P2: Living for the Future Key points for revision (Higher)

P2: Living for P2: Living for the Futurethe Future

Key points for revision Key points for revision (Higher)(Higher)

Energy from the SunEnergy from the SunThe Sun• is a stable source of energy• transfers energy to the Earth as light

and heat• is a renewable source of energy

Energy from the SunEnergy from the SunThe Sun’s energy can be collected:• by photocells• by being absorbed by a surface and

transferred into heat energy• from convection currents that cause

the wind to blow and to transfer kinetic energy to electricity in a wind turbine

• by passive solar heating

PhotocellsPhotocells• transfer light into electricity• produce direct current (DC)• can operate in remote locations• produce more power when there is:1. a brighter light2. and a bigger area of cell exposed

Advantages of photocellsAdvantages of photocells• low maintenance• no need for power cables• no need for fuel• long life• rugged• use renewable energy resource• no polluting waste

Disadvantages of photocellsDisadvantages of photocells• No power at night• No / low power in bad weather

How a photocell worksHow a photocell works• energy is absorbed by the photocell• electrons are knocked loose from the

silicon crystal• the electrons flow freely in an electric

current

How passive solar heating How passive solar heating worksworks

• short wavelength infrared passes through the transparent glass

• the bodies inside absorb the infrared• the bodies emit long-wavelength

infrared• the long-wavelength infrared cannot

pass through the glass, so the glass reflects it back into the room

Advantages of wind turbinesAdvantages of wind turbines• use renewable energy• rugged• no chemical pollution

Disadvantages of wind Disadvantages of wind turbinesturbines

• will not work when there is no wind• can not work when it is too windy• make a visual impact on the

landscape• take up a lot of land

Generating electricityGenerating electricity

• Batteries produce direct current (DC)• Generators produce alternating current

(DC)A generator can produce more electric

current:1. by using a stronger magnet2. more coils of wire3. moving the magnet or coils faster

Generating electricity in a Generating electricity in a power stationpower station

• Fuel is burned• producing steam• spinning a turbine• causing the turbine to turn the

generator

• A lot of energy is transferred to the environment in the form of heat

TransformersTransformers• Increase or decrease voltage• A higher voltage means a lower

current so less energy is wasted in heating the electric cables

Energy equationsEnergy equations

• fuel energy input = waste energy output + electrical energy output

• efficiency = electrical energy output

fuel energy input• efficiency = little number

big number

Fuels in power stationsFuels in power stations

• Fossil fuels: oil, coal, natural gas• Renewable biomass: wood, straw,

manure• Nuclear fuel

• All fuels release energy in the form of heat

EquationsEquations

• power = voltage x current• (watts) (volts) (amps)

• energy = power x time• (kilowatt-hours) (kilowatts)

(hours)

RadioactivityRadioactivity

• Ionising radiations from radioactive waste can cause cancer

• Uranium is a non-renewable fuel• Plutonium1. is a waste product from nuclear

reactors2. can be used to make nuclear bombs

Advantages of nuclear Advantages of nuclear powerpower

• No fossil fuels used• Plenty of uranium available• No greenhouse gases

Disadvantages of nuclear Disadvantages of nuclear powerpower

• High decommissioning costs when a nuclear power station is finished with.

• Pollution from fuel processing.• Risk of radioactive leak.• High maintenance costs.

Background RadiationBackground Radiation• Background radiation is around us

all of the time• Background radiation comes from:1. rocks & soil2. cosmic rays

Nuclear RadiationNuclear Radiation

• Alpha can travel a few cm in airis stopped by paper

• Beta can travel about a metre in airis stopped by a few mm of aluminium

• Gamma can travel a very long way in airis reduced by a few cm of lead

Radioactive SafetyRadioactive Safety

• Wear protective clothing• Use tongs; don’t touch sources• Keep sources at a sensible distance• Use radioactive materials for short

amounts of time• Label & store the sources carefully

Uses of radioactivityUses of radioactivity

• Alpha-smoke detector• Beta-controlling paper thickness;

tracers• Gamma-treating cancer; sterilising

equipment; tracers

Radioactive WasteRadioactive Wastecan be disposed of:1. in land-fill sites if it is low-level

waste2. by encasing it in glass and storing it

underground3. by reprocessing

Radioactive WasteRadioactive Waste• remains radioactive for a long time• is at risk from terrorism• must be kept out of water supplies

IonisationIonisation

When Alpha or Beta particles pass another atom, they tend to pull electrons off it.We then say that the atom is ionised. If it has lost electrons, we call it a positive ion.

An atom is ionised if it gains or loses electrons

Magnetic fieldsCurrent-carrying coilBar magnet

Earth’s Magnetic Field

Magnetic South pole

Magnetic North Pole

Cosmic RaysCosmic Rays

• are fast-moving particles, which create gamma rays when they hit the atmosphere

• spiral round the Earth’s magnetic field to the poles

• cause the Aurora Borealis

How the Moon was formed

How the Moon was formedHow the Moon was formed• Two planets collided• Their iron cores joined together to

form the Earth• Some less dense material broke off

and became the Moon, orbiting the Earth

Uses of satellitesUses of satellites• Telecommunications• Weather forecasting• Spying• Satellite navigation

The SunThe Sun• is a source of ionising radiation• produces solar flares – which:• are clouds of charged particles• are sent out at high speed• produce strong magnetic fields• affect satellite communication• affect electricity distribution

The Solar System

GravityGravity• Every body that travels in a circle

does so because it is acted on by a force towards the centre of the circle, called the centripetal force

• Gravity provides the centripetal force

The UniverseThe Universeconsists of:• stars• planets• comets• meteors• black holes• large groups of stars called galaxies

Light-yearLight-year

• The universe is so big that a way of measuring very large distances is needed

• One light-year is the distance travelled by a beam of light in 1 year

Problems of manned Problems of manned spaceflightspaceflight

• Need huge amounts of fuel• Need large quantities of food and water• Journeys can take many years• Low gravity can affect health• Cosmic rays can be harmful• Must maintain a stable atmosphere• Must maintain suitable temperature

Unmanned spacecraftUnmanned spacecraft• can withstand conditions that are

lethal to humans• can send back information on:

• temperature, magnetic field & radiation

• gravity, atmosphere and surroundings

Unmanned spacecraftUnmanned spacecraft

• don’t put human lives at risk• are cheaper than manned craft• are difficult to maintain because there

is no one to carry out repairs and maintenance

AsteroidsAsteroids can:

cause craters

throw up hot rocks

cause fires

create dust which blocks out sunlight

cause climate change

make species extinct

AsteroidsAsteroids• are rocks left over from the formation

of the Solar System• orbit between Mars and Jupiter• have not joined together to make

another planet because the large gravitational field of Jupiter has prevented this from happening

Evidence for past asteroid Evidence for past asteroid collisionscollisions

• Craters• Unusual elements in rock layers• sudden changes in fossil numbers in

layers of rock that are next to one another

CometsComets• are made from ice and dust• have highly elliptical orbits• come from deep space, beyond the

planets• travel faster as they approach the

Sun because the gravitational force gets stronger

Near-Earth Objects (NEOs)Near-Earth Objects (NEOs)• are asteroids or comets that could

collide with Earth• are watched through telescopes• tracked by satellites• could be knocked off course by

explosions if necessary

The Big BangThe Big Bang• The Universe started with an

enormous explosion called the Big Bang

• The Universe is still expanding

Evidence for the Big BangEvidence for the Big Bang• Red shift shows that all galaxies are

moving away from us• Red shift shows that distant galaxies

are moving faster than closer ones• Microwave radiation is detected from

all parts of the Universe

Stars are bornStars are born• when clouds of gas and dust• are compressed by huge gravitational

forces to form a protostar• the huge rise in temperature causes

fusion to occur and hydrogen atoms join together (fuse) to make helium atoms, giving out massive amounts of energy

When medium-weight stars When medium-weight stars diedie

• they swell up to form a red giant• they throw out shells of gas called a

planetary nebula• shrink to form a white dwarf• cool to form a black dwarf

When heavy-weight stars When heavy-weight stars diedie

• they swell up to form a red giant• the core collapses and the whole star

explodes in a supernova• leaving behind a dense neutron star• sometimes the neutron star collapses

to form a black hole, which is so dense and has such a large gravitational field that not even light can escape

WelcomeWelcome

To TIPS To TIPS

to doing well in your to doing well in your

B2 Science Examination!B2 Science Examination!

•T. . . Trinity•I . . . Improves•P . . . Pupil•S . . . Success

•You have attended the lessons

•You have completed the revision

•Now let’s have a few reminders about exam technique

Firstly the BIG QUESTION . . . Why do we have to do exams?

You have to give the examiner the proof that you have done the lessons and learnt lots of Science.

This is your chance to demonstrate this.

• On the exam paper will be a range of questions that cover the different topics e.g. collecting information on what lives where ( ecology) or how to increase photosynthesis (food factory) etc.

• Some questions will be easy and you will all get those correct and some will be really challenging to stretch the very best of you.

• Check out how many marks are for each question

•So, you have had the breakfast, and you are about to do your best.

•Even now there are teachers around to help you, and during the exam the invigilators will make sure the whole process is as painless as possible.

•Your lessons have covered 8 topics and there will be 5 questions so you cannot be asked about everything. It will be your good luck if you are asked questions about your ‘best bits’!

•Let’s have a look at the style of question.

EcologyEcology• They often ask you a calculation here,

that’s why we use calculators!

• Look carefully at the DATA they give you and work out the average (mean)

• They usually want you to be critical about the data – is there ENOUGH of it?

EcologyEcologyquadrat number of

dandelions

1st 5

2nd 1

3rd 0

4th 2So, 5 + 1 + 0 + 2 = 8. To find the average you divide by the number of samples,

so 8 ÷ 4 =2 for each quadrat

Critical comment ‘small sample size’

From Jan 08

Grouping OrganismsGrouping Organisms• This involves classification, lots of

different groups, e.g. plants and animals, vertebrates and invertebrates etc.

• They like to ask about distinguishing features for a particular group.e.g. what are two features that only mammals have? FUR and MILK to feed the young

Grouping OrganismsGrouping Organisms• Lions and cheetahs are different species

What is meant by the term species? (2 marks)

. . . . These are organisms that can successfully reproduce (breed, mate) (1)

AND . . . . The offspring are also fertile (1)From Jan 07

The Food FactoryThe Food Factory• You have the knowledge THE

EQUATION . . .

water + carbon dioxide glucose + oxygen

From Jan 08And as the balanced formula

6 H2O + 6 CO2 C6H12O6 + 6O2

From Jan 07

The Food FactoryThe Food Factory• Photosynthesis is a special process

done by only green plants

• Remember it is linked to that other essential living process done by EVERY CELL . . . called . . . RESPIRATION, that releases energy!

The Food FactoryThe Food Factory• What are the 3 conditions that help

and sometimes limit photosynthesis

. . . . more LIGHT

. . . . higher TEMPERATURE

. . . . more CARBON DIOXIDE

Compete or DieCompete or Die• Successful PREY are found in large

enough numbers so that some will survive!

• Successful PREDATORS raise more offspring

• Remember plants are busy competing as well, for? spacelight waterminerals

Compete or DieCompete or Die• The farmer gets fewer weeds in his

bean fields than in his wheat fields. Suggest why. (1 mark)

. . . . . not enough minerals for weeds OR more competition for light OR more competition for water OR more competition for minerals

From Jan 08

Adapt to FitAdapt to FitWhen you have got masses of living things in one place, any individual that is better suited will do better, breed better etc.Gradually the features that are better suited become more common.Eventually you get a specialised organism that perfectly matches it’s habitat. e.g. polar bears in the Artic

Adapt to FitAdapt to Fit• Camels are adapted to live in the desert,

what are the ways they are adapted . . . .(3 marks) From Jan 07

fat in hump (1), long eyelashes (1), large feet (1), to stop sand getting in eyes (1)for food store (1), to spread out load (1) etcMake sure you write enough to get all 3 marks.

Survival of the FittestSurvival of the Fittest• Fossils are the remains of extinct

animals, suggest why the rest of the animal did not fossilise . . . . (1 mark) from Jan 08SUGGEST questions mean you can give any SENSIBLE solution. Many answers allowed such as:- too soft, decayed, decomposed, was eaten, biodegraded, rot, no bones, not hard.

Survival of the FittestSurvival of the Fittest• Describe how fossils are formed from

shells. (1 mark) from Jan 08DESCRIBE questions must tell the story clearly, so the examiner knows you have learnt the processes involved.Possible answers: covered in sediment (1), empty shell filled with deposits (1), replaced by minerals (1)

Survival of the FittestSurvival of the FittestDarwin’s Theory of Natural Selection

1. Sexual reproduction leads to variation

2. Organisms with successful characteristics survive

3. Survivors breed passing on the characteristic in the genes

4. Over many generations organisms evole

Survival of the FittestSurvival of the Fittest• For Example • Imagine a large group of grazing animals,

all showing variation (slightly different to each other)

• Some individuals happen to have longer necks.

• They reach fresh food supplies, and they are more successful so breed

• The long neck genes get passed on• Longer necked individuals eventually

become a new species e.g. giraffes!

Population out of ControlPopulation out of Control• This covers all the consequences to our

planet of us having such a large population e.g. acid rain, holes in the ozone layer, global warming etc.

• Indicator species reflect the damage doneagain you might have to read and answer questions based on DATA given.

Read it through more than ONCE.

SustainabilitySustainability• This covers all the ways we are trying to

put right the damage our large population is causingBlue whales are an endangered species, they are hunted because their bodies had many commercial uses. What was one commercial use . . . . (1 mark)food OR oil OR cosmetics OR glue

SustainabilitySustainability• Many people think that hunting of all types

of whales should stop. Why is it difficult to stop all whale hunting? (1 mark) from Jan 08

It is difficult to enforce OR seas to large to patrolOR not clear which country is responsible for different parts of the sea.

•Good Luck•You have got the

knowledge •You have got the

skills•Now get the marks

B2 Exam Revision

Paints.Paints.• Paints contain:

– Pigment (gives it colour).– Binding medium (glues it to the wall).– Solvent (stops it sticking to the inside

of the tin.)

Paints.Paints.• Paints are colloids:

– Tiny particles mixed (NOT dissolved) in a liquid.

– Don’t separate because they’re so small.

Dyes and special paints.Dyes and special paints.

• Dyes used to be made form plants but now they are synthetic (man made).

• Thermo chromic paint:– Changes colour with heat.

• Phosphorescent pigments:– Absorb light energy, store it in their

molecules, and then release it.– In the olden days they were radioactive.

Construction materials.Construction materials.

• Cement is made from clay and limestone.– Add gravel and it makes concrete as well.– Reinforcing with iron bars like the twin towers

makes it a ‘composite material’.• Better to take sudden shocks like planes hitting

them, but the metal can rust or melt and cause problems.

Construction materials.Construction materials.

• Glass is made by melting Limestone, sand, and soda.

• Metals are extracted from ores.

• Bricks are made from clay just like your mug of tea in the morning.

Electrolysis.Electrolysis.• Electrolysis is splitting things up using

electricity.

• At the positive (+) anode electrons are lost as the copper atoms dissolve to form copper ions.Cu(s) ==> Cu2+(aq) + 2e-

Electrolysis.Electrolysis.• An electrolyte is a conducting melt or

solution of ions which carry the electric charge as part of the circuit.

– Like copper sulphate allowing the copper ions to float across.

• At the negative (-) cathode electrons are gained by the attracted copper(II) ions to form neutral copper atoms.Cu2+(aq) + 2e- ==> Cu(s)

Copper purification.Copper purification.

Extraction of aluminium.

siphon

Graphite / carbon anodes

Molten aluminiumMolten electrolytebauxite + cryolite

Tanklinedwith

carboncathode

Moltenaluminiumout

Steelcase

Vented cover

Alloys.Alloys.• An alloy is a mixture of a metal and

any other element.

• Steel is an alloy of Iron and carbon, it can now absorb impacts better.

• Don’t forget brass, bronze, solder, and amalgam.

Different types of rock.Different types of rock.

• Sedimentary:– Soft crumbly, made from bits squished

together. E.g. limestone.


• Metamorphic:– Made by heat and pressure on sedimentary

rocks, for long times. E.g. Marble.– Eventually they will melt and turn into

magma.


• Igneous:– Magma below ground, Larva above ground.– Intrusive = slow cooling = large crystals =

underground.• (Basalt.)

– Extrusive = fast cooling = small crystals = above ground.• (Granite)

Don’t forget the currents in the magma moving the plates.

The structure of the The structure of the EarthEarth

• Crust:– Relatively thin and cool outer layer of the

Earth. – It is much cooler, harder, brittle and less

dense than the other layers.– Divided into sections or 'plates' which 'float'

and move on the mantle.


• Mantle:– Almost solid but can move very slowly as

huge convection currents from radioactive decay in the core.

– It is relatively cold and rigid just below the crust, but lower down it is much hotter and non-rigid and so is able to flow.• Same thickness as Jam.


• Core:– Mainly of iron, and nickel.– Its diameter is about half that of the Earth

(3500 km radius) and its is very hot and dense.

– Consists of an outer liquid layer and a solid inner layer.

– Heat is generated by radioactive decay.– The mainly iron core generates a magnetic

field through and around the Earth.


• The lithosphere is the rigid, relatively cool crust, and the outer or upper part of the mantle. It is split into sections called plates.

Plate tectonicsPlate tectonics• Plates used to ‘jigsaw’ fit together.

– used to form Pangaea.

• Fossils match on opposite sides of the oceans

• Identical rock sequences all around the world.

• Plates moved by slow convection currents in the mantle.

Subduction of the oceanic Subduction of the oceanic plate, under the continental plate, under the continental

plate.plate.

• Notice the mid ocean ridge, the costal earthquakes, and the costal ‘spine’ of volcanoes.

VolcanoesVolcanoes

• Formed by molten rock cooling as it surfaces.

• Subduction of oceanic crust can cause volcanoes as well.– Also cause earthquakes.

• Volcanoes make igneous rocks.– Runny lava is safer as you can run away form

it.– Sticky lava forms bombs and volcanoes

explode.

How we got air we can How we got air we can breath.breath.

1. Volcanoes give out steam and CO2.• Steam later condensed as rain (for

centuries).• A billion years


2. Green plants take CO2 in and produce O2.

• Forms fossil fuels.• Nitrogen gas is put into the air by bacteria


3. Ozone layer forms.• Blocks out UV rays.• Complex organisms evolve.

• 78%N2; 21% O2; 0.035% CO2

Life is all about cycles.Life is all about cycles.• Water.• Nitrogen.• Rocks.• Carbon.

Air pollution and acid rain.Air pollution and acid rain.• Acid rain;

– Made from sulphur dioxide and oxides of nitrogen, (sulphuric acid and nitric acid).

– Kills fish and plants, (so no food for other things to eat).

Air pollution and acid rain.Air pollution and acid rain.• Catalytic converters take Nitrogen

oxide out of car fumes but replace it with carbon dioxide.

– 2CO + 2NO → N2 + 2CO2

– poison + acid rain → harmless + global warming.

Air pollution and acid rain.Air pollution and acid rain.• CO2;

– Increases global temperature, by stopping the heat from escaping.

– More heat means more evaporation which means more rain.•Hot places are getting hotter.

– (droughts, and famines)•Wet places are getting wetter.

– (floods.)

Collision theory.Collision theory.• Reaction only happen when things

collide.• Higher rate of reaction means ‘an

increase in the number of successful collisions.’

• More collisions means more likely hood of a successful one happening.

• Faster / harder collisions make each collisions more successful.

Temperature.Temperature.• Temperature is a measure of the

kinetic energy of the particles in an object.

• Increasing the temperature makes the particles move faster.

• Faster collisions means more likely to react.

ConcentrationConcentration(or pressure in gases).(or pressure in gases).

• Particles more crowded together.• More collisions.• Higher likelihood of a successful

collision happening.

Powder / lump.Powder / lump.Surface area.Surface area.

• More of the particles CAN hit each other at any time.

• (Granulated sugar and a lump of sugar)

Catalysts.Catalysts.• Decrease the amount of energy

needed for a reaction to successfully happen.

1. Catalysts must not be changed or used up by the reaction.

2. Only work for certain reactions.

Rates.Rates.• Speeding it up.1. Heat it up.2. Make it more

concentrated / pressurised.

3. Increase the surface area (make it a powder).

4. Add a catalyst.

• Slowing it down.1. Cool it down.2. Make it less

concentrated / pressurised.

3. Decrease the surface area (make it a lump).

4. Don’t add a catalyst.

Rate = volume of gas produced time taken.

Documents

P2: Living for the Future Key points for revision (Higher)