aqa science gcse sca2hp notes

8/22/2019 Aqa Science GCSE SCA2HP notes

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6/2/2013 3:01:00 AM

C1.5 - Other useful substances from crude oil

Fractions form crude oil can be cracked to make smaller molecules, including unsaturated

hydrocarbons such as ethane. Unsaturated hydrocarbons can be used to make polymers

and ethane can be used to make ethanol. Ethanol can also be made from fermenting plant

material, yeast and sugars.

C1.5.1 Obtaining useful substances from crude oil

Hydrocarbons can be cracked to produce smaller more useful molecules. The process

involves heating the hydrocarbons to vaporize them. The vapors are passed over a hot

catalyst and heated to a very high temperature so that THERMAL DECOMPOSITION can

occur.

The produce of cracking includes alkane, and unsaturated hydrocarbons alkenes.

Alkanes NO DOUBLE BOND CnHn+2

Methane CH4

Ethane C2H6

Alkenes ONE DOUBLE BOND CnH2n

Ethene C2H4

Propene C3H6

- ALKENES are keen and therefore react with bromine water turning it from orange to

colourless.

- Some of the products of cracking are used as fuels for example methane.

C1.5.2 Polymers.


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Alkenes can be used to make polymers such as poly(ethane) and poly(propene) in these

reactions many small monomers join together to form long polymer chains.

Think of

polymers as plastics..

Polymers have many useful applications and new ones are being developed for example

packing materials, hydrogels & wound dressings (an exam question would most likely askyou to name two examples and possibly explain them)

The majority of polymers are not biodegradable, microbes do not break them down, this

leads to issues in waste disposal most polymers end up in landfill.

Carrier bags are starting to be made from polymers and cornstarch, these break down more

easily.

C1.5.3 Ethanol

Ethanol can be made by hydrating ethene with steam in the presence of a catalyst.

It can also be produced by the fermentation of yeast using renewable plant material.

Sugar -> CO2 + ethanol

C1.6 Plant oils and their uses

Many plants produce useful oils that can be converted into consumer prodocust inckuded

processed foods. Emulsions can be made and have a number of sues. Vegetable oils can be

hardened to make margarine. Biodiesel fuel can be produced from vegetable oil. Vegetable

oil contains a high level of energy, too much of this can negatively impact on ones health.

C1.6.1 Vegetable oils

Some fruits, seeds and nuts are rich in oils that can be extracted. The plant material is

crushed and the oil is remove by pressing or in some cases by distillation.


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Vegetable oils are important foods and fuels as they provide a lot of energy. They also

provide nutrients.

Vegetable oils have higher boiling points than water, this means foods can be cooked at a

higher temperature and therefore more quickly it also produces different flavors and

increases the energy content of the food.

C1.6.2 Emulsions

Oil do not dissolve in water. They can be used to produce emulsions. Emulsions are thicker

than oil or water and have many uses that depend on their properties. They provide better

texture, coating ability and appearance for example ice cream and cosmetics and paints.

Emulsifiers have both hydrophilic and hydrophobic properties this bonds together the oilthat is dispersed in the water and prevents them from separating.

1.6.3 Saturated and unsaturated oils

Vegetable oils that are unsaturated contain double c=c bonds. These can be detected by

reacting with bromine water, they turn it colorless. Vegetable oils that are unsecured can behardened by reacting them with hydrogen in the presence of nickel catalyst at 90 degrees.

Hydrogen adds to the c=c bonds. These hydrogenated oils have higher melting points so

they are solids at room temperature, these are useful in cakes and pastries.

C1.7 Changes in the earths structure

The earth and atmosphere provide everything we need. The earth has a layered structure.

The surface if the earth and its atmosphere have changed since the earth was formed and

are still changing. The atmosphere has been much the same for the last 200 million years

and provides condition needed for life on earth. Recently human activities have resulted in a

rise of CO2 in the atmosphere.

Wegeners theory was not accepted for many years as at the time of proposal there was no

technology that could prove that the continents were moving.

Scientists cant predict earthquakes or volcano eruptions because they are very complex

phenomena and depend on the interactions of the motions of geological plates, the

pressure of magma in different places far underground etc. All of this is buried so deep in


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the earth that we can't measure it with sufficient resolution to tell what is really happening,

let alone what will happen in the future.

Co2 released by burning fossil fuels and other human activities is causing more to be

released into the atmosphere, this is a potential cause of more extreme weather and

climate change.

We do not know how life was first formed due to a lack of evidence, there are many

theories that are viable for example development of multicellular organisms from amino

acids there is evidence of this from fossil records and DNA sequences, there are also other

beliefs by people that a god or higher being created the earth, although there is no

evidence to prove it, and a large amount of evidence to disprove it (for example darwins

theory of evolution)..

C1.7.1 The earths Crust

The earth consists of a core, mantle and crust this is surrounded by the atmosphere.

The earths crust and upper mantle are cracked into a number of tectonic plates. Convection

current within the earths mantle driven by heat released from radioactive processes cause

the plates to move at relative speeds of a few centimetres per year.

The movement scan be sudden, and potentially disastrous examples of this are earthquakes

and volcanic eruptions.

C1.7.2 The earths atmosphere

For 200 million years the atmosphere has been largely the same. Around 80% nitrogen and

around 20% oxygen with small proportions of other gasses such as CO2, water vapour and

noble gasses.

During the first billion years if earths existence, there was intense volcanic activity, this

released the gases that formed into the early atmosphere and water vapour that condensed

to form the oceans. There are several theories about how the atmosphere was formed, one

theory is that the atmosphere was mainly CO2, there may also have been ammonia and

methane in small amounts. There are many theories as to how life was formed. One theory

is that life was formed due to interactions between ammonia, lightning and hydrocarbons.


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Most of the carbon from co2 in the air is currently locked in sedimentary rock and fossil

fuels, the oceans also act as a reservoir for co2, but too much has an adverse affect on

marine life. The release of co2 by burning fossils fuels increases the level of co2 in the

atmosphere. Air is a mixture of different gasses with different boiling points and can be

fractionally distilled to provide a source of raw materials used in industrial processes.

P1.4.1 Generating electricity

Some power stations use heated water to turn a turbine these include; fossil fuels, nuclear

and combustible biofuels. Water and wind can be used to directly turn turbines. Electricity

can also be produced from the power of the sun. In volcanic areas hot water and steam rise

to the surface the steam can be tapped and used to drive turbines, this is geothermal

energy. Small scale production of electricity is useful for some areas and uses for example

solar cells for road signs.

P1.4.2 The national Grid

Electricity is distributed via the national grid from power stations to homes. Transformers

are an essential part in the national grid. They increase voltage and reduce current to

transfer power to reduce loss, then reduce voltage and increase current to make the power

safe for use in homes.

P1.5 The use of waves for communication and to provide evidence the universe isexpanding

Electromagnetic radiations travel as waves and move energy from one place to another.

They can all travel through a vacuum and do so at the same speed. The waves cover a

continuous range of lengths called the electromagnetic spectrum. Sound waves and some

mechanical waves are longitudinal and cannot travel through a vacuum. Non sound waves

are transverse.

P1.5.1 General properties of waves.

Waves transfer energy, and they can be transverse or longitudinal. In a transverse wave the

oscillations occur perpendicular to the direction of energy transfer, in a longitudinal wave

the oscillations are parallel to the direction of energy transfer. Sound and mechanical waves

require a medium Electromagnetic waves are transverse, sound waves are longitudinal and

mechanical waves can be either. All electromagnetic waves travel at the same speed

through a vacuum. Longitudinal waves show areas of compressions and rarefraction. Waves

can be reflected, refracted or diffracted. Waves undergo a change of directions when they

are refracted at an interface.


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Significant diffraction only occurs when the wavelength is the same size as the gap.

All waves obey the equation: v=f*a

V= speed m/s f= frequency in hertz A= wavelength in metres.

Wave communication

Radio waves can be used for television and redio.

Microwaves can be used for phones and sattalite tv.

Infrared can be used for remtoes.

Visibile light can be used for photography

P1.5.3- Sound

Frequency = pitchAmplitude = Volume

P1.5.4 Red shift

- If a wave source is moving relative to an observe there will be a change in observedwavelength

- Further away galaxies are moving away faster- The faster something is moving away the longer the observed wavelength will be, soin visible light it will appear red- Things moving quickly toward us have the opposite effect, the light shifts theopposite way and appears more blue.

- Red-shift provides evidence that the universe originated from one singularity- CMBR is a form of electromagnetic radiation filling the universe it comes fromradiation present shortly after the beginning of the universe

- The big bang theory is the only one that can explain CMBR


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BIOLOGY

Adaptations:

Competition:

Plants compete for light water space and nutrients.

Animals compete for food, territory and mates.Competition is key for survival and therefore reproduction. This is important as it means

continuation of the species.

Extremophiles:

High or low levels of salt, heat and pressure.

Bacteria are usually highly affected by high levels of salt but some bacteria are tolerant to

salt. Some types of trees are adapted to salt water

Most living things require are 37 degrees C. Camels can tolerate 40+ degrees less

competition for resources in this environment

Bacteria 80 degrees hot springs

Enzymes work best at 37 degrees USUALLY

Pressure - bottom of the ocean bacteria have adapted to this, some fish too as well as some

sea mammals such as whales

Adaptations:

Surviving in cold environments for example thick fur, layers of fat this reduces heat loss

traps air good insulator. White camouflage to allow it to not be seen very easily. Small ears

which reduce heat loss as they have a smaller surface area

Elephants want to rid of heat large surface area allows for easier heat loss (large ears)


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Cacti can survive in dry conditions as it has a thick stem to store water. The leaves have a

low surface area to allow less water loss. A large number of roots.

Factors Affecting the Distribution of Living Things

Things that affect the population size of living things in a particular area.

Non living and living factors.

Non living: temperature, nutrients, rainfall, pollution

Living: Competition, Predators, Disease.

Pollution indicators:

Many varieties of Lichens cannot grow when the air is polluted, it is sensitive to sulphur

dioxide.

Invertebrates are bio indicators for water pollution

Fresh water shrimp will grow in no pollution, blood worm will grow in polluted water.

Decay:

Living things remove materials from the environment. Plants require nutrients for healthy

growth for example mineral ions. Mg for chlorophyll.

Animals require nutrients for growth, movement ect by eating plants or other animals.

Every living thing will die eventually inside their body are all these nutrients it is

important these nutrients are returned to the environment.

The process of this is called decay.

Microorganisms play a key role in decay.

It is important that animals have nutrients from decay.Compost is plant material that contains nutrients that are broken down by microbes the

best condition is with plenty of oxygen, a warm temperature and moisture.

Decay is important for plant growth as in ensures plants can get the nutrients they need

from the soil

Variation in Living things

Characteristics are basically features for example height of colour and how the living thing

looks.

Features in all living things are controlled in the same way.

In sexual reproduction the parents pass on some of their Characteristics to their offspring,

this also sometimes happens in plants.

Genes are found in the chromosomes which are inside the nucleus of any cell of a living

thing. Chromosomes are made up of DNA this is the same in both plants and animals.

Genes control characteristics (features)

Genes control some features, others are controlled by the environment some are

controlled by both.

Sexual Vs asexual reproduction:

Sexual reproduction


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Sexual requires two parents, a male and a female gamete (sperm and eggs in humans)

(Pollen and egg cells)

Fusion of the gametes must occur, the gametes both carry genetic information in the form

of genes.

Variation, some features of both parents

Offspring from sexual reproduction will not be identical to the parents

Asexual reproduction

there is no mixture of genetic material, the offspring is identical (a clone) of the parent.

Some plants (strawberry, spider plant), some bacteria and simper living beings.

Cutting can be taken from a plant and then planted into soil to quickly and cheaply produce

a genetically identical plant to the parent plant. When rooting powder is used.

Tissue Culture, Embryo Transplants and Adult Cell Fusion

Tissue culture small group of cells are taken from the root, they are then encouraged togrow using agar jelly this provides vitamins sugar and hormones for growth it is important

an aseptic technique is used. The roots and shoots that grow in the agar are then planted,

the advantage of this is you get 1000s of clones of the original plant.

Embryo Transplants an egg cell is fertilised hen allowed to grow into an embryo a ball of

unspecialised cells, this mean these cells havemt started becoming individual cells of the

animal. At this point the embryo is split into more smaller cells which are used to produce

individuals, this produces identical animals when the cells are implanted into host mothers

Adult cell fusuion an egg is extracted and the nucleus is removed, a skin cell is removedfrom the animal that is being cloned and the nucleus is removed and implanted into the egg,

the egg is then given a small electric shock to start its growth, th is egg is then implanted

into a host mother.

Gene transfer and GM crops

Genetic engineering is the transfer of genes from one living thing to another.

GM products are those that have genes from another living thing.

A cell from the plant can be removed during the early development, then an insect repelling

gene (produces a protein which kills insects) in placed into the chromosome of the plant

cell. As the plant reproduces this gene is duplicated.

Genetically modified crops (GM) can effect ecosystems and it could have an effect on the

people that eat them, could the genes spread to other living things, could it cause unwanted

adaptations in animals.

Evolution:

Darwin suggested that in every species there is always some level of variation between

species. So therefore there is always a weaker sub species. For example a shorter giraffe will

not be able to get high up food and therefore will die, the taller giraffes will be more likely

to live longer and reproduce to pass on the taller neck genes therefore survival of the fittest.


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Lamarck suggested that because giraffes were stretching all day every day that their necks

became longer throughout their life and this feature is passed on.

Genetic features cannot be changed over a lifetime, environmental factors are not passed

on.

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