Part C - The Impact of Science
C.1 Energy and physical resources
C.1.1 Electrical energy
Essential Idea:
Models of electrical energy have developed with time as our understanding of the science has developed. With this man has created a multitude of devices to harness the power and flexibility of electricity.
Understanding the Nature of Science:
A brief qualitative overview of the historical development of electricity through individual scientists should be undertaken specifically with regard to the NOS links.
Early forms of electricity studied included lightning and static electricity.
Hauksbee strived to understand the natural phenomena by asking questions and looking for explanations, this is thematic investigation.
Franklin was crucial in identifying effects and proposing causes.
Luigi Galvani considered electricity to be a property of living things.
Alessandro Volta disproved Galvani’s ideas by producing a continuous flow of electricity from a battery which was made from different metals.
Hans Christian Ørsted and Andre-Marie Ampere were the first to investigate the connection between electricity and magnetism. This resulted in the invention of the electric generator and the electric motor by Michael Faraday.
By employing quantitative thinking, Volta established the concept of electrical current i.e. the amount of electricity flowing out of a source.
Quantitative observations allowed a more mathematical approach and formulation of laws by Coulomb, Faraday and Ohm among many others.
Guidance:
Electrical current involves the movement of charged particles in an electric or magnetic field. This flow of charge can do work on other systems.
Scientists describe electrical phenomena in terms of: Electric charge; Electric current; Potential difference/voltage.
This is a hybrid description of energy where the work done is calculated but is described per unit of charge that has flowed.
C.1.2 Using electrical energy I - portable electricity
Essential Idea:
Improvements in the understanding of science have enabled the development of a range of devices, to enhance the quality of life, that are independent of fixed sources of energy.
Understanding the Nature of Science:
Both batteries and fuel cells convert chemical energy into electrical energy.
Primary cells are batteries that employ non-reversible chemical reactions and therefore cannot be recharged.
The variation of the voltage produced in relation to the reactivity of the metals used in an electrochemical cell illustrates the recognition of patterns in science.
Secondary cells are batteries that employ reversible chemical reactions that allow them to be recharged.
Fuel cells use chemical reactions that continuously consume a fuel to produce electricity.
Guidance:
Relate the activity series to the voltage which can be produced in an electrochemical cell. The series will be limited to Mg, Zn, Fe, Sn, Ag.
Details of the chemical reactions occurring will not be expected.
C.1.3 Using electrical energy II – centralized electrical production
Essential Idea:
The production of electricity through the movement of electrical coils in magnetic fields is most efficient when it takes place in large centralised facilities linked to a distribution network. The increasing global demand for electricity was met by using cheap fossil fuels that emit carbon dioxide, causing the enhanced greenhouse effect. I.e man made global warming.
Understanding the Nature of Science:
The movement of a conductor through a magnetic field produces an electric current. This discovery by Faraday lead to a greater understanding of fields and an application of a more mathematical language.
Electricity is a secondary energy source as it is generated by non-renewable and renewable primary sources of energy.
In a power station, the primary energy source drives a turbine (either directly – wind, or indirectly – steam from the combustion of fuels) which rotates the generator coils to produce a current.
Coal powered steam engines were the initial sources of energy for generators but more recently there has been a shift to oil, gas and nuclear power.
The use of computer modelling has allowed for the development of even more efficient power generation using a wider variety of primary energy sources to cater for differing locations and access to natural resources.
Electric current can be direct (DC) in which electrons move in one direction or alternating (AC) current the electrons oscillate rapidly back and forth. A generator can be designed to produce either AC or DC.
AC has been used for large scale distribution for domestic and industrial use owing to the need for high voltages for efficient distribution.
Energy is distributed at high voltage through a supply network and the voltage reduced by transformers before delivery to the end user.
Guidance:
A detailed knowledge of the generator is not required but any understanding should relate to A.1.1 Fields.
C.1.4 Renewable and non-renewable energy
Essential Idea:
Our increasing dependence on reliable and affordable energy supplies is a challenge for developed and developing countries alike. Industrialization, economic growth and increasing population are stressing the finite energy resources of Earth. As a result of environmental issues caused by burning fossil fuels scientists have needed to consider how we can most effectively harness natural sources of energy for the good of all. Our quest should be for a sustainable pattern of energy consumption.
Understanding the Nature of Science:
Some carbon based materials found in the Earth’s crust, known collectively as fossil fuels, are a potent, though finite, source of energy.
Recent research in renewable energy sources has been brought about due to increased industrialisation and increased population yet some countries support the use of fossil fuels for their energy needs.
The basic operating principles of a variety of energy sources (renewable and non-renewable) and their relative efficiency. The focus should be on the relative advantages and disadvantages of each.
The choice of primary energy source depends on availability of resources, capital costs and running costs, as well as potential environmental impact.
The development of more efficient turbines depends on the increased power of instrumentation and computer simulations.
Guidance:
Only a brief overview of the mechanisms for each energy source is required.
Non-renewable sources to be considered are fossil fuels (oil, natural gas, coal) and nuclear fission.
Renewable sources to be considered are wave, hydroelectric power, tidal, wind, solar (thermal and photovoltaic), geothermal, biomass.
C.1.5 Nuclear Power
Essential Idea:
The most surprising energy change of all: mass to (nuclear) energy and the consideration of mass as a form of energy. This is an excellent indication of how unanticipated discoveries can totally transform particular fields of human endeavour.
Understanding the Nature of Science:
The aim here is not to give an exhaustive account of the physics of nuclear energy production but rather to emphasize the paradigm shift that Einstein instigated.
Nuclear power is commonplace throughout the world, generating a significant proportion of the total energy output of many countries.
Nuclear fission is the process where the nucleus of an atom splits into several smaller fragments. The final total mass is less than the initial mass; the difference in mass (mass deficit) appears as energy.
Controlled fission is used for nuclear power and uncontrolled fission for nuclear weapons. The converted mass appears as kinetic energies of the fragments and as excited energy states of the products.
Sustained nuclear fission provides the nuclear power used to generate electrical energy by means of conventional steam turbines and generators.
The ability to do work in nuclear reactions is much greater than from the burning of fossil fuels because of the extremely high energy density of uranium-235.
The development and effective, safe control of nuclear reactors depends on the advances in technology and the power of instrumentation.
Although accidents at nuclear power stations are rare but when they occur they can be catastrophic. Risk assessments are required.
Natural uranium requires enriching in one particular isotope, uranium-235, to be used as a reactor fuel and even greater enrichment for weapons use.
Uranium is only mined in a few countries and its trade has obvious ethical and political implications.
Guidance:
Details of the nuclear reactions involved in a nuclear power plant are not required.
C.1.6 Forces and physical properties
Essential Idea:
One of the strengths of scientific thinking is that a limited number of fundamental concepts can be used to explain a wide range of phenomena. In this reductionist approach four fundamental forces (strong nuclear, weak nuclear, electromagnetic and gravitational) can be used to explain the way in which fundamental particles interact to produce the amazing variety of properties that we observe in the matter that comprises the universe.
Understanding the Nature of Science:
Experimental evidence shows the properties of materials depend on the particles present and the forces between them. In general metallic, ionic and covalent bonds are strong, whereas forces between molecules are much weaker. A consequence is that almost all liquids and gases have molecular structures.
Ionic and covalent bonds depend on the relative position of the particles, giving rise to brittle structures, whereas others, such as metallic bonding and most intermolecular forces, are much less dependent on their positions and hence produce malleable materials.
Guidance:
The topic focuses on the links between material properties and chemical structure and the uses made by humans of these material properties. It does not explore sub-atomic structures.
C.1.7 Uses of physical resources
Essential Idea:
The key challenge is how to maintain environmental quality for future generations while at the same time providing for the needs of current generations.
Understanding the Nature of Science:
1 An understanding of scientific processes is the basis for the development and use of basic raw materials and the invention and production of new materials. Population growth and economic growth results in a high demand for large quantities of raw materials (steel, industrial wood, fuel wood, cement) and materials such as Aluminium and plastics. Some very rare important materials are required for some high technology products such as computers.
2 The concept of World Reserves Index.
3 Every material/product has an energy cost in its exploration, extraction production, use, reuse and disposal. Calculating the energy cost requires a knowledge of scientific processes and is the work of scientists. The carbon footprint is an important consideration.
4 Production of every material and every product has environmental impacts including recycling. Use of Life Cycle Analysis (LCA) is the only way to determine environmental impacts with any certainty. It can only be conducted on a scientific basis by trained scientists.
C.2 Transport
C.2.1 Unbalanced forces
Essential Idea:
Among other things, the history of human progress can be marked by an increasing ability to create and control forces through technology, in particular the forces needed for translational motion.
Understanding the Nature of Science:
All motion is the result of external unbalanced forces acting on a body.
The science of motion is characterised by a common terminology that includes displacement, speed, velocity, and acceleration.
Guidance:
Simple calculations for resultant forces are only required for linear situations.
C.2.2 Transportation Systems
Essential Idea:
Science and technology have produced mass transportation of people and goods around the globe that has changed our way of life. However, this mass movement has a major impact on the environment and is not sustainable.
Understanding the Nature of Science:
An understanding of energy transfer, in combination with advances in materials technology and fuel extraction and refinement, have allowed humans to create engines able to generate very large forces that can be used to power transportation.
Oil-based fuels are used in the internal combustion engine. A controlled explosion is used to drive a piston up and down in a cylinder.
Jet engines are subject to very large tensile forces and special materials have been developed to cope with these.
Electric cars use stored electric energy to produce motion. Some modern cars have a hybrid petrol-electric engine: Both these technologies require a battery of cells to be carried in the vehicle.
Hydrogen-cell transport: Hydrogen gas is used in a fuel cell to produce electric current with water as its waste product.
Engines use a variety of fuels, and the means of extracting the energy from the fuels produces waste products. Some waste products are damaging to the environment.
Guidance:
Students will require sufficient prior knowledge to enable them to understand the underlying concepts of the electric motor (e.g. a flow of charge is known as an electric current, in a conductor the charge carrier is an electron, simple direction rules for the direction of magnetic force).
Only the dc electric motor is required.
The choice of engines is related to their environmental impact.
C.3 Communications
C.3.1 Introduction to communications
Essential Idea:
Modern developments in science have allowed continuous communication and information exchange at large volumes and high speeds, over long distances. This has transformed our everyday lives.
Understanding the Nature of Science:
The historical development of communications was dependent on the technology.
A revolution in communications was brought about by the ability to interconvert audio signals and electrical signals using a microphone and reverse this at the opposite end using a loudspeaker.
Oscillations of current in an electrical conductor emit electromagnetic waves that mirror the oscillations. These waves may be detected by a conductor at some distance from the source, without there being any physical connection between the two.
Broadcasting techniques using electromagnetic waves allow a signal to be received at many stations. This has brought nations into closer contact and helped to overcome cultural differences.
The application of the principle of electromagnetic induction to the transmission of audio signals is a wonderful example of the creative, imaginative way that scientists have adapted basic discoveries to make possible things that had previously been considered impossible.
C.3.2 Electromagnetic induction and electromagnetic waves
Essential Idea:
The unifying concept of electromagnetic waves and the imagination to use them for transmitting information in many forms together form the basis for developments in global communications.
Understanding the Nature of Science:
Electromagnetic induction: The motion of an electrical conductor in a magnetic field generates a current in the conductor. If this motion is linked to the vibrations caused by sound waves, the electrical current will oscillate in a similar manner and this can be transmitted along a conductor. At the other end of the conductor, the changes in the electrical current can cause the movement of the conductor, which can be converted back to sound waves that, ideally, are identical to the original ones.
Electromagnetic waves: Electromagnetic waves are of frequencies well above audio frequencies so the audio signal has to be superimposed on the wave. This can be done by amplitude modulation or frequency modulation.
C.3.3 Digital signals
Essential Idea:
The binary counting system using only 0’s and 1’s is the basis of all modern electronic communication.
Understanding the Nature of Science:
The electronic circuits involved operate according to Boolean logic using electronic gates.
The use of digital conversion has only become possible in recent decades because of the increased speed of computers carrying out analogue to digital conversion.
Noise from many sources can affect the quality of an analogue signal, but digital transmission has no loss of quality.
A wave may be converted to a digital signal by successively sampling the amplitude of the wave and the process reversed to recreate the wave.
C.3.4 Optical fibres
Essential Idea:
The technology of optical fibres and the simple physics involved in transmitting light along them has led to a global system of information transfer and communication.
Understanding the Nature of Science:
Total internal reflection allows light signals to be transmitted down glass fibres as an alternative to electrons moving in conductors.
The introduction of optical fibres has been totally dependent on the ability of manufacturers to produce very thin fibres of highly transparent glass.
Optical fibres are highly transparent, but regular amplification of the signal is still required.
Many signals can be transmitted simultaneously in an optical fibre using light without interference resulting in a high bandwidth.
C.3.5 Communication networks
Essential Idea:
The imaginative leap to use orbiting satellites for the transfer of information has allowed for global communications on a large scale. More recent developments in computing power and cell phone networks have led to another revolution in communications.
Understanding the Nature of Science:
Broadcast coverage requires the siting of transmitters that will deliver appropriate signal strength to the desired audience.
Microwave frequency signals can be transmitted through the atmosphere to geostationary or polar orbiting satellites, which re-transmit the signal back to Earth.
Transmission of signals from satellites is particularly efficient because of the wide area they cover and reduced interference from geographical features because of the high angle of incidence. Person to person communications, in addition, require routing from the sender to a particular recipient.
Telephone conversations, whether mobile or landline, require directing from a particular caller to a specific recipient.
C.4 Food Security
C.4.1 Nutritional requirements
Essential Idea:
Epidemiology and scientific experiments have established a causal relationship between diet and health.
Understanding the Nature of Science:
Nutrients are the chemicals found in food that are essential for life.
Malnutrition can result from insufficient or excess intake of any of nutrients; this varies significantly between populations.
There is a debate about the best way to assess a healthy body.
Reliable nutrition information can only be obtained from verifiable scientific evidence.
Methods of preservation and cooking may affect the nutritional content of food and cause adverse effects on health.
Food additives extend the shelf life of food products, and improve the appearance or nutritional content.
Guidance:
Causes of malnutrition include: protein deficiency, vitamin and mineral deficiencies, obesity, anorexia, geographical location, economic status and lack of education.
Methods of preservation include drying, salting, freezing, smoking, pickling, fermentation and synthetic preservatives.
C.4.2 Agricultural science
Essential Idea:
Agriculture has improved food yields through the domestication of animals and plant cultivation, contributing to the quality of modern life and an increase in life expectancy but at some detriment to the environment.
Understanding the Nature of Science:
There are many challenges in providing sufficient food to a growing global population.
Scientific innovation in agrochemicals and in land use has led to increased food yield that has helped to support the growing population.
A rise in monocultures has led to an increased vulnerability to disease and pests, promoting the use of pesticides and selective herbicides.
Animals are frequently treated with antibiotics and hormones to increase food yields and profitability.
The use of agrochemicals has a negative impact on the environment.
The term organic, when used to describe foods that have been grown without agrochemicals is not a scientific term.
Food Miles describes the impact that changing patterns of food production has had on the seasonal availability of food. There needs to be a balance between growing crops in the optimum climate and transportation to markets.
Pressures on food distribution are increasing.
Guidance:
The difference between past and current practices of biotechnology should be discussed.
Pressures on food distribution may include changing global weather patterns, political instability, unreliable food supply patterns, consumer demand and economic gain.
The difficulties in providing sufficient food could include availability of arable land, accessible water, population pressures, climate change, economic factors, transport and storage.
Agrochemicals include fertilizers, herbicides, pesticides and fungicides.
Biological controls should also be considered.
C.4.3 Biotechnology
Essential Idea:
Genetic modification has both positive and negative implications including ethical dimensions. Scientific literacy and the public understanding of science is vital for decision making on the use of biotechnology.
Understanding the Nature of Science:
The development of genetically modified (GM) organisms and foods increase the rate and enhance the capability of, changes resulting from selective breeding.
The safety of GM foods is still under debate and this has implications for public acceptance and regulation.
Differences in regional GMO regulations in combination with the globalisation of trade leading to the increased import and export of food makes informed decision-making difficult.
C.5 Medicine
C.5.1 Science and Health
Essential Idea:
Evidence based medicine has resulted in major improvements in health, quality of life, increased life expectancy and population growth.
Understanding the Nature of Science:
Progress in the diagnosis and treatment of many diseases and disorders has been advanced by scientific research.
Increased life expectancy in some countries will have negative consequences on resources and medical care.
Epidemiologists study the incidence, distribution and control of diseases.
Causal relationships have been established between some pathogens and infectious diseases.
Some health practices are not evidence based.
Funding is required for continued research into infectious diseases, especially in the area of prevention.
New diseases are appearing due to pathogens crossing species barriers.
There is a correlation between poverty and the incidence of infectious diseases.
Public health policies promoting disease prevention have been developed by the scientific community and government agencies.
Vaccinations can prevent and eliminate some diseases. In some countries, public understanding has been influenced by non-scientific opinion.
Guidance:
Communicable diseases could include HIV/AIDS, malaria, cholera, tuberculosis, influenza (e.g. H5N1) and Ebola.
Public health policies could include reduction in infant mortality, vaccination programmes and how to deal with an ageing population.
Medical practices subject to discussion could include reflexology, homeopathy, magnetism, colonic hydrotherapy, acupuncture and chiropractic treatments.
C.5.2 Modern medicine
Essential Idea:
Advances in technology and collaboration between the scientific community, pharmaceutical industry and governments has been instrumental in improving the diagnosis and treatment of many of the diseases and disorders that threaten health.
Understanding the Nature of Science:
Pharmaceutical drugs have been synthesized and derived from natural sources.
Increasing resistance to current drug treatments is a threat to public health.
Drug treatments can be preventative or curative.
Contraceptive drugs can be used as a means of controlling the birth rate.
The effectiveness of a drug is closely related to the chemical groups present and the three dimensional shape of the molecule.
Computer software is used to design molecules as potential drugs.
Experimentation and clinical studies are needed to demonstrate the effectiveness, safety, and limitations of new drugs.
Advances in biomedical diagnostic tests and technology have enabled quick and accurate analysis of medical conditions.
DNA profiling/sequencing has advanced medical diagnosis and treatment.
With health care costs, including expensive diagnostic equipment, there needs to be a balance between benefit and cost.
Some medical practices are subject to debate, including experimental cancer drugs and the use of performance enhancers in sports.
Guidance:
Pathogens that can be treated by drugs could include bacteria, worms, prions and viruses.
Preventative pharmaceutical drugs could include contraceptives and statins.
Medical disorders treated by modern pharmaceutical drugs could include depression, diabetes, coronary heart disease, high blood pressure and Parkinson’s disease.
Drug experiments could include sampling, cohort studies, case control studies, double-blind tests and clinical trials.
DNA profiling/sequencing is able to classify certain types of cancer and indicate risk factors for certain diseases.
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