize)DNA consists of two helical strands similar in structure to a twisted staircase, and is composed of molecules called nucleotides. Each nucleotide is composed of three parts; a nitrogen base, a sugar, and a phosphate group (refer to table). Alternating sugar and phosphate groups make up the sides of the ladder, while the nitrogen bases join to form the rungs of the ladders. In DNA, Adenine joins with Thymine, and Guanine joins with Cytosine, while in RNA, Adenine joins with Uracil, and Guanine joins with Cytosine.DNA replicationDuring normal cell division, the DNA double-helix must unwind to form two new strands. New nucleotides are transported towards these strands and link them according to the bases that join together. When fully replicated the two new strands wind back up into the double-helix form. Each double helix strand then becomes part of the chromosomes that move to opposite ends of the cell. When two new cells are formed, each has an identical copy of the DNA structure in its nucleus. Genes represent certain sequences of nitrogen bases along the DNA strand. Sequences of three nitrogen bases form a triplet code. The code is then read (decoded) by a RNA molecule. The RNA molecule moves to the ribosomes in the cytoplasm where the code is translated into an amino acid. A triplet code of CCA produces a different amino code to that produced by the CGT code. For any one amino acid, there are a number of alternative codes. For e.g. glycine, the simplest amino acid has four codes, CCA, CCG, CCC and CCT.The theory of evolutionDarwins theory of evolutionAdam Sedgwick (1785-1873) was a geologist who had studied primitive fossils of Wales and Scotland. This led to establishing the Cambrian Period as the beginning of the Palaeozoic era. Through these studies of fossils and strata, he became convinced that the Earth was extremely old, and that a series of great catastrophes had wiped out most of the life forms, at various stages in the Earths history. He also believed in divine creation of life over long periods of time.George Cuvier (1769-1832) was studying the anatomy of living organisms and comparing with that of fossils. By studying what appeared to be similar fossils, he was able to prove extinction of many species, due to great catastrophes. Cuvier did not believe that living things could change over time.Louis Agassiz (1807-1873) was a Swiss-American geologist, who had studied the movement of glaciers. He realised that signs of glaciation could be seen where none were present today, suggesting a great Ice Age once gripped the Earth, and caused massive extinctions. He also noted that the simpler life-forms were found in lower layers than the more developed. He described it all as the grand work of God.Charles Darwin (born 1804) was chosen by Sedgwick in 1831 to assist in studying the geology of North Wales. Later, Darwin went on a five year voyage, studying numerous species and great variations between species. On the Galapagos Islands, he observed many species of finches and giant tortoises. Darwin started to think that the population on finches on each island had originated from birds that had arrived from the mainland. He reasoned that the changes on each island, had led to gradual changes in the finches, until the finches eventually became different from each other. For example: some finches had adapted to feeding on insects and lived mainly in trees. Others lived in low shrubs on the ground, and had different shaped beaks, and also a different diet.Darwin proposed the theory of natural selection: There is natural variation within a species. In nature, there is a struggle for existence. Organisms with more favourable variations (characteristics) survive in greater numbers and reproduce. The next generation will have more individuals that have inherited this favourable characteristic. Over time, the characteristic of the population change as the favourable characteristics are preserved. These became more adapted to the environment.He used this theory to explain the variation between the finches. He argued that the variations in the natural population had meant that certain characteristics were favoured on one island, and other characteristics on another. The geographic isolation had meant that populations had rarely inbred, and so each of the different species evolved separate to one other.

PhysicsVelocity, acceleration and distance Vectors and scalar quantities Scalars are physical quantities that have magnitude (i.e. size, value)Examples: distance, speed, pressure, temperature, money, work, current, time etc. Vectors are physical quantities that have magnitude and direction. Examples: displacement, velocity, acceleration, electric field, magnetic field, force etc.Distance and displacement Distance is the total length between two points, the route it covers. Displacement is the shortest length between length between one point and another in a given direction.AB

Graphs with distance or velocity against timeGraphing distance (or displacement) with time1. From this graph we can read directly:a. the position of the objectb. the time at which the object is at a particular position2. We can calculate the velocity/speed of the object from the slope of the graph. 3. We can also work out is the object is moving or not.4. We can work out if the velocity/speed is constant or not and hence if the object accelerates or not.5. Constant velocity/speed means no acceleration while a variable velocity/speed implies acceleration.Graphing velocity (or speed) with time)1. From a velocity/time graph we read directlya. The velocity/speed for a particular timeb. The time for a particular velocity2. The acceleration by measuring the gradient of the graph for a particular time interval.3. The distance and displacement of the moving object by calculating the area under the graphDistance = Total AreaDisplacement = Area below t axis Area below t axisCalculating accelerationAcceleration = v = final velocity/speed (ms-1)u = initial velocity/speed (ms-1)a = acceleration (ms-1)t = time (sec)Equations of linear motion1. 2. 3.

Newtons Laws of motionsFirst law: The Law of InertiaThis law states that an object will remain at rest or will not change its velocity (speed and direction) unless it is acted upon by an outside unbalanced force.All objects that have mass experience inertia, which is dependent on the amount of mass.Second Law: The Law of AccelerationThis law states that the acceleration of an object is proportional to the net unbalanced force acting on the object, and is inversely proportional to the mass. F Combining this two formulas to get a = or F = maThird Law: The Law of Action and ReactionThis states that all forces occur in pairs and these forces are equal in magnitude but opposite in direction. Weight and mass1. Mass refers to the amount of matter in an object. Mass does not change from one place to another.2. Weight is a special type of force due to the gravitational attraction of the Earth or any other planet(moon etc.)Weight (N) = Mass (kg) Acceleration due to gravity (ms-2)W = mgKinetic energy, potential energy and momentumKinetic energyKinetic energy is the energy of motion. Bodies with a greater velocity have greater kinetic energy. The formula for the amount of kinetic energy in an object is:where energy (KE) is in joules (J), mass (m) in kg, and velocity (v) in ms-1.Gravitational potential energyGravitational energy is the energy an object has due to gravity. Its formula is:where energy (GPE) is in joules (J), mass (m) in kg, height (h) in metres, acceleration due to gravity (g) in ms-2When a body is falling, the sum of the amount of gravitational energy and kinetic energy is constant, if no energy is lost as heat or sound.Elastic potential energyAn ideal spring will follow Hookes Law which is F = kx so therefore the elastic potential energy in a spring is:where energy (EPE) is in joules (j), x = distance stretched (in m), that is total distance when stretched distance when un-stretched (in m), k = spring constant. If the string is released, the energy is converted into kinetic energy.MomentumMomentum is proportional to both mass and velocity. The greater the velocity or mass, the greater the momentum, so therefore: where momentum (p) in N.s, mass (m) in kg, velocity (v) in ms-1WorkWork is a scalar quantity related to energy and is proportional to both force and distance. Its formula is: where work (W) in newton metres or Joules (J), Force (F) in Newtons, and distance (s) in metres.GravityGravitational attractionGravity is a force of attraction between two masses.This force increases as the product of the masses increases:

This force decreases as the square of the separation between the masses increases.

Combining proportionalities:

Turning the proportionality into an equality, where G is the gravitational constant of the universe, approximately , and s is the distance between m1 and m2WeightlessnessGravity exists everywhere in our Universe. Astronauts floating in an international space station appear to be weightless, without gravity but what is really happening is that both the astronauts and the space station are falling at the same time and at the same rate (g = 9.8ms-2). Both the astronauts and space station fall at the same rate, but the curvature of the Earth means that it never touches the surface of the Earth. Absorbtion, reflection and refractionAbsortionThe process of absorption occurs when sunlight (white light, light containing all frequencies) strikes the object, the atoms of that object get excited by vibrating its electrons because light is a form of energy. But only some frequencies of light (some colours) most easily excite those atoms. These frequencies of light are absorbed into object that is the energy contained in these frequencies of light starts up the vibrations of electrons. These vibrations are slowly converted to heat as the electrons collide with neighbouring atoms.Hence these absorbed frequencies are used to heat up the object, which is why black objects conduct heat well. The frequencies that were not absorbed are reflected off the surface and it is these frequencies that are visible to eye, and give the object its colour.ReflectionReflection is when a ray of light bounces off at the same angle in which it hits the object. The law of relationship between the angle of incidence and the angle of reflection is: Reflection is also used in optic fibres.RefractionRefraction is when a ray of light enters a material of different density and the ray of light bends, for e.g. when the ray of light enters a denser material like glass and vice versa. Also (does not include extra variables that could affect the light):

The two things to note:1. Light bends towards the normal when it enters a material of a greater density (at an angle) and slows down.2. Light bends away from the normal when it enters a material of a lesser density (at an angle) and speeds up.Light travels at 299 792 458 kilometres per second in a vacuum. When light enters any other medium, light slows down and bends. The refractive index (r) measures the change in velocity when light enters a material of different density.

where r is the refractive index, c is the speed of light, v is the speed of light in another medium. Some common substances and their refraction indexes:SubstanceRefraction Index

vacuum1

air (at sea level) slightly greater than 1

ice1.31

water (at 20C) 1.33

ethyl alcohol (at 20C) 1.36

human eye - corona 1.37-1.4

human eye - lens1.4

glass (crown glass - pure)1.52

sodium chloride1.55

Curved surfacesA mirror is an object that reflects light. A lens is an object used for refracting light or bending light. Curved mirrors include the convex and concave mirrors. Light rays converge to a point called the focus in a concave mirror. Light rays diverge from a focus in a convex mirror.The image at the focus can be seen. If real light rays pass through the focus we say that a real image is made. Real images can be shown onto a screen e.g. like a movie projector. If virtual rays pass through the focus, then we say that a virtual image is made. These images cannot be shown onto a screen.

ChemistryElements of chemistryHistory of chemistry and atomic theoryDemocritus envisaged the concept of powdered rock having no possible smaller particle. He said it was atomos meaning indivisible. This became the English atom the smallest part of an element. Alchemists tried turning lead into gold and making the elixir of life. Eventually the science of chemistry evolved as new elements and compounds were discovered.the periodic table1. The elements are listed in order of increasing atomic number (Z), by the number of protons in the nucleus. The simplest element is Hydrogen (H) with Z = 1. 2. The elements with 1 electron (e-) in its outer shell are placed in Group I. Groups are the vertical columns of the Periodic Table. The elements with 2 electrons (2e-) in their outer shell are placed in Group II and so on.3. Group VIII elements have full outer shells and are called Inert or Noble gases.4. Special names are also given to Group I, II and VII. Group I are the Alkali Metals because the hydroxides of these metals are alkalis (i.e. basic). Group II elements are called the alkaline earth metals. They also make oxides which are alkaline. Group VII elements are called halogens (from the vapour of iodine which produced a halogen)5. The Transition Metals are the elements which have more complicated arrangements. This group contains many common metals such as Iron (Fe), Nickel (Ni), Copper (Cu), Zinc (Zn), Silver (Ag), Lead (Hg) and Gold (Au).6. The Periods are the horizontal rows of the periodic table.Atomic and mass numbers Atomic number (Z) refers to the number of protons in the nucleus of the atom. Mass number (A) refers to the number of protons and neutrons in the nucleus.Therefore to calculate the number of neutrons in a nucleus we subtract Z from A.

Chemical groups and their propertiesThe elements in a Group resemble each other. Sometimes they look alike, and in general behave in the same way. This is due to the number of electrons (e) in their outer shell.Group I The alkali metals The first three elements in this group are lithium (Li), sodium (Na) and potassium (K). They are solid metals which are stored in jars of oil because they are very reactive. They are light and float on water (density of less than 1 kg.m-3) They are silvery in colour and shiny when freshly cut but quickly tarnish due to oxidation. They must always cut under the surface of paraffin oil. They are soft and melt easily due to their low melting point (m.p.) and boiling points (b.p.), compared to other metals. They are conductors of electricity.The electron configuration for Group 1 elements:Li21

Na281

K2881

Rb281881

Cs28181881

Fr2818321881

The reactivity of the elements in this Group increases downwards (i.e. francium is most reactive, and lithium is the least reactive). NOTE: The reactive series of metals is: K, Na, Ca, Mg, Al, Zn, Fe, Pb, Cu, Ag, Au, and Pt

Group II The alkaline earth metals The most reactive elements in this Group, strontium (Sr) and barium (Ba) must be stored under paraffin oil. The others can be left in air because their oxides layers protect them. They are all silvery-grey and shiny when freshly cut. They have higher melting and boiling points compared to Group I elements. They are denser than Group I elements and sink in water. They are harder than Group I elements. They have better conductivity than Group I elements.Group Vii: The halogensThese elements exist as diatomic molecules (F2, Cl2 etc.) They are all coloured non-metals. They do not conduct electricity. At room temperature: Fluorine is a very pale yellow gas. Chlorine is a yellow green gas. Bromine is a red-brown fuming liquid. Iodine is a black purple solid. They are all poisonous. They have similar chemical properties because their atoms have 7 electrons in their outer shell.NOTE: The reactivity for groups I and II, increases downwards and across to the left in the periodic table. For groups VI and VII, the opposite is true.Non-metals such as fluorine have greater reactivity as they have more shells closer to the nucleus, thus more electrostatic forces thus more reactive than chlorine.Group Viii or O: The noble gasesThese elements are all gases found in small quantities in the air. They have no smell or colour. They do not conduct electricity. No compounds of these elements are found in nature. It was in 1965 that an English chemist, Bartlett, managed to be Xenon and Krypton react for the first time. Research is still going on today. The noble gases are unreactive because their atoms have full outer shells.Chemical equationsExamples of chemical equationsThe reaction between carbon and oxygenWhen carbon is heated in oxygen, they react together, and carbon dioxide is formed. The carbon and oxygen are called reactants, because they react together. Carbon dioxide is the product of the reaction.Its chemical equation is: C(s) + O2 (g) CO2 (g)The reaction between hydrogen and oxygenWhen hydrogen and oxygen react together, the product is water. Its chemical equation is: 2H2 (g) + O2 (g) 2H2O (l)Adding more information to equationsReactants and products may be solids, liquids, gases or solutions. You can show their states by adding state symbols to the equations. The state symbols are:(s) for solid(l) for liquid (g) for gas(aq) for aqueous solution (solution in water)Further examples:1. Calcium burns in chlorine to form calcium chloride, a solid. Therefore its chemical equation is: Ca(s) + Cl2 (g) CaCl2 (s)2. In industry, hydrochloric acid is formed by burning hydrogen in chlorine. Therefore its chemical equation is: H2 (g) + Cl2 (g) 2HCl (g)3. Magnesium burns in oxygen to form magnesium oxide, a white solid. Therefore its chemical equation is: 2Mg(s) + O2 (g) 2MgO(s)

Elements, compounds and ions An element consists of only one type of atom: e.g. Fe, O2 and S6 A compound consists of two or more different atoms, chemically bonded together (note: if they are not chemically bonded they may be a mixture or alloy): e.g. H2O, H2SO4 and CO2 Ions are charged particles. Positive ions are formed when metal atoms lose electrons, e.g. Na+, Mg2+ and Al3+. Negative ions are formed when non-metal ions gain electrons e.g. Cl, S2 and N3 A polyatomic ion or radical is a charged particle made up of more than one type of atom, e.g. NH4+, SO42 and CO32Chemical bondingAtoms gain or lose electrons to form anions (negatively charged ions) and cations (positively charged ions). This is because each atom prefers a full outer shell, for example the ionic bond between Na and Cl.Bonding between pure metals: The bonding between metals, e.g. iron (Fe), gold (Au) and calcium (Ca), is called metallic bonding. All metals are solid at 25C except mercury (Hg), which is liquid.Covalent bonding Covalent bonding is the sharing of electrons and occurs only between non-metals and other non-metals, like carbon (C) and oxygen (O), sulfur (S) and hydrogen (H), nitrogen (N) and fluorine (F). A molecule is composed of non-metals and is the smallest number of atoms that exist bonded together in a stable form. Atoms of the noble gases exist by themselves and are called monatomic. For carbon dioxide, a molecule consists of one carbon atom and two oxygen atoms covalently bonded together. This molecular formula represents the number and types of atoms in the compound. A diatomic molecule consists of two non-metal atoms covalently bonded together. Elements that exist as diatomic molecules are the gases hydrogen (H2), oxygen (O2), nitrogen (N2), fluorine (F2) and chlorine (Cl2), the liquid bromine (Br2) and solid iodine (I2)Ionic bonding Ionic bonding almost always involves metals combined with non-metals. Ionic compounds are crystalline solids, unless dissolved in water as an aqueous solution. The formula of an ionic compound is not a molecular formula, since ionic compounds form large crystal lattices, not molecules. Instead the formula shows the ratio of ions in the crystal. For example, the ionic compound magnesium oxide has the formula MgO. This doesnt mean that one atom of magnesium and one atom of oxygen move around together; it means that in any sample of magnesium oxide, the ratio of magnesium ions Mg2+ to oxide ions O2 is 1:1. A small crystal may contain 1000 ions of each, while a larger crystal may contain millions of ions of each The formula still stays as MgO. Sometimes more than one of a polyatomic ion is needed in a formula. This is when brackets are used, for example Fe2(SO4)3, Ca(OH)2, (NH4)2CO3 Ionic bonds are broken with the substance is dissolved in water.The law of conservation of matterThe Law of Conservation of Matter (or Law of Conservation of Mass) states that: matter cannot be neither created nor destroyed; it can only be changed from one form to another. This means that there must be the same number of each type of atom on each side of the equation. The atoms are simply being rearranged through the reaction process.

Chemical reactionsCombination or synthesisOften, two or more substances, that is elements combine together, to form a single substance. This type of reaction is called a combination or a synthesis, and it has only one product, for example:1. Iron (II) + Sulfur Iron (II) SulfideFe(s) + S(s) FeS(s)2. Sodium + Chloride Sodium Chloride2Na + Cl2 2NaClDecompositionDecomposition involves the reaction of a single substance by which it breaks down into two or more simple substances. Decomposition reactions have only one reactant, and are caused by either light or heat. In some reactions, a single substance breaks down into two or more simpler substances. This is called decomposition. A decomposition reaction has only one reactant, for example:1. Calcium Carbonate (limestone) (heat) Calcium Oxide+ Carbon Dioxide GasCaCO3 (s) (heat) CaO(s) + CO2 (g)2. Copper Carbonate (heat) Copper Oxide + Carbon Dioxide GasCuCO3 (s) (heat) CuO + CO23. Blue hydrate Copper Sulfate (heat) Copper Sulfate (white) + WaterCu2+(aq) + SO42 (aq) (+ H2O) CuSO4 + H2OThis reaction requires heat, in order for the reactant to dissolve. Decomposition caused by heat is called thermal decomposition.Some decomposition reactions are caused by light. For example silver chloride is a white solid. It breaks down in light to give tiny black crystals of silver, for examples:1. Silver Chloride + (through light) Silver + ChlorineAgCl2(s) (through light) Ag(s) + Cl2 (g)2. Silver Bromide + (through light) Silver + BromineAgBr2 (through light) Ag(s) + Br2 (l)3. Silver Iodide (through light) Silver + IodineAgI2 (through light) Ag(s) + I(s)Silver bromide and silver iodide decompose in the same way. These reactions are used in black and white photography. Photographic film and paper have a coating of silver chloride or bromide or iodide in gelatine. The silver compound decomposes where light strikes it, giving a dark image. The rest of the compound is washed away during processing.Precipitation Certain solutions when mixed react to product a suspension in a liquid, an insoluble product, which is a compound, and is called the precipitate. For example when aqueous solutions of sodium chloride and silver nitrate are mixed, a white precipitate of silver chloride forms: AgNO3 (aq) + NaCl(aq) AgCl(s) + NaNO3 (aq) Sodium nitrate is soluble in water, so it remains in the solution. The silver chloride precipitates because it is insoluble.Solubility All nitrates (-NO3) are soluble All acetates (CH3COO-) are soluble. All chlorides are soluble except for HgCl, AgCl, PbCl2 All sulfates are soluble except for CaSO4, BaSO4 and PbSO4 All carbonates are insoluble except for Na2CO3, K2CO3 and (NH4)2CO3 All sodium and potassium salts are soluble. All group 1 compounds are soluble. Combustion Combustion is any chemical reaction in which heat and usually light is produced, sometimes called burning.e.g. 2Mg(s) + O2 (g) 2MgO(s) + heat + white light. Combustion reactions involve the burning of a usually organic substance with oxygen. Combustion of organic substances almost always produced CO2 and H2O. Rapid combustion produces flame and high temperatures e.g. fire Slow combustion produces low temperatures and no flames. Combustion reactions are an essential part of our lives: the burning of gas, coal, petrol and oil are all combustion reactions. The heat they give out is used to cook food, warm houses and drive engines.Corrosion (rusting) Corrosion refers to the reaction of a metal with gases in the air. There are many methods to prevent corrosion such as galvanizing, chromium plating, sacrificial protection and tin plating.Other types of chemical reactions1. Oxidation:METAL + OXYGEN METAL OXIDEExamples:i. Magnesium + Oxygen Magnesium Oxide2Mg + O2 2MgOii. Iron (II) + Oxygen Iron Oxide2Fe + O2 2FeOiii. Zinc + Oxygen Iron Oxide2Zn + O2 = 2ZnO2. Metals with acids:Note: This type of reaction involves active metals such as Na, K, Hg, Ca etc. Unreactive metals such as Au (gold) do not react with hydrochloric acid (HCl), no matter how concentrated the acid is. Copper reacts with HNO3 (nitric acid). The general word equation:METAL + ACID SALT + HYDROGEN GASExamples:i. Sodium + Hydrochloric Acid Sodium Chloride + Hydrogen Gas2Na(s) + 2HCl(aq) 2NaCl(s) + H2 (g)ii. Zinc + Hydrochloric Acid Zinc Chloride + Hydrogen GasZn(s) + 2HCl(aq) ZnCl2(s) + H2 (g)iii. Aluminium + Nitric Acid Aluminium Nitrate + Hydrogen Gas6Al(s) + 6HNO3 (aq) 6Al(NO3)3 (s) + 3H2 (g)3. Acids with carbonates:ACID + CARBONATE SALT + WATER + CARBON DIOXIDEExamples:i. Hydrochloric Acid + Barium Carbonate Barium Chloride + Water + Carbon Dioxide2HCl(aq) + BaCO3 (s) BaCl2 (aq) + H2O(l) + CO2 (g)ii. Hydrochloric Acid + Zinc Carbonate Zinc Chloride + Water + Carbon Dioxide2HCl(g) + ZnCO3 (s) ZnCl2 (aq) + H2O(l) + CO2 (g)iii. Sulfuric Acid + Calcium Carbonate Calcium Sulfate + Water + Carbon DioxideH2SO4 (aq) + CaCO3 (s) CaSO4 (aq) + H2O(l) + CO2 (g)iv. Nitric Acid + Sodium Carbonate Sodium Nitrate + Water + Carbon Dioxide2HNO3 (aq) + Na2CO3 (s) 2NaNO3 (aq) + H2O(l) + CO2 (g)

4. Acids with alkalis (neutralisation):ACID + ALKALI (in equal molarity) SALT + WATER Neutralisation is an exothermic reaction, which raises the temperature of the solution.Examples:i. Sodium Hydroxide + Hydrochloric Acid Sodium Chloride + WaterNaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)ii. Calcium Hydroxide + Nitric Acid Calcium Nitrate + WaterCa(OH)2 (aq) + 2HNO3 (aq) Ca(NO3)2 (aq) + 2H2O(l)Valencies of common polyatomic ions+1123

Ammonium IonNH4+Acetate IonCH3COOCarbonate IonCO32Phosphate IonPO43

Hydrogen CarbonateHCO3Chromate IonCrO42Purple indicates that these should be known.

Hydroxide IonOHDichromate IonCr2CO72

Nitrate IonNO3Sulfate IonSO42

NitriteNO2SulfiteSO32

Valency refers to the number of electrons in the outer shell, that need to be donated or gained to make a stable shell of an ion or atom, e.g. hydrogens valency is H+, lithiums valency is Li+ and chlorines is Cl. Dont confuse with charge. Note: The elements carbon, silicon and germanium dont form ions.Chemical substancesAcidsProperties of acids Acids have a sour taste however some are dangerous as they burn. They turn litmus paper from blue to red and universal indicator red as well. There have a pH less than 7. All acids are found as solutions of pure compounds in water. Their acidity is caused by the hydrogen ions Some acids when concentrated are corrosive, which means they can eat away at metal, fabric and skin. Strong acids are acids where nearly all the acid molecules break up to form ions, for e.g. HCl. Weak acids are acids that are not corrosive, such as acetic acid which is found in vinegar. In weak acids, some of the acid molecules form ions. Strong acids always have a lower pH than weak acids. They react with metals forming hydrogen and a salt They react with carbonates forming a salt, water and carbon dioxide They react with metal oxides, forming a salt and water.IndicatorsIndicatorpH RangeInitial ColourFinal Colour

Methyl violet0-1.6yellowblue-violet

Thymol blue1.2-2.8redyellow

Bromophenol blue3-4.6yellowblue-violet

Methyl orange3.2-4.4redyellow-orange

Methyl red4.4-6.2redyellow

Litmus5-8pinkblue

Bromocresol purple5.2-6.8yellowpurple

Bromophenol red5.2-6.8yellowred

Bromothymol blue6.2-7.6yellowblue

Cresol red7.2-8.8yellowred

Thymol blue8-9.6yellowblue

Phenolphthalein8-10colourlesspink

Alizarin Yellow10-12yellowred-violet

Common acidsAcidMolecular Formula PH

acetic acidC2H4O2 (CH3COOH)2.9

benzoic acidC7H6O23

boric acidH3BO35.2

butyric acidC4H8O24.8

carbonic acidH2CO32.8

citric acidC6H8O72.2

hydrochloric acidHCl(aq)1.1

hydrocyanic acidHCN5.1

hydrofluoric acidHF2.1

lactic acid C3H6O32.4

nitric acidHNO3 1

phosphoric acidH3PO41.5

sulfuric acidH2SO4 1.2

sulfurous acid H2SO3 1.5

hydrogen sulfideH2S4.1

formic acidCH2O22.3

malic acidC4H6O52.2

arsenous acidH3AsO35

oxalic acidH2C2O41.3

salicylic acidC7H6O32.4

succinic acidC4H6O42.7

tannic acidC76H52O463.5

tartaric acidC4H6O62.2

valeric acidC5H10O24.8

BasesNeutralisation in everyday life Insect stings when a bee stings, it injects an acidic liquid into the skin. The sting can be neutralised by rubbing on calamine lotion, which contains zinc carbonate, or baking soda, which is sodium hydrogen carbonate. Wasp stings are alkaline, and can be neutralised with vinegar. Ant stings and nettle stings contain acid as well, and are neutralised with bases. Indigestion Hydrochloric acid is present in the stomach which is a very diluted, to assist with digestion. An imbalance in HCl leads to indigestion, which is very painful. Baking soda or indigestion tablets can rectify this imbalance through the process of neutralisation. Soil Treatment Most plants grow best when the pH of the soil is close to 7, otherwise the plants will not grow as well. Often, it is too acidic, so quicklime (calcium oxide), slaked lime (calcium hydroxide) or chalk (calcium carbonate), are used to treat it. These are all bases and inexpensive. Factory Waste Liquid waste from factories often contains acid. If it reaches a river, the acid will kill fish and other river life. This can be prevented by added slaked lime to the water, to neutralise it.

Properties of bases Bases are defined as being able to neutralise an acid. Alkalis are soluble substances that can neutralise acids, and remove its acidity. It does this by reacting with the hydrogen ions, forming water and a salt. Bases which are metal oxides, hydroxides, hydrogen carbonates and carbonates can also neutralise acids. Ammonia solution is also a basic solution. Bases have a pH less greater than 7, turn litmus from red to blue, and can like acids, burn skin. However, many of the bases are insoluble in water. The general reaction of acids with bases are:1. ACID + METAL OXIDE SALT + WATER2. ACID + METAL HYDROXIDE SALT + WATER3. ACID + METAL CARBONATE (or METAL HYDROGEN CARBONATE) SALT + CARBON DIOXIDE + WATERExamples:1. Magnesium Oxide + Hydrochloric Acid Magnesium Chloride + WaterMgO + 2HCl MgCl2 + H2O2. Magnesium Hydroxide + Hydrochloric Acid Magnesium Chloride + WaterMg(OH)2 + 2HCl MgCl2 + 2H2O3. Magnesium Carbonate + Hydrochloride Acid Magnesium Chloride + Carbon Dioxide + WaterMgCO3 + 2HCl MgCl2 + CO2 + H2O4. Zinc Oxide + Sulfuric Acid Zinc Sulfate + WaterZnO + H2SO4 ZnSO4 + H2O5. Zinc Hydroxide + Sulfuric Acid Zinc Sulfate + WaterZn(OH)2 + H2SO4 ZnSO4 + 2H2O6. Zinc Carbonate + Sulfuric Acid Zinc Sulfate + Carbon Dioxide + WaterZnCO3 + H2SO4 ZnSO4 + CO2 + H2O7. Copper (II) Oxide + Nitric Acid Copper Nitrate + WaterCuO + 2HNO3 Cu(NO3)2 + H2O8. Copper (II) Hydroxide + Nitric Acid Copper Nitrate + WaterCu(OH)2 + 2HNO3 Cu(NO3)2 + 2H2O9. Copper (II) Carbonate + Nitric Acid Copper Nitrate + Carbon Dioxide + WaterCuCO3 + 2HNO3 Cu(NO3)2 + CO2 + H2OProperties of alkalis Alkalis are soluble bases. Alkalis feel soapy to touch some alkalis are dangerous as they burn flesh. Their solutions turn litmus from red to blue. They have a pH greater than 7 All alkalis except ammonia will react with ammonium compounds, creating ammonia, a salt and water, e.g. calcium hydroxide + ammonium chloride calcium chloride + steam + ammoniaCa(OH)2 (s) + 2NH4Cl(s) CaCl2 (s) + 2H2O(g) + 2NH3 (g) All alkalis react with acids, producing a salt and water. Alkalis unlike bases all contain OH-1 ions, which join with the H+ ions to form water. Strong alkalis exist almost completely as ions, as solution, e.g. potassium hydroxide. Weak alkalis form ions, from some of the molecules, e.g. ammonia.Neutral substancesMany substances do not affect the colour of litmus, so are not acids or alkalis. They are neutral. Sodium chloride and sugar solutions are both neutral.

PlasticsTypes of plastics Polythene used for plastic bags, dustbins and plastic basins. Polyvinyl chloride (PVC) used for raincoats, seat covers and records Polystyrene used for plastic cups and packaging materials. Nylon used for rope, bristle for brushes, tights and clothing. Melamine used for unbreakable dishes and mugs, and ashtrays. Phenolic used for electric plugs and saucepan handles.Properties of plastics1. They are all carbon compounds2. They can be moulded into different shapes, plastic meaning easy to mould.3. The starting materials are usually obtained from oil. For e.g. polythene and PVC start off as ethene which is made by cracking some of the alkanes in oil.4. They are all polymers and consist of very long molecules, made by joining many small molecules, called monomers.Plastics are creating in the process of polymerisation. For example, ethene is reacted with hydrochloric acid to form vinyl chloride, which is mixed with warm water under pressure, and the monomers polymerise, forming PVC.Advantages of plastics Cheap, and easily made Lighter than wood, stone or metal Unreactive. They do not corrode in air or water. Many are not affected by acids or alkalis Insulators of heat, and do not conduct electricity. Able to be moulded into any shape Can be made very strong Can be made coloured, through the addition of pigments.Disadvantages of plastics Difficult to dispose of. Plastic bags and cartons do not rot when they are thrown away, so they pollute the countryside, but biodegradable plastics rot away. Some plastics catch fire very easily. When they burn, they often produce harmful gases, for e.g. PVC produces fumes of hydrogen chloride when it burns, which forms hydrochloric acid in eyes and throat. Are not as aesthetically pleasing as wood or stone.Other plastics Nylon looks shiny but does not breathe. So tactile was created, a microfibre which is thinner than nylon. Tactile has a thin layer of cotton which absorbs moisture and encourages evaporation. Viscous is made from cellulose and high absorbing of moisture. Denim is a heavy-duty cotton, which is stylistic and commonly used, but takes ages to dry and shrinks. Tensel is twice as strong as ordinary fibres, dyes well and is highly absorbent. It behaves like a cotton denim but shrinks less

Thermoplastics and thermosetting plasticsThermoplastics are plastics which get soft and runny when they are heated and hard again when they are cooled. They can be made hard and soft repeated amount of times. This is because of their structure, where the polymer chains lie next to each other. A thermoplastic gets soft on heating, because the chains can slide past each other. The soft plastic can be moulded into any shape, and the shape can easily be changed again. Some thermoplastics include Polythene, PVC, Polystyrene and Nylon.Thermosetting plastics (thermosets) only get soft once, which is the first time they are heated. Initially, the polymer chains in a thermoset are like this. When heated for the first time, it softens, and therefore can be moulded into a shape. But the heat causes bonds to form between the chains. The plastic sets firmly into its new shape. The bonds keep it hard, even when it is heated again. Examples include phenolic and melamine.AlkanesThere a three million known organic compounds. This large number is due to the fact that carbon atoms can join together easily, making chains of different lengths. The carbon atoms join by sharing electrons with each other, to form covalent bonds. Hydrocarbons are organic compounds that contain only hydrogen and carbon. Hydrocarbons can be arranged into families of compounds that are alike in some way. The simplest family of these is called the alkanes. NameChemical Formula

methaneCH4 (g)

ethaneC2H6 (g)

propaneC3H8 (g)

butaneC4H10 (g)

pentaneC5H12 (l)

hexaneC6H14 (l)

heptaneC7H16 (l)

octaneC8H18 (l)

nonaneC9H20 (l)

decaneC10H22 (l)

Methane (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10) are gases at room temperature. The boiling point increases with chain length, so the next twelve alkanes are liquids and the rest are solid at room temperature. Alkanes are found in natural gas and crude oil. Natural gas is mostly methane, with small amounts of ethane, propane and butane. Crude oil is a much more complicated mixture of hydrocarbons, and can contain alkanes with up to 100 carbon atoms in their molecules. In all alkane molecules, each carbon atom forms four single bonds. Alkanes are unreactive. For example acids and alkalis have no effect on them. However they do burn well in a good supply of oxygen, forming carbon dioxide and water vapour. The reactions give out plenty of heat, so alkanes are often used as fuels. When propane burns, the reaction is: C3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (g) + heat Both propane and butane are used as camping gas, and in gas lighters. Calor gas is mainly butane, and natural gas is used for cooking and heating in homes.IsomersSome compounds have the same formula, but their molecules have different structures. One such example is butane and methyl propane, which both have a formula of C4H10 but the butane is a chain, while the methyl propane has a branch outwards.AlkenesAnother family of hydrocarbons is the alkenes. In each of the alkene molecules above, each carbon atom forms four bonds, of which one of them is a double bond between carbon atoms.Alkanes also burn in oxygen like alkanes, and have very similar chemically properties. e.g. C2 (g) + 3O2 (g) 2CO2 (g) + 2H2O(g) + heatHowever, alkanes are unreactive compounds, but alkenes are not, reacting with hydrogen and other compounds.e.g. C2H4 (g) + H2 (g) C2H6 (g)Alkenes are more reactive than alkanes. The double bond within carbon atoms can break to form single bonds, so can combine easily with other elements such as Hydrogen or Oxygen. This reaction is called combination or synthesis. Ethene is unsaturated (not full) since its molecules can add on more atoms, while ethane is saturated (full), since its molecules cannot fit in more atoms because there are no double bonds to break, and each carbon atom already has four single bonds. Testing for unsaturationThere are two ways of testing a hydrocarbon to determine whether it is an alkane or alkene.1. The addition of bromine water. Bromine water is an orange solution of bromine in water. It turns colourless in the presence of an alkene, because the bromine adds on to the alkene, to form a colourless compound:C2H4 (g) + Br2 (aq) C2H4Br2 ethane + bromine water 1,2-dibromoethane2. The addition of potassium manganate. This is purple, but turns colourless when an alkene is present.PolymerisationAlkene molecules can combine with each other, due to their double bonds in a process called polymerisation. During polymerisation, many small molecules, called monomers, join together to from very large molecules, called polymers. Polythene is an example of such a molecule which is formed by this process. It is formed, when ethene is heated, under high pressure. More than 1,000 ethene molecules can combine through this process to make a single molecule of polythene. Polythene is a solid. It is unreactive, as there are no double bonds present. It can be rolled into thin sheets and moulded into different shapes, and because that is easy to mould, it is called a plastic.RadiationSome atoms have more or less neutrons in their nucleus than usual and become unstable. The nucleuses of these atoms break down or decay. When this happens, the nucleus will emit radiation in the form of high kinetic energy charged particles or EMR. Also, the atomic and mass number of the atom changes and so a new element is formed.Three types of nuclear radiation are released:1. Alpha particles: are helium nuclei (2 protons & 2 neutrons) have a high ability to ionise biological matter can be stopped by a few centimetres of air, a sheet of paper2. Beta particles: Are electrons Travel several metres through air Stopped by sheet of A1 paper or 1 cm layer of wood3. Gamma rays: High frequency, high energy electromagnetic waves Not very ionising Can travel kilometres through air Can be stopped by more than 2-3 cm of lead

BiologyReproductionAsexual reproduction Suckers When a plant is burnt or cut down, small stems can grow from the base of the stump. The small stems, referred to as suckers, and can grow into new trees. Runners Some plants reproduce by sending out a side branch along the ground that is called a runner. Along the runners are nodes or joints. New roots or shoots can grow at these points. Later, the connecting runners may rot away, leaving separate plants. Rhizomes are a stem of the plant underground, often sending out roots or shoots, if a rhizome separates, the fragments form new plants. Sexual reproductionThe reproductive systems and hormones Fallopian tubes (oviduct): The fallopian tubes (oviduct) connects the ovaries to the uterus (womb). The fallopian tube is also where the egg is fertilized by any sperm. Uterus (womb): The uterus (womb) is where the egg develops. Ovaries: The ovaries are responsible for the production of the female sex hormones oestrogen and progesterone. Placenta (afterbirth)The placenta is the link to between the mother and the baby. Zygote, embryo and foetus: The zygote is the newly fertilized ovum (egg). The zygote travels down the fallopian tube (oviduct) to the uterus (womb), where it grows inside a hollow ball of cells called a blastocyst. The embryo is the growing baby during the first two months, after the first two months, the embryo is referred to as the foetus, as development of sex organs start to take place. Oestrogen and progesterone: Oestrogen is one of the female hormones, and progesterone is the other female hormone. They both produce the various secondary sexual characters of females. Scrotum: The scrotum is a pair of sacs which hang separate from the body. The scrotum contains the testes which produces the male hormone of testosterone. The scrotum hangs from the body as the production of sperm require a temperature of 35C. Prostate: The prostate is a gland that produces the thick milky alkaline fluid for the sperm to swim in, which neutralises the acid of the vagina, which would otherwise kill the sperm. Seminal vesicle: The seminal vesicles are a pair of glands which produce a fructose (sugar in fruits) fluid that provides food for the sperm. Vas deferens (sperm duct): The vas deferens (sperm duct) stores the sperm, until it is ready for use. Epididymis: The epididymis are the thicker tube made up of the smaller sperm-producing tubes. Urethra male vs. female: The urethra in a male goes through the penis, and carries sperm and urine to the outside, in a urethra in females carries urine from the bladder to an opening near the vagina. Testosterone: Testosterone is the male hormone which stimulates the secondary sexual characteristics.

"Normal" cell division maintains the same number of chromosomes and is called mitosis. In the type of division called meiosis the chromosome number is halved. The only two organs in which meiosis occurs are the testes and ovaries.

Reproduction in humans (including puberty) For the first 9 weeks after conception all babies are female. After this time, if the baby is going to be a boy, the hormone testosterone is produced stops the growth of the female sex organs. The onset of puberty is controlled by the pituitary gland. Puberty lasts 6-7 years and begins in girls at age 10-12 and in boys at age 11-12. Boys have a growth spurt from ages 13-16. The female hormone made in the ovaries is called oestrogen. Secondary sex characteristics showing the change of girls into young women include: pubic hair development, growth of breasts, changes in bones (especially hips), fat distribution to hips and thighs and development of sexual desires. Another name for periods is menstruation. It lasts for about 5 days and involves a loss of 0.1 litres of blood which comes from the breakdown of the uterus wall. Sperm cells are made in the testes. The testes also produce the male hormone called testosterone. Secondary sex characteristics showing the change of a boys into young men include:larger face, growth of body and facial hair, increased muscle development, thickening of vocal chords (deepening of voice), skeletal changes, fat distribution to the abdomen, stimulation of sweat and oil producing glands.Reproductive system in plants - flowers Petals are used to attract insects to the flower; they may guidelines on them and may be scented. Especially in the case of bees, which can see a lower range of the light spectrum and also part of UV light which humans cannot see can be present on flowers. Stigma is covered with a sticky substance that pollen grains will adhere to. The style raises the stigma away from the ovary to decrease the likelihood of pollen contamination. It varies in length. The nectary is where the sugary solution called nectar is held to attract insects. From this nectar, honey is made. The ovary protects the ovule and once fertilisation has taken place, it will become the fruit, which becomes food for various animals. The ovule is like the egg in animals and humans, and once fertilization has taken place, it will become the seed. The receptacle is the flowers attachment to the stalk and in some cases becomes part of the fruit after fertilization e.g. strawberries and tomatoes. The flower stalk gives support to the flower and elevates for insects. The flower is formed on the stalk, using glucose formed in the leaves of the plant. The flower starts as a bud, then opens to reveal its petals, anthers and stigma. While the flower is developing from a bud, the sepal protects it. The filament is the stalk of the anther. The anthers contain pollen sacs. The sacs release pollen on to the outside of insects such as bees, on entering the flower. The pollen then deposited, is transferred to the stigma of another flower or the same flower. The ovule can now be fertilized, and the plant can continue to survive as a species. The ovule, stigma and style are known together as the carpel or female parts of the flower. The filament and the anthers are collectively known as the stamen or the male parts of the flower.The brain and communications in the human bodyThe communications systems in the human body are the nervous system and the endocrine system. They act together to co-ordinate the body, maintaining humans as functioning organisms. Both systems incorporate feedback mechanisms, to modify their response to changing circumstances, especially change instigated by the system. The central nervous system (CNS) consists of the brain and spinal cord. The brain is responsible for most control and all conscious thought. The spinal cord is responsible for information dissemination to peripherals and for the reflex arc.The nervous systemFunction: The nervous system of our body and control and coordinates all parts of the body. The nervous system is the most complex and least understood of all our body systems. It consists of two main parts: The Central Nervous System (CNS) and the Peripheral Nervous System (PNS) The CNS is made up of the brain and the spinal cord.The Central nervous systemThe CNS is the control centre and receives messages from all parts of the body. After receiving this information, the brain examines it and sends instructions to different parts of our body about the action they must take.The Peripheral nervous systemThe PNS is made up of sensory receptors and nerves which continuously inform the CNS of the changing conditions, and transmits the decisions taken by the CNS back to the effector organs such as muscles and glands.Parts of the nervous systemReceptorsReceptors are the end of a nerve, which are sensitive to certain stimuli in the environment of an organism such as heat, touch or light and responds to stimuli by transmitting to the CNS the information. Some receptors include: Taste receptors (taste buds) receptors located on the tongue which are sensitive to different chemicals, such as acids, sugars or salts. Olfactory receptors receptors located in back of the nose, which are sensitive to smells and odorants. Trigeminal nerve receptors receptors located also in the back of the nose, are responsible for touch, pressure, pain and temperature sensations in the mouth, eyes and nasal cavity. Photoreceptors (light receptors) receptors located in the retina of the eye, called rods and cones. Rods are responsible for black and white colour, brightness and darkness, and night vision. Cone cells are responsible for colour vision, but require bright light.EffectorsAn effector is the muscle, gland or organ cell capable of responding to a stimulus at the terminal end of a efferent neuron or motor neuron. They are responsible for the actions, in response to the environment of the organism: Muscles contract and relax, to produce movements. Glands, which are part of endocrine system, release chemicals called hormones which have an effect on the organisms actions.NeuronsNeurons are nerve cells, responsible for the transmitting of information between the receptors and the CNS, and the CNS and the effector. Sensory neurons carry information from the sensory receptors to the CNS. Receptors, when stimulated, send of electrical pulses along the sensory neurones to the CNS. Motor neurons carry information from the CNS to the effector, such as a muscle or gland. They carry electronic pulses which contain within the message from the CNS to the effector, regarding the movement by the muscle, or release of hormones from glands. Motor neurons and sensory neurons are not directly connected. Connector neurons (association neurons), found with the CNS to allow movements and release of hormones, by completing the transmission of information from the receptor to the effector. NervesNerves are cable-like bundles of the axons of neurones, in the peripheral nervous system. A nerve provides a common pathway for the impulses to travel along the axons (fibres) to the peripheral organs. Afferent nerves conduct signals from sensory neurons to the central nervous system. Efferent nerves conduct signals from the CNS along the motor muscles to the effectors. Mixed nerves conduct signals both to and from the central nervous system. Spinal nerves connect to the spinal cord. Cranial nerves connect directly to the brain, especially the brainstem. One such example is the optic nerve.Multipolar neuronsMultipolar neurons are a type of neuron that has one axon, but multiple dendrites, which means they are able to take in a lot of information. They constitute the majority of neurons located in the brain, and include motor neurones and connector neurons (interneurons).Bipolar neuronsBipolar neurons are a type of neuron that has two extensions, acting as specialised sensory neurones, for the transmission of special senses. They are used to transmit motor signals to control muscles. They are also present in the eye, as retina bipolar cells, which are located between the photoceptors (rods and cones) and the ganglion cells (another neuron cell type that takes the input from the photoceptors)SynapseNeurons are not connected, there a small expanse between them. The electrical message is converted into neurotransmitter chemicals which are released at the end of the axon which stimulates the dendrite of the receiving neuron.Parts of a neuron Cell body:The cell body contains a nucleus and supplies energy and nutrients for the activity of the neuron. Axon: The axon is a long structure through which the nerve impulse passes from the cell body, which branches at the end, is covered by myelin. Dendron: A dendron is one of the several cytoplasmic processes (projections) arising from the cell body of a neuron. It carries impulses towards the cell body. Dendrites: Dendrites are the branched projections of a neuron that conduct the electrical impulse which travels along the neuron. Dendrites also receive information from other cells. Myelin: Myelin is an insulating layer around nerves including those in the brain and spinal cord, and is made up of protein and fatty substances. Myelin allows impulses to transmit quickly and efficiently along the nerve cells. When it is damaged, diseases such as multiple sclerosis can result.The process of sending an impulseWhen an impulse reaches the axon terminals, it causes chemical compounds called neurotransmitters to be released into the synapse. The neurotransmitters alter the chemical surroundings of the next neurons dendrites significant enough that this change is detected, and the next neuron fires, and the impulse continues along the next neuron. The speed with which information is carried by neurons and nerves is between 1-100 ms-1. Messages travel as electrical pulses. The central nervous system consists of the brain and the spinal cord The peripheral system consists of all the nerves that connect to the central nervous system. Sensory and effector nerve cells have a long tail like structure called an axon. The gap between two neurons is called a synapse.The BrainThe Brains protectionThe brain is well protected within the skull, and is also covered with three layers of a connective tissue called meninges, and is also surrounded by cerebral fluid that cushions the brain against bumps and knocks.Parts of the brainThe brain is made up of about 80% water, 10% fat, 8% protein and small amounts of other substances. The brain is also made up of one hundred billion cells and is the most complex organ in your body. The brain will grow to the size of large grapefruit, and weighing 1.5 kg. The size, weight of the brain and the learning connections between cells in your brains differs between people due to experiences.

The human brain consists of: The cerebrum makes up 90% of the brains volume and is composed of two hemispheres, which appear grey due to the large amounts of grey matter (cell bodies of interneurons) and small amounts of white matter (the myelin sheath that protects the axons). The cerebrum controls memory, speech and though. All conscious actions, such as walking, running and speaking are controlled in this area of the brain. The cerebellum is located towards the back of the brain, underneath the cerebrum, where the skull curves inwards. The cerebellum is pink in colour, and is responsible for balance and co-ordination of complex muscle actions. The brain stem (medulla) controls the activities such as heart rate, breathing and digestion. It also controls unconscious or involuntary thoughts. The brain stem also connects to the spinal cord. The limbic system is one of the other parts of the brain and contains the thalamus, the hypothalamus, and the hippocampus. It is located at the top of the brain stem. The thalamus is the gatekeeper for messages passed from the spinal cord to the cerebrum. The hypothalamus controls emotions, and regulates temperature by telling the body to sweat when overheated, and to shiver when cold. The hippocampus sends memories to be stored in sections of the cerebrum, and then recalls them when necessary. The pituitary gland (see Endocrine System) is the main endocrinal organ. It has three lobes and produces several hormones (most stimulate other glands in the body). The pituitary gland is located at the base of the brain and is connected to the hypothalamus by nerve fibres.The brain and stimulus sight Sight is a complex function of the brain that extends from the front to the back of the head. Sight is produced through the eyes capture information, and is send through the optic nerve to the brain. The brain also incorporates other sensory stimuli, to result in the application of sight, such as picking up an object. Problems with sight may occur due from damage to certain parts of the brain.Optic nerveAn image is created when light reaches the retina located at the back of the eye. This image is then sent along the optic nerve to the brain. The optic nerve (second cranial nerve) connects the eyes with the brain. The optic nerve crosses at the optic chasm which explains why information from the eye is sent to the opposite side of the brain.Occipital lobeThe occipital lobe is one of the specific parts within the brain that processes sight, and is located at the back of the brain. Each hemisphere has its own occipital lobe, which processes all sight-related information sent to that hemisphere. The occipital lobe, if damaged, may result in visual field cuts, and problems identifying colour or movement of an object. This is because the occipital lobe controls a persons perception of sight.Visual cortexThe visual cortex is the part of the brain where sensory and motor information is integrated with vision, and is located within the occipital lobe. Multiple visual pathways are involved in the processing of the information, for example: The dorsal visual pathway controls a persons visual motor response to objects. The ventral visual pathway controls how a person identifies an object.The brain and stimulus hearing Hearing is the function of the brain that is heavily linked and involved with language. When sound information is processed in the language centres of the brain, it allows the person to understand what is being heard. Hearing is also connected to music, through identification of sounds and tones.The earsThe ears gather the stimulus needed by the brain to process in order to produce hearing. The ear is made up three parts: The Outer Ear (pinna) collects sounds vibrations. The Middle Ear contains small bones called the ossicles, which convert the sound vibrations into mechanical vibrations. The Inner Ear contains the Organ of Corti, a sensory receptor, located within the cochlea, which has hair cells which are the nerve receptors used for hearing.Acoustic nerveThe sound information is passed from the ears to the brain by the acoustic nerve (eighth cranial nerve). The acoustic nerve splits into two pathways (one to each hemisphere), allowing each hemisphere to hear information from both ears.Temporal lobeThe hearing processing centre of the brain is the temporal lobe, which is located near the ears. The temporal lobe in the left hemisphere is the language part of the brain, and is responsible for comprehension and understanding what someone is saying. The temporal lobe in the right hemisphere is the musical part of the brain, and is responsible for the identifying of musical inform