Subject content

3.1 Introduction to Subject Content

Introduction

The subject content of this specification is presented in five sections:

  • How Science Works
  • the three sections of substantive content, Further Additional Science –Biology 3, Further Additional   Science – Chemistry 3, Further Additional Science – Physics 3 (Units 1, 2 and 3)
  • and the Controlled Assessment (Unit 4).

It is intended that the How Science Works content is integrated and delivered not only through the Controlled Assessment but also through the context of the content of Further Additional Science – Biology 3, Further Additional Science – Chemistry 3, and Further Additional Science – Physics 3.

The organisation of each sub-section of the substantive content is designed to facilitate this approach. Each of the sub-sections of Further Additional Science – Biology 3, Further Additional Science – Chemistry 3, and Further Additional Science – Physics 3 starts with the statement:

'Candidates should use their skills, knowledge and understanding to:'.

This introduces a number of activities, for example:

  • evaluate the conditions necessary in an industrial process to
    maximise yield and minimise environmental impact.

These activities are intended to enable candidates to develop the skills, knowledge and understanding of How Science Works.

Other aspects of the skills, knowledge and understanding of How Science Works will be better developed through investigative work and it is expected that teachers will adopt a 'practical enquiry' approach to the teaching of many topics.

The subject content is presented in two columns. The left-hand column lists the content that needs to be delivered. The right-hand column contains guidance and expansion of the content to aid teachers in delivering it and gives further details on what will be examined.

At the end of each section there is a list of ideas for investigative practical work
that could be used to help candidates develop their practical enquiry skills to understand and engage with the content.

Opportunities to carry out practical work should be provided in the context of each section. These opportunities should allow candidates to:

  • use their knowledge and understanding to pose scientific questions and
    define scientific problems
  • plan and carry out investigative activities, including appropriate risk
    management, in a range of contexts
  • collect, select, process, analyse and interpret both primary and secondary
    data to provide evidence
  • evaluate their methodology, evidence and data.

In the written papers, questions will be set that examine How Science Works in biology, chemistry and physics contexts.

Examination questions will use examples that are both familiar and unfamiliar to candidates. All applications will use the knowledge and understanding developed through the substantive content.

Tiering of subject content

In this specification there is additional content for Higher Tier candidates. This is denoted in the subject content in bold type and annotated as HT only in Sections 3.3 to 3.5.

3.2 How Science Works

How Science Works

This section is the content underpinning the science that candidates need to know and understand. Candidates will be tested on How Science Works in both written papers and the Controlled Assessment.

The scientific terms used in this section are clearly defined by the ASE in The Language of Measurement: Terminology used in school science investigations (Association for Science Education, 2010). Teachers should ensure that they, and their candidates, are familiar with these terms. Definitions of the terms will not be required in assessments, but candidates will be expected to use them correctly.

The thinking behind the doing

The thinking behind the doing

Science attempts to explain the world in which we live. It provides technologies that have had a great impact on our society and the environment. Scientists try to explain phenomena and solve problems using evidence. The data to be used as evidence must be repeatable, reproducible and valid, as only then can appropriate conclusions be made.

A scientifically literate person should, amongst other things, be equipped to question, and engage in debate on, the evidence used in decision-making.

The repeatability and the reproducibility of evidence refers to how much we trust the data. The validity of evidence depends on these, as well as on whether the research answers the question. If the data is not repeatable or reproducible the research cannot be valid.

To ensure repeatability, reproducibility and validity of evidence, scientists consider a range of ideas that relate to:

  • how we observe the world
  • designing investigations so that patterns and relationships between variables may be identified
  • making measurements by selecting and using instruments effectively 
  • presenting and representing data
  • identifying patterns and relationships and making suitable conclusions.

These ideas inform decisions and are central to science education. They constitute the 'thinking behind the doing' that is a necessary complement to the subject content of biology, chemistry and physics.

Fundamental ideas

Fundamental ideas

Evidence must be approached with a critical eye. It is necessary to look closely at how measurements have been made and what links have been established. Scientific evidence provides a powerful means of forming opinions. These ideas pervade all of How Science Works.

  • It is necessary to distinguish between opinion based on valid, repeatable and reproducible evidence and opinion based on non-scientific ideas (prejudices, whim or hearsay).
  • Scientific investigations often seek to identify links between two or more variables. These links may be:
    • causal, in that a change in one variable causes a change in another
    • due to association, in that changes in one variable and a second variable are linked by a third variable
    • due to chance occurrence.
  • Evidence must be looked at carefully to make sure that it is:
    • repeatable
    • reproducible
    • valid.

Observation as a stimulus to investigation

Observation as a stimulus to investigation

Observation is the link between the real world and scientific ideas. When we observe objects, organisms or events we do so using existing knowledge. Observations may suggest hypotheses that can be tested.

  • A hypothesis is a proposal intended to explain certain facts or observations.
  • A prediction is a statement about the way something will happen in the future.
  • Observations can lead to the start of an investigation, experiment or survey. Existing models can be used creatively to suggest explanations for observations (hypotheses). Careful observation is necessary before deciding which variables are the most important. Hypotheses can then be used to make predictions that can be tested.
  • Data from testing a prediction can support or refute the hypothesis or lead to a new hypothesis.
  • If the hypotheses and models we have available to us do not completely match our data or observations, we need to check the validity of our observations or data, or amend the models.

Designing an investigation

Designing an investigation

An investigation is an attempt to determine whether or not there is a relationship between variables. It is therefore necessary to identify and understand the variables in an investigation. The design of an investigation should be scrutinised when evaluating the validity of the evidence it has produced.

  • An independent variable is one that is changed or selected by the investigator. The dependent variable is measured for each change in the independent variable.
  • For a measurement to be valid it must measure only the appropriate variable.
  • A fair test is one in which only the independent variable affects the dependent variable, as all other variables are kept the same. These are called control variables.
  • When using large-scale survey results, it is necessary to select data from conditions that are similar.
  • Control groups are often used in biological and medical research to ensure that observed effects are due to changes in the independent variable alone.
  • Care is needed in selecting values of variables to be recorded in an investigation. A trial run will help identify appropriate values to be recorded, such as the number of repeated readings needed and their range and interval.
  • An accurate measurement is one that is close to the true value.
  • The design of an investigation must provide data with sufficient precision to form a valid conclusion.

Making measurements

Making measurements

When making measurements we must consider such issues as inherent variation due to variables that have not been controlled, human error and the characteristics of the instruments used. Evidence should be evaluated with the repeatability and validity of the measurements that have been made in mind.

  • There will always be some variation in the actual value of a variable, no matter how hard we try to repeat an event.
  • The resolution of an instrument refers to the smallest change in a value that can be detected. 
  • Even when an instrument is used correctly, human error may occur; this could produce random differences in repeated readings or a systematic shift from the true value.
  • Random error can result from inconsistent application of a technique. Systematic error can result from consistent misapplication of a technique.
  • Any anomalous values should be examined to try to identify the cause and, if a product of a poor measurement, ignored.

Presenting data

Presenting data

To explain the relationship between two or more variables, data may be presented in such a way as to make the patterns more evident. There is a link between the type of graph used and the type of variable represented. The choice of graphical representation depends upon the type of variable represented.

  • The range of the data refers to the maximum and minimum values.
  • The mean (or average) of the data refers to the sum of all the measurements divided by the number of measurements taken. 
  • Tables are an effective means of displaying data but are limited in how they portray the design of an investigation.
  • Bar charts can be used to display data in which one of the variables is categoric.
  • Line graphs can be used to display data in which both the independent and dependent variables are continuous.
  • Scattergrams can be used to show an association between two variables.

Using data to draw conclusions

Using data to draw conclusions

The patterns and relationships observed in data represent the behaviour of the variables in an investigation. However, it is necessary to look at patterns and relationships between variables with the limitations of the data in mind in order to draw conclusions.

  • Patterns in tables and graphs can be used to identify anomalous data that require further consideration.
  • A line of best fit can be used to illustrate the underlying relationship between variables.
  • Conclusions must be limited by, and not go beyond, the data available.

Evaluation

Evaluation

In evaluating a whole investigation the repeatability, reproducibility and validity of the data obtained must be considered.

Societal aspects of scientific evidence

Societal aspects of scientific evidence

A judgement or decision relating to social-scientific issues may not be based on evidence alone, as other societal factors may be relevant.

  • Evidence must be scrutinised for any potential bias of the experimenter, such as funding sources or allegiances.
  • Evidence can be accorded undue weight, or dismissed too lightly, simply because of its political significance. If the consequences of the evidence could provoke public or political disquiet, the evidence may be downplayed.
  • The status of the experimenter may influence the weight placed on evidence; for instance, academic or professional status, experience and authority.
  • Scientific knowledge gained through investigations can be the basis for technological developments.
  • Developments in science and technology have ethical, social, economic or environmental consequences, which should always be taken into account when evaluating the impacts of any new developments.
  • Advancements in science can have ethical implications. The effects of these must be taken into account in a balanced way to facilitate decision making.
  • Decisions are made by individuals and by society on issues relating to science and technology.

Limitations of scientific evidence

Limitations of scientific evidence

Science can help us in many ways but it cannot supply all the answers.

  • We are still finding out about things and developing our scientific knowledge.
  • There are some questions that we cannot answer, maybe because we do not have enough repeatable, reproducible and valid evidence.
  • There are some questions that science cannot answer directly. These tend to be questions where beliefs, opinions and ethics are important.

3.3 Unit 1: Further Additional Science- Biology 3

B3.1 Movement of molecules in and out of cells

We need to understand how biological and environmental systems operate when they are working well in order to be able to intervene when things go wrong. Modern development and technological research allow us to do so.

B3.1 Movement of molecules in and out of cells

The cells, tissues and organs in plants and animals are adapted to take up and get rid of dissolved substances. Different conditions can affect the rate of transfer. Sometimes energy is needed for transfer to take place.

Candidates should use their skills, knowledge and understanding to:

  • evaluate the development and use of artificial aids to breathing, including the use of artificial ventilators
  • evaluate the claims of manufacturers about sports drinks
  • analyse and evaluate the conditions that affect water loss in plants.

B3.1.1 Dissolved substances

a) Dissolved substances move by diffusion and by active transport.

b) Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.

Additional guidance:

Use of the terms turgor and plasmolysis is not required.

c) Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis.

d) Most soft drinks contain water, sugar and ions.

e) Sports drinks contain sugars to replace the sugar used in energy release during the activity. They also contain water and ions to replace the water and ions lost during sweating.

f) If water and ions are not replaced, the ion / water balance of the body is disturbed and the cells do not work as efficiently.

g) Substances are sometimes absorbed against a concentration gradient. This requires the use of energy from respiration. The process is called active transport. Active transport enables cells to absorb ions from very dilute solutions.

h) Many organ systems are specialised for exchanging materials. The effectiveness of an exchange surface is increased by:

  • having a large surface area
  • being thin, to provide a short diffusion path
  • (in animals) having an efficient blood supply
  • (in animals, for gaseous exchange) being ventilated.

i) Gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness.

j) The size and complexity of an organism increases the difficulty of exchanging materials.

k) In humans:

  • the surface area of the lungs is increased by the alveoli
  • the surface area of the small intestine is increased by villi.

 l) The villi provide a large surface area with an extensive network of capillaries to absorb the products of digestion by diffusion and active transport.

B3.1.2 Gaseous exchange     

a) The lungs are in the upper part of the body (thorax), protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm. 

Additional guidance:

Candidates should be able to recognise these structures on a diagram.

b) The breathing system takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air.

c) To make air move into the lungs the ribcage moves out and up and the diaphragm becomes flatter. These changes are reversed to make air move out of the lungs. The movement of air into and out of the lungs is known as ventilation.      

Additional guidance:

Candidates should be able to describe the mechanism by which ventilation takes place, including the relaxation and contraction of muscles leading to changes in pressure in the thorax.

B3.1.3 Exchange systems in plants

a) In plants:

  • carbon dioxide enters leaves by diffusion
  • most of the water and mineral ions are absorbed by roots.

b) The surface area of the roots is increased by root hairs and the surface area of leaves is increased by the flattened shape and internal air spaces.

c) Plants have stomata to obtain carbon dioxide from the atmosphere and to remove oxygen produced in respiration.

d) Plants mainly lose water vapour from their leaves. Most of the loss of water vapour takes place through the stomata.

  • Evaporation is more rapid in hot, dry and windy conditions.
  • If plants lose water faster than it is replaced by the roots, the stomata can close to prevent wilting.

e) The size of stomata is controlled by guard cells, which surround them.

Suggested ideas for practical work to develop skills and understanding include the following:

  • use sensors, eg spirometers, to measure air flow and lung volume
  • investigating potato slices in different concentrations of liquid in terms of mass gain and mass loss
  • design an investigation to measure the mass change of potato when placed in a series of molarities of sucrose solution
  • investigating the relationship between concentrations of sugar solution and change in length of potato strips
  • placing shelled eggs in different concentrations of liquid to observe the effect
  • placing slices of fresh beetroot in different concentrations of liquid to observe the effect, and then taking thin slices to observe the cells
  • observing guard cells and stomata using nail varnish
  • observing water loss from plants by placing in a plastic bag with cobalt chloride paper.

B3.2 Transport systems in plants and animals

Substances are transported around the body by the circulatory system (the heart, the blood vessels and the blood). They are transported from where they are taken into the body to the cells, or from the cells to where they are removed from the body. Modern developments in biomedical and technological research enable us to help when the circulatory system is not working well. Plants have separate transport systems for water and nutrients.

Candidates should use their skills, knowledge and understanding to:

  • evaluate data on the production and use of artificial blood products
  • evaluate the use of artificial hearts and heart valves
  • evaluate the use of stents.

B3.2.1 The blood system

a) The circulatory system transports substances around the body.

b) The heart is an organ and pumps blood around the body. Much of the wall of the heart is made from muscle tissue.

Additional guidance:

Knowledge of the cardiac cycle is not required.

c) There are four main chambers (left and right atria and ventricles) of the heart.

d) Blood enters the atria of the heart. The atria contract and force blood into the ventricles. The ventricles contract and force blood out of the heart. Valves in the heart ensure that blood flows in the correct direction. Blood flows from the heart to the organs through arteries and returns through veins. There are two separate circulation systems, one for the lungs and one for all other organs of the body.

Additional guidance:

Knowledge of the names of the heart valves is not required.

Knowledge of the names of the blood vessels associated with the heart is limited to aorta, vena cava, pulmonary artery and pulmonary vein.

e) Arteries have thick walls containing muscle and elastic fibres. Veins have thinner walls and often have valves to prevent back-flow of blood.

f) If arteries begin to narrow and restrict blood flow stents are used to keep them open.

Additional guidance:

Candidates should understand the importance of stents, particularly with reference to the coronary arteries.

g) In the organs, blood flows through very narrow, thin-walled blood vessels called capillaries. Substances needed by the cells in body tissues pass out of the blood, and substances produced by the cells pass into the blood, through the walls of the capillaries.

B3.2.2 The blood

a) Blood is a tissue and consists of a fluid called plasma in which red blood cells, white blood cells, and platelets are suspended.

b) Blood plasma transports:

  • carbon dioxide from the organs to the lungs
  • soluble products of digestion from the small intestine to other organs
  • urea from the liver to the kidneys.

c) Red blood cells transport oxygen from the lungs to the organs. Red blood cells have no nucleus. They are packed with a red pigment called haemoglobin. In the lungs haemoglobin combines with oxygen to form oxyhaemoglobin. In other organs oxyhaemoglobin splits up into haemoglobin and oxygen.

d) White blood cells have a nucleus. They form part of the body's defence system against microorganisms.

e) Platelets are small fragments of cells. They have no nucleus. Platelets help blood to clot at the site of a wound.

B3.2.3 Transport systems in plants

a) Flowering plants have separate transport systems:

  • xylem tissue transports water and mineral ions from the roots to the stem and leaves
  • the movement of water from the roots through the xylem and out of the leaves is called the transpiration stream
  • phloem tissue carries dissolved sugars from the leaves to the rest of the plant, including the growing regions and the storage organs.

Suggested ideas for practical work to develop skills and understanding include the following:

  • dissection of the heart
  • use software simulations of the work of the heart and blood vessels
  • observation of arteries and veins from slides
  • observation of blood smears
  • observation of valves in veins preventing backflow of blood using the 'athletic' arm / prominent vein
  • use sensors to measure blood pressure before, during and after exercise
  • investigate flow rate in xylem using celery, which can include calculation of flow rate
  • investigate the content of artificial phloem and xylem given knowledge of the appropriate tests
  • plan an investigation using a potometer to measure the effect of temperature or wind speed on the transpiration rate.

B3.3 Homeostasis

Humans need to remove waste products from their bodies to keep their internal environment relatively constant. People whose kidneys do not function properly may die because toxic substances accumulate in their blood. Their lives can be saved by using dialysis machines or having a healthy kidney transplanted. Water and ion content, body temperature and blood glucose levels must be kept within very narrow ranges.

Candidates should use their skills, knowledge and understanding to:

  • evaluate the advantages and disadvantages of treating kidney failure by dialysis or kidney transplant
  • evaluate modern methods of treating diabetes.

B3.3.1 Removal of waste and water control

a) Waste products that have to be removed from the body include:

  • carbon dioxide, produced by respiration and removed via the lungs when we breathe out
  • urea, produced in the liver by the breakdown of amino acids and removed by the kidneys in the urine, which is temporarily stored in the bladder.

b) If the water or ion content of the body is wrong, too much water may move into or out of the cells and damage them. Water and ions enter the body when we eat and drink.

c) A healthy kidney produces urine by:

  • first filtering the blood
  • reabsorbing all the sugar
  • reabsorbing the dissolved ions needed by the body
  • reabsorbing as much water as the body needs
  • releasing urea, excess ions and water as urine.

Additional guidance:

Knowledge of other parts of the urinary system, the structure of the kidney and the structure of a nephron is not required.

d) People who suffer from kidney failure may be treated either by using a kidney dialysis machine or by having a healthy kidney transplanted.

e) Treatment by dialysis restores the concentrations of dissolved substances in the blood to normal levels and has to be carried out at regular intervals.

f) In a dialysis machine a person's blood flows between partially permeable membranes. The dialysis fluid contains the same concentration of useful substances as the blood. This ensures that glucose and useful mineral ions are not lost. Urea passes out from the blood into the dialysis fluid.

g) In kidney transplants a diseased kidney is replaced with a healthy one from a donor. However, the donor kidney may be rejected by the immune system unless precautions are taken.

h) Antigens are proteins on the surface of cells. The recipient's antibodies may attack the antigens on the donor organ as they do not recognise them as part of the recipient's body.

i) To prevent rejection of the transplanted kidney:

  • a donor kidney with a 'tissue-type' similar to that of the recipient is used
  • the recipient is treated with drugs that suppress the immune system.

 Additional guidance:

Knowledge of the ABO blood grouping and compatibility tables is not required.

B3.3.2 Temperature control

a) Sweating helps to cool the body. More water is lost when it is hot, and more water has to be taken as drink or in food to balance this loss.

b) Body temperature is monitored and controlled by the thermoregulatory centre in the brain. This centre has receptors sensitive to the temperature of the blood flowing through the brain.

Additional guidance:

The name of the centre in the brain (hypothalamus) is not required.

c) Also temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature.

d) If the core body temperature is too high:

  • blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost
  • sweat glands release more sweat which cools the body as it evaporates.

Additional guidance:

HT only

FT candidates are not expected to describe details of changes in the blood vessels when the core body temperature is too high or too low but should understand that the skin looks red when we are hot due to increased blood flow.

e) If the core body temperature is too low:

  • blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries
  • muscles may 'shiver' – their contraction needs respiration, which releases some energy to warm the body.

Additional guidance:

HT only

B3.3.3 Sugar control

a) The blood glucose concentration of the body is monitored and controlled by the pancreas. The pancreas produces the hormone insulin, which allows the glucose to move from the blood into the cells.

b) A second hormone, glucagon, is produced in the pancreas when blood glucose levels fall. This causes glycogen to be converted into glucose and be released into the blood.

Additional guidance:

HT only

c) Type 1 diabetes is a disease in which a person's blood glucose concentration may rise to a high level because the pancreas does not produce enough of the hormone insulin.

d) Type 1 diabetes may be controlled by careful attention to diet, exercise, and by injecting insulin.

Suggested ideas for practical work to develop skills and understanding include the following:

  • use surface temperature sensors to monitor skin temperature in different conditions
  • plan an investigation to measure the cooling effect of sweating
  • demonstrate blood testing (using meters)
  • dissect and make observations of a kidney
  • design a model kidney dialysis machine using Visking tubing as the filter
  • test urine from diabetic and non-diabetic people using Clinistix.

B3.4 Humans and their environment

Humans often upset the balance of different populations in natural ecosystems, or change the environment so that some species find it difficult to survive. With so many people in the world, there is a serious danger of causing permanent damage not just to the local environments but also to the global environment unless our overall effect is managed carefully. Humans rely on ecosystems for food, water and shelter.

Candidates should use their skills, knowledge and understanding to:

  • analyse and interpret scientific data concerning environmental issues

Additional guidance:

Candidates will be given data to work from.

  • evaluate methods used to collect environmental data and consider their validity and reliability as evidence for environmental change
  • evaluate the methods being used to feed and provide water to an increasing human population, both in terms of short term and long term effects
  • evaluate the use of biogas generators

Additional guidance:

Candidates should have considered a number of biogas generator designs ranging from third-world generators supplying a single family to commercial generators. They should understand how the output from a biogas generator might be affected by climatic conditions.

  • evaluate the positive and negative effects of managing food production and distribution, and be able to recognise that practical solutions for human needs may require compromise between competing priorities.

Additional guidance:

Candidates should consider:

  • the differences in efficiency between producing food from animals and plants
  • the pros and cons of factory farming of animals
  • the implications of 'food miles'.

B3.4.1 Waste from human activity

a) Rapid growth in the human population and an increase in the standard of living means that increasingly more waste is produced. Unless waste is properly handled, more pollution will be caused.

b) Waste may pollute:

  • water, with sewage, fertiliser or toxic chemicals
  • air, with smoke and gases such as sulphur dioxide, which contributes to acid rain
  • land, with toxic chemicals such as pesticides and herbicides, which may be washed from the land into waterways.

c) Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste.

B3.4.2 Deforestation and the destruction of areas of peat

a) Large-scale deforestation in tropical areas, for timber and to provide land for agriculture, has:

  • increased the release of carbon dioxide into the atmosphere (because of burning and the activities of microorganisms)
  • reduced the rate at which carbon dioxide is removed from the atmosphere and 'locked up' for many years as wood.

b) Deforestation leads to reduction in biodiversity.

c) Deforestation has occurred so that:

  • crops can be grown from which biofuels, based on ethanol, can be produced
  • there can be increases in cattle and in rice fields to provide more food. These organisms produce methane and this has led to increases in methane in the atmosphere.

d) The destruction of peat bogs and other areas of peat releases carbon dioxide into the atmosphere.

Additional guidance:

Candidates should understand why 'peat free' composts are of increasing importance.

B3.4.3 Biofuels

a) Levels of carbon dioxide and methane in the atmosphere are increasing and contribute to 'global warming'. An increase in the Earth's temperature of only a few degrees Celsius:

  • may cause big changes in the Earth's climate
  • may cause a rise in sea level
  • may reduce biodiversity
  • may cause changes in migration patterns, eg in birds
  • may result in changes in the distribution of species.

b) Carbon dioxide can be sequestered in oceans, lakes and ponds and this is an important factor in removing carbon dioxide from the atmosphere.

c) Biofuels can be made from natural products by fermentation. Biogas, mainly methane, can be produced by anaerobic fermentation of a wide range of plant products or waste material containing carbohydrates.

B3.4.4 Food production

a) At each stage in a food chain, less material and less energy are contained in the biomass of the organisms. This means that the efficiency of food production can be improved by reducing the number of stages in food chains.

b) The efficiency of food production can also be improved by restricting energy loss from food animals by limiting their movement and by controlling the temperature of their surroundings.

c) Fish stocks in the oceans are declining. It is important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas. Net size and fishing quotas play an important role in conservation of fish stocks.

Additional guidance:

This is an example of sustainable food production.

d) The fungus Fusarium is useful for producing mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on glucose syrup, in aerobic conditions, and the biomass is harvested and purified.

Suggested ideas for practical work to develop skills and understanding include the following:

  • build a simple biogas generator to collect methane and demonstrate how the methane can be burned as a fuel
  • investigate and design a way of measuring the gas output of a biogas generator and compare the amount of gas produced by different materials.

3.4 Unit 2: Further Additional Science - Chemistry 3

C3.1 The periodic table

Throughout this unit candidates will be expected to write word equations for reactions specified. Higher Tier candidates will also be expected to write and balance symbol equations for reactions specified throughout the unit.

C3.1 The periodic table 

The modern periodic table has been developed from work begun by Newlands and Mendeleev. There are trends in chemical properties within the periodic table linked to how easily the element gains or loses electrons.

Candidates should use their skills, knowledge and understanding to:

  • evaluate the work of Newlands and Mendeleev in terms of their contributions to the development of the modern periodic table

Additional guidance:

Knowledge of the history of the periodic table is limited to that specified in the subject content.

Candidates may consider other models, but knowledge is limited to the work of Newlands and Mendeleev. Examination questions would give information about other models so that comparisons can be made.

  • explain why scientists regarded a periodic table of the elements first as a curiosity, then as a useful tool and finally as an important summary of the structure of atoms.

C3.1.1 The early periodic table

a) Newlands, and then Mendeleev, attempted to classify the elements by arranging them in order of their atomic weights. The list can be arranged in a table so that elements with similar properties are in columns, known as groups. The table is called a periodic table because similar properties occur at regular intervals.

b) The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed. Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered.

C3.1.2 The modern periodic table

a) When electrons, protons and neutrons were discovered early in the 20th century, the periodic table was arranged in order of atomic (proton) numbers. When this was done, all elements were placed in appropriate groups.

b) The modern periodic table can be seen as an arrangement of the elements in terms of their electronic structures. Elements in the same group have the same number of electrons in their highest occupied energy level (outer shell).

Additional guidance:

The periodic table that will be used in the examinations is on the Data Sheet, with main groups numbered from 1 to 7 and the noble gases as Group 0.

Candidates are not expected to know detailed electronic configurations for elements beyond calcium, but should understand that the number of electrons in the highest occupied energy level (outer shell) for elements in the main groups is equal to the group number.

C3.1.3 Trends within the periodic table

a) The elements in Group 1 of the periodic table (known as the alkali metals):

  • are metals with low density (the first three elements in the group are less dense than water)
  • react with non-metals to form ionic compounds in which the metal ion carries a charge of +1. The compounds are white solids that dissolve in water to form colourless solutions
  • react with water, releasing hydrogen
  • form hydroxides that dissolve in water to give alkaline solutions.

b) In Group 1, the further down the group an element is:

  • the more reactive the element
  • the lower its melting point and boiling point.

c) Compared with the elements in Group 1, transition elements:

  • have higher melting points (except for mercury) and higher densities
  • are stronger and harder
  • are much less reactive and so do not react as vigorously with water or oxygen.

d) Many transition elements have ions with different charges, form coloured compounds and are useful as catalysts.

e) The elements in Group 7 of the periodic table (known as the halogens) react with metals to form ionic compounds in which the halide ion carries a charge of –1.

f) In Group 7, the further down the group an element is:

  • the less reactive the element
  • the higher its melting point and boiling point.

g) A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.

h) The trends in reactivity within groups in the periodic table can be explained because the higher the energy level of the outer electrons:

  • the more easily electrons are lost
  • the less easily electrons are gained.

Additional guidance:

HT only

Suggested ideas for practical work to develop skills and understanding include the following:

  • demonstration of the combustion of reactions of sodium and potassium
  • demonstration of the reactions of sodium and potassium with chlorine
  • demonstration of the reactions of lithium, sodium and potassium with water
  • demonstration of the reactions of the halogens with iron wool
  • investigation of the displacement of halogens from solutions of their salts by more reactive halogens
  • heating transition metals in air (any of Ti, Cr, Co, Ni, Fe, Cu) to compare reactivity and melting points with Group 1
  • demonstration of the reaction of iron wool with steam
  • observation of as many salts of transition metals as possible (bottles with formulae clearly displayed)
  • demonstrations of transition metals and their salts as catalysts
  • investigation of the catalysis of hydrogen peroxide decomposition by different transition metals and their compounds.

C3.2 Water

C3.2 Water

The water we drink is not pure water because it contains dissolved substances. It should be safe to drink water that has been treated. This means that the water does not contain anything that could cause us harm. Some of the dissolved substances are beneficial to our health but some cause hard water.

Candidates should use their skills, knowledge and understanding to:

  • evaluate the use of commercial water softeners
  • consider and evaluate the environmental, social and economic aspects of water quality and hardness

Additional guidance:

Candidates may be asked to evaluate different methods of softening water, or of providing drinking water of sufficient quality.

  • consider the advantages and disadvantages of adding chlorine and fluoride to drinking water.

Additional guidance: 

Candidates will be expected to interpret and evaluate information and data that is provided in questions set within these contexts.

C3.2.1 Hard and soft water

a) Soft water readily forms lather with soap. Hard water reacts with soap to form scum and so more soap is needed to form lather. Soapless detergents do not form scum.

Additional guidance:

Candidates should be able to measure the hardness of water by titration with soap solution.

b) Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when water comes into contact with rocks.

c) There are two types of hard water. Permanent hard water remains hard when it is boiled. Temporary hard water is softened by boiling.

Additional guidance:

Candidates should be able to distinguish between temporary hard water and permanent hard water.

d) Higher tier only: Temporary hard water contains hydrogencarbonate ions (HCO3 ¯) that decompose on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates.

e) Using hard water can increase costs because more soap is needed. When temporary hard water is heated it can produce scale that reduces the efficiency of heating systems and kettles.

f) Hard water has some benefits because calcium compounds are good for the development and maintenance of bones and teeth and also help to reduce heart disease.

g) Hard water can be made soft by removing the dissolved calcium and magnesium ions. This can be done by:

  • adding sodium carbonate, which reacts with the calcium and magnesium ions to form a precipitate of calcium carbonate and magnesium carbonate
  • using commercial water softeners such as ion exchange columns containing hydrogen ions or sodium ions, which replace the calcium and magnesium ions when hard water passes through the column.

C3.2.2 Purifying water

a) Water of the correct quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes.

Additional guidance:

Water of the correct quality is produced by:

  • choosing an appropriate source
  • passing the water through filter beds to remove any solids
  • sterilising with chlorine.

b) Water filters containing carbon, silver and ion exchange resins can remove some dissolved substances from tap water to improve the taste and quality.

Additional guidance:

Detailed knowledge of specific water filters is not required.

Examination questions may give information about water filters so that comparisons can be made.

Candidates should understand the principles of how ion exchange resins work but do not need detailed knowledge of the structure or chemical nature of specific resins.

c) Chlorine may be added to drinking water to reduce microbes and fluoride may be added to improve dental health.

Additional guidance:

Candidates should be aware of the arguments for and against the addition of fluoride to drinking water.

d) Pure water can be produced by distillation.

Additional guidance:

Candidates should be aware of the large amount of energy needed for distillation and, as a consequence, of the high costs involved.

Suggested ideas for practical work to develop skills and understanding include the following:

  • investigation of which ions cause hard water, eg adding soap solution to solutions of NaCl, CaCl2, KCl, and MgCl2
  • making temporary hard water by adding excess carbon dioxide to limewater
  • determining hardness of samples of water – shake with soap solution – measuring cm3 of soap to get permanent lather
  • the removal of hardness:
    • temporary hardness: test before and after boiling, with soap
    • permanent hardness: test before and after addition of sodium carbonate
  • testing hard water before and after passing through an ion exchange column
  • using conductivity sensors to analyse different samples of hard and soft water
  • design and carry out an investigation to compare the effectiveness of commercial water softeners using soap titration
  • investigating the various types of water 'filters' that are commercially available
  • distillation of seawater - design a simple apparatus to do the distillation and check the quality of the distillate (boiling point and evaporation to dryness of a sample on a watch glass).

C3.3 Calculating and explaining energy change

C3.3 Calculating and explaining energy change

Knowing the amount of energy involved in chemical reactions is useful so that resources are used efficiently and economically. It is possible to measure the amount of energy experimentally or to calculate it.

Candidates should use their skills, knowledge and understanding to:

  • consider the social, economic and environmental consequences of using fuels

Additional guidance:

Candidates may be provided with information for comparison and evaluation. For example, they may be given information about the ingredients of a particular food or the components of a fuel, but will not be expected to have knowledge of the constituents of commercial products beyond that specified in the subject content for this unit.

  • interpret simple energy level diagrams in terms of bond breaking and bond formation (including the idea of activation energy and the effect on this of catalysts)
  • evaluate the use of hydrogen to power cars compared to other fuels

C3.3.1 Energy from reactions

a) The relative amounts of energy released when substances burn can be measured by simple calorimetry, eg by heating water in a glass or metal container. This method can be used to compare the amount of energy released by fuels and foods.

Additional guidance:

Candidates should be able to calculate and compare the amount of energy released by different fuels given the equation:

Q = mc ΔT

b) Energy is normally measured in joules (J).

Additional guidance:

For comparison purposes, energy values could be given in kJ or calories for a given mass or amount of substance, eg calories per gram, kJ per mole or kJ per gram. If candidates are required to convert from calories to joules, the conversion factor will be given in questions.

c) The amount of energy released or absorbed by a chemical reaction in solution can be calculated from the measured temperature change of the solution when the reagents are mixed in an insulated container. This method can be used for reactions of solids with water or for neutralisation reactions.

d) Simple energy level diagrams can be used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction.

Additional guidance:

Candidates will be expected to understand simple energy level diagrams showing the relative energies of reactants and products, the activation energy and the overall energy change, with a curved arrow to show the energy as the reaction proceeds. Candidates should be able to relate these to exothermic and endothermic reactions.

e) During a chemical reaction:

  • energy must be supplied to break bonds
  • energy is released when bonds are formed.

f) Higher tier only: In an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds.

Additional guidance:

Candidates should be able to calculate the energy transferred in reactions using supplied bond energies.

g) Higher tier only: In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds.

h) Catalysts provide a different pathway for a chemical reaction that has a lower activation energy.

Additional guidance:

Candidates should be able to represent the effect of a catalyst on an energy level diagram.

i) Hydrogen can be burned as a fuel in combustion engines.

hydrogen + oxygen ----> water

It can also be used in fuel cells that produce electricity to power vehicles.

Additional guidance:

Knowledge of the details of the reactions in fuel cells is not required. Candidates should be able to compare the advantages and disadvantages of the combustion of hydrogen fuel cells from information that is provided.

Suggested ideas for practical work to develop skills and understanding include the following:

  • design an investigation to compare the energy produced by different liquid fuels and different foods using a simple calorimeter
  • measuring and calculating the energy change for exothermic reactions (eg react acid with Mg ribbon) and endothermic reactions (eg dissolving potassium nitrate)  
  • carrying out some reactions and measuring the energy produced, assuming that it is only the water in the solution that is being heated and that 4.2 joules will raise the temperature of 1cm3 of water by 1°C.

C3.4 Further analysis and quantitative chemistry

C3.4 Further analysis and quantitative chemistry

A range of chemical tests can be used for the detection and identification of elements and compounds. Titrations can be used to find the amounts of acid or alkali in a solution.

Candidates should use their skills, knowledge and understanding to:

  • interpret results of the chemical tests in this specification

Additional guidance:

Candidates are expected to know the chemical tests specified in the subject content and may be asked to interpret results of any of those tests applied to solutions or mixtures of substances in different contexts.

  • interpret and evaluate the results of analyses carried out to identify elements and compounds for forensic, health or environmental purposes.

Additional guidance:

Candidates should be able to comment on results and data from such analyses that are presented to them. This will not include interpretation of detailed information that uses knowledge beyond that expected at GCSE.

C3.4.1 Analysing substances

a) Flame tests can be used to identify metal ions. Lithium, sodium, potassium, calcium and barium compounds produce distinctive colours in flame tests:

  • lithium compounds result in a crimson flame
  • sodium compounds result in a yellow flame
  • potassium compounds result in a lilac flame
  • calcium compounds result in a red flame
  • barium compounds result in a green flame.

Additional guidance:

Flame colours of other metal ions are not required knowledge.

b) Aluminium, calcium and magnesium ions form white precipitates with sodium hydroxide solution but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution.

c) Copper(II), iron(II) and iron(III) ions form coloured precipitates with sodium hydroxide solution. Copper forms a blue precipitate, iron(II) a green precipitate and iron(III) a brown precipitate.

d) Carbonates react with dilute acids to form carbon dioxide. Carbon dioxide produces a white precipitate with limewater. This turns limewater cloudy.

e) Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid. Silver chloride is white, silver bromide is cream and silver iodide is yellow.

f) Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid.

g) The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator.

Additional guidance:

Candidates should be able to carry out titrations using strong acids and strong alkalis only (sulfuric, hydrochloric and nitric acids only).

h) Higher tier only: If the concentration of one of the reactants is known, the results of a titration can be used to find the concentration of the other reactant.

Additional guidance:

Candidates should be able to calculate the chemical quantities in titrations involving concentrations (in moles per dm3) and masses (in grams per dm3).

Suggested ideas for practical work to develop skills and understanding include the following:

  • flame tests – spray solution into flame or use wooden splints soaked in solutions overnight or use nichrome wire loops
  • try tests using mixtures of two salts, eg flame tests on solutions containing pairs of the listed ions
  • Fe2+ with sodium hydroxide solution – note that the initial colour is quickly oxidised
  • react carbonates with acid and test the gas for CO2 using a drop of limewater on a glass rod
  • distinguishing between the halide ions using silver nitrate solution
  • identifying unknown single salts using the tests in the content
  • plan a suitable order of tests to use on a solution that contains an unknown single salt
  • strong acid/strong alkali titrations (HCl/NaOH) to find unknown concentration (using indicators and pH sensors to determine titration endpoints).

C3.5 The production of ammonia

C3.5 The production of ammonia

In industrial processes, energy requirements and emissions need to be considered both for economic reasons and for sustainable development.

Candidates should use their skills, knowledge and understanding to:

  • evaluate the conditions necessary in an industrial process to maximise yield and minimise environmental impact
  • Higher tier only: describe and evaluate the effects of changing the conditions of temperature and pressure on a given reaction or process
  • evaluate the conditions used in industrial processes in terms of energy requirements.

C3.5.1 Making ammonia

a) The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources.

b) The purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres). Some of the hydrogen and nitrogen reacts to form ammonia. The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen:

On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled.

c) Higher tier only: When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.

d) Higher tier only: The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.

e) Higher tier only: If the temperature is raised, the yield from the endothermic reaction increases and the yield from the exothermic reaction decreases.

f) Higher tier only: If the temperature is lowered, the yield from the endothermic reaction decreases and the yield from the exothermic reaction increases.

g) Higher tier only: In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.

h)Higher tier only: These factors, together with reaction rates, are important when determining the optimum conditions in industrial processes, including the Haber process.

Suggested ideas for practical work to develop skills and understanding include the following:

  • demonstration of the effect of adding acid and then alkali to bromine water to show the effect of changing conditions on equilibrium
  • investigation of the effect of adding acid and then alkali to a solution of potassium chromate
  • modelling dynamic equilibrium with two 25cm3 measuring cylinders, each with an open-ended glass tube but with different diameters. Put 25cm3 of water into one cylinder. Transfer water from one cylinder to the other using a finger over the end of each tube in turn (keep the tubes in the same cylinder) until the level in each cylinder does not change any more
  • demonstration of effect of temperature and pressure on equilibrium using 50cm3 of NO2/N2O4 in a gas syringe.

C3.6 Alcohols, carboxylic acids and esters

C3.6 Alcohols, carboxylic acids and esters

Alcohols and carboxylic acids are important organic chemicals that have many uses. Alcohols react with carboxylic acids to produce esters.

Candidates should use their skills, knowledge and understanding to:

  • represent the structures of alcohols in the following forms:

structure of alcohols

  • represent the structures of carboxylic acids in the following forms:

structure of carboxylic acids

CH3COOH

  • evaluate the social and economic advantages and disadvantages of the uses of alcohols, carboxylic acids and esters.

Additional guidance:

Candidates may be given information and data about alcohols, carboxylic acids and esters for comparison and evaluation in the examination.

C3.6.1 Alcohols

a) Alcohols contain the functional group –OH. Methanol, ethanol and propanol are the first three members of a homologous series of alcohols.

Additional guidance:

Candidates should be able to recognise alcohols from their names or formulae, but do not need to know the names of individual alcohols, other than methanol, ethanol and propanol.

b) Methanol, ethanol and propanol:

  • dissolve in water to form a neutral solution
  • react with sodium to produce hydrogen
  • burn in air
  • are used as fuels and solvents, and ethanol is the main alcohol in alcoholic drinks.

Additional guidance:

Candidates are not expected to write balanced chemical equations for the reactions of alcohols other than combustion reactions.

c) Ethanol can be oxidised to ethanoic acid, either by chemical oxidising agents or by microbial action. Ethanoic acid is the main acid in vinegar.

Additional guidance:

Candidates should be aware that vinegar is an aqueous solution that contains ethanoic acid.

C3.6.2 Carboxylic acids

a) Ethanoic acid is a member of the carboxylic acids, which have the functional group –COOH.

Additional guidance:

Candidates should be able to recognise carboxylic acids from their names or formulae, but do not need to know the names of individual carboxylic acids, other than methanoic acid, ethanoic acid and propanoic acid.

b) Carboxylic acids:

  • dissolve in water to produce acidic solutions
  • react with carbonates to produce carbon dioxide
  • react with alcohols in the presence of an acid catalyst to produce esters
  • Higher tier only: do not ionise completely when dissolved in water and so are weak acids
  • Higher tier only: aqueous solutions of weak acids have a higher pH value than aqueous solutions of strong acids with the same concentration.

Additional guidance:

Candidates are not expected to write balanced chemical equations for the reactions of carboxylic acids.

C3.6.3 Esters

a) Ethyl ethanoate is the ester produced from ethanol and ethanoic acid. Esters have the functional group –COO–. They are volatile compounds with distinctive smells and are used as flavourings and perfumes.

Additional guidance:

Candidates will not be expected to give the names of esters other than ethyl ethanoate, but should be able to recognise a compound as an ester from its name or its structural formula.

Suggested ideas for practical work to develop skills and understanding include the following:

  • investigation of the reactions of ethanol
  • comparison of properties of ethanol with water
  • oxidation of ethanol using aqueous potassium dichromate
  • design and carry out an investigation of the oxidation of dilute solutions of ethanol (eg wine or beer) by exposing to the air for several days
  • comparison of the reactions of methanol, ethanol and propanol
  • investigation of the reactions of ethanoic acid
  • distinguishing between samples of ethanol, ethanoic acid and ethyl ethanoate using simple chemical tests
  • preparation of ethyl ethanoate using ethanol and ethanoic acid with sulfuric acid as a catalyst. Recognise the ester by smell after neutralising the acid with sodium hydrogen carbonate
  • add drops of esters to water to smell more effectively.

3.5 Unit 3: Further Additional Science - Physics 3

P3.1 Medical applications of physics

P3.1 Medical applications of physics

Physics has many applications in the field of medicine. These include the uses of X-rays and ultrasound for scanning, and of light for image formation with lenses and endoscopes

Candidates should use their skills, knowledge and understanding to:

  • draw and interpret ray diagrams in order to determine the nature of the image

  • Additional guidance:

    In ray diagrams a convex lens will be represented by: a convex lens
    A concave lens will be represented by: a concave lens

  • evaluate the use of different lenses for the correction of defects of vision
  • compare the medical use of ultrasound and X rays

  • Additional guidance:

    Candidates should understand that some of the differences in use are because ultrasound waves are
    non-ionising and X rays are ionising.

  • evaluate the advantages and disadvantages of using ultrasound, X-rays and Computerised Tomography (CT) scans.

  • Additional guidance:

    Limited to safety issues and the quality of image formed.

    P3.1.1 X-rays

    a) X-rays are part of the electromagnetic spectrum. They have a very short wavelength and cause ionisation.

    Additional guidance:

    Properties of X-rays include:

    • they affect a photographic film in the same way as light
    • they are absorbed by metal and bone
    • they are transmitted by soft tissue
    • their wavelength is of the same order of magnitude as the diameter of an atom.

    b) X-rays can be used to diagnose and treat some medical conditions.

    Additional guidance:

    Examples include CT scans, bone fractures, dental problems and killing cancer cells.

    The use of charge-coupled devices (CCDs) allows images to be formed electronically.

    c) Precautions to be taken when X-ray machines and CT scanners are in use.

    P3.1.2 Ultrasound

    a) Electronic systems can be used to produce ultrasound waves, which have a frequency higher than the upper limit of hearing for humans.

    Additional guidance:

    Candidates should know that the range of human hearing is about 20 Hz to 20 000 Hz.

    b) Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is.

    c) Calculation of the distance between interfaces in various media.

    Additional guidance: 

    Candidates may be required to use data from diagrams of oscilloscope traces.

    • s is distance in metres, m
    • v is speed in metres per second, m/s
    • t is time in seconds, s

    d) Ultrasound waves can be used in medicine.

    Additional guidance:

    Examples include pre-natal scanning and the removal of kidney stones.

    P3.1.3 Lenses

    a) Refraction is the change of direction of light as it passes from one medium to another.

    b) A lens forms an image by refracting light.

    c) In a convex or converging lens, parallel rays of light are brought to a focus at the principal focus. The distance from the lens to the principal focus is called the focal length.

    Additional guidance:

    • i is the angle of incidence
    • r is the angle of refraction

    d) The nature of an image is defined by its size relative to the object, whether it is upright or inverted relative to the object and whether it is real or virtual.

    e) The nature of the image produced by a converging lens for an object placed at different distances from the lens.

    f) The use of a converging lens as a magnifying glass.

    g) The nature of the image produced by a concave or diverging lens.

    h) The construction of ray diagrams to show the formation of images by converging and diverging lenses.

    Additional guidance:

    Candidates may be asked to complete ray diagrams drawn on graph paper

    i) The magnification produced by a lens is calculated using the equation:

    P3.1.4 The eye

    a) The structure of the eye. The structure of the eye is limited to:

    • retina
    • lens
    • cornea
    • pupil /iris
    • ciliary muscle
    • suspensory ligaments. 

    Additional guidance:

    Candidates should know the function of these named parts.

    Candidates should understand how the action of the ciliary muscle causes changes in the shape of the lens, which allows the light to be focused at varying distances.

    b) Correction of vision using convex and concave lenses to produce an image on the retina:

    • long sight, caused by the eyeball being too short, or the eye lens being unable to focus
    • short sight, caused by the eyeball being too long, or the eye lens being unable to focus.

    c) Range of vision. The eye can focus on objects between the near point and the far point.

    Additional guidance:

    Candidates should know that the near point is approximately 25 cm and the far point is infinity.

    d) Comparison between the structure of the eye and the camera.

    Additional guidance:

    Candidates should be aware that the film in a camera or the CCDs in a digital camera is the equivalent of the retina in the eye.

    e) The power of a lens is given by:

    Additional guidance:

    Candidates should know that the power of a converging lens is positive and the power of a diverging lens is negative.

    • P is power in dioptres, D
    • f is focal length in metres, m

    f) The focal length of a lens is determined by:

    • the refractive index of the material from which the lens is made, and
    • the curvature of the two surfaces of the lens.

    g) Higher Tier only: For a given focal length, the greater the refractive index, the flatter the lens. This means that the lens can be manufactured thinner.

    P3.1.5 Other applications using light

    a) Total internal reflection and critical angle.

    Additional guidance:

    Candidates need to understand the concept of critical angle but knowledge of the values of critical angles is not required.

    Higher Tier only: c is the critical angle

    b) Visible light can be sent along optical fibres.

    Additional guidance:

    Examples of use should include the endoscope for internal imaging.

    c) The laser as an energy source for cutting, cauterising and burning.

    Additional guidance:

    Knowledge of how lasers work is not required. Applications should include use in eye surgery.

    Suggested ideas for practical work to develop skills and understanding include the following:

    • demonstrating the range of frequencies audible to the human ear, using a signal generator, loudspeaker and oscilloscope
    • demonstrating long and short sight by placing a screen, not at the focal point, and rectifying the image through the use of appropriate lenses
    • using a round bottom flask filled with a solution of fluorescein to represent the eye
    • investigating total internal reflection using a semi-circular glass block.

    P3.2 Using physics to make things work

    P3.2 Using physics to make things work

    Many things, from simple toys to complex fairground rides, are constructed from basic machines such as the lever. A knowledge of the physics involved in balancing and turning can help us to make these appliances work.

    Candidates should use their skills, knowledge and understanding to:

  • analyse the stability of objects by evaluating their tendency to topple
  • Additional guidance:

    Candidates should use a range of laboratory equipment to model real-life situations, eg cranes.

  • recognise the factors that affect the stability of an object
  • Additional guidance:

    Candidates should recognise that objects with a wide base and low centre of mass are more stable than those with a narrow base and a high centre of mass.

  • evaluate how the design of objects affects their stability
  • interpret and evaluate data on objects moving in circular paths.
  • Additional guidance:

    Candidates should understand that a centripetal force does not exist in its own right but is always provided by something else such as gravitational force, fiction or tension.

    P3.2.1 Centre of mass

    a) The centre of mass of an object is that point at which the mass of the object may be thought to be concentrated.

    Additional guidance:

    Candidates will be expected to be able to describe how to find the centre of mass of a thin, irregular sheet of a material.

    b) If freely suspended, an object will come to rest with its centre of mass directly below the point of suspension.

    c) The centre of mass of a symmetrical object is along the axis of symmetry.

    d) For a simple pendulum:

    Additional guidance:

    • T is periodic time in seconds, s
    • f is frequency in hertz, Hz

    e) The time period depends on the length of a pendulum.

    Additional guidance:

    The equation is not required.

    Applications of the pendulum should include simple fairground and playground rides.

    P3.2.2 Moments

    a) The turning effect of a force is called the moment.

    b) The size of the moment is given by the equation:

    Additional guidance:

    • M is the moment of the force in newton-metres, Nm
    • F is the force in newtons, N
    • d is the perpendicular distance from the line of action of the force to the pivot in metres, m

    c) If an object is not turning, the total clockwise moment must be exactly balanced by the total anticlockwise moment about any pivot.

    d) Higher Tier only: The calculation of the size of a force, or its distance from pivot, acting on an object that is balanced.

    e) Ideas of simple levers.

    Additional guidance:

    Limited to levers as force multipliers.

    f) Higher Tier only: If the line of action of the weight of an object lies outside the base of the object there will be a resultant moment and the body will tend to topple.

    Additional guidance:

    Applications should include vehicles and simple balancing toys.

    P3.2.3 Hydraulics

    a) Liquids are virtually incompressible, and the pressure in a liquid is transmitted equally in all directions.

    Additional guidance:

    Candidates should understand that this means that a force exerted at one point on a liquid will be transmitted to other points in the liquid.

    b) The use of different cross-sectional areas on the effort and load side of a hydraulic system enables the system to be used as a force multiplier.

    c) The pressure in different parts of a hydraulic system is given by:

    Additional guidance:

    • P is the pressure in pascals, Pa
    • F is the force in newtons, N
    • A is the cross-sectional area in metres squared, m2

    P3.2.4 Circular motion

    a) When an object moves in a circle it continuously accelerates towards the centre of the circle. This acceleration changes the direction of motion of the body, not its speed.

    b) The resultant force causing this acceleration is called the centripetal force and is always directed towards the centre of the circle.

    Additional guidance:

    Candidates should be able to identify which force(s) provide(s) the centripetal force in a given situation.

    c) The centripetal force needed to make an object perform circular motion increases as:

    • the mass of the object increases
    • the speed of the object increases
    • the radius of the circle decreases.

    Additional guidance:

    The equation is not required.

    Suggested ideas for practical work to develop skills and understanding include the following:

    • demonstrating that pressure in liquids acts in all directions using a circular container with holes around it
    • finding the centre of mass of an irregularly shaped card
    • using a balanced metre ruler and masses to verify the principle of moments
    • plan and carry out an investigation into factors that affect the period of a simple pendulum (mass, length of pendulum, amplitude of swing)
    • whirling a bung on the end of a piece of string to demonstrate the factors that affect centripetal force
    • investigating objects and slopes to find out the point at which the object topples.

    P3.3 Keeping things moving

    P3.3 Keeping things moving

    Electric currents produce magnetic fields. Forces produced in magnetic fields can be used to make things move. This is called the motor effect and is how appliances such as the electric motor create movement.

    Many appliances do not use 230 volts mains electricity. Transformers are used to provide the required potential difference.

    Candidates should use their skills, knowledge and understanding to:

    • interpret diagrams of electromagnetic appliances in order to explain how they work
    • compare the use of different types of transformer for a particular application.

    Additional guidance:

    Examples might include some mobile phone chargers and power supplies for lap top computers.

    P3.3.1 The motor effect

    a) When a current flows through a wire a magnetic field is produced around the wire.

    Additional guidance:

    Applications of electromagnets could include their use on cranes for lifting iron/ steel.

    b) The motor effect and its use.

    Additional guidance:

    Candidates should be able to apply the principles of the motor effect in any given situation.

    c) The size of the force can be increased by:

    • increasing the strength of the magnetic field
    • increasing the size of the current.

    Additional guidance:

    The equation F = BIL is not required.

    d) The conductor will not experience a force if it is parallel to the magnetic field.

    e) The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed.

    Additional guidance:

    Candidates will be expected to identify the direction of the force using Fleming's left-hand rule.

    P3.3.2 Transformers

    a) If an electrical conductor 'cuts' through a magnetic field a potential difference is induced across the ends of the conductor.

    b) If a magnet is moved into a coil of wire a potential difference is induced across the ends of the coil.

    c) The basic structure of the transformer.

    d) An alternating current in the primary coil produces a changing magnetic field in the iron core and hence in the secondary coil. This induces an alternating potential difference across the ends of the secondary coil.

    Additional guidance:

    Knowledge of laminations and eddy currents in the core are not required.

    e) In a step-up transformer the potential difference across the secondary coil is greater than the potential difference across the primary coil.

    f) In a step-down transformer the potential difference across the secondary coil is less than the potential difference across the primary coil.

    g) The potential difference across the primary and secondary coils of a transformer are related by the equation:

    Additional guidance:

    • Vp is the potential difference across the primary coil in volts, V
    • Vs is the potential difference across the secondary coil in volts, V
    • np is the number of turns on the primary coil
    • ns is the number of turns on the secondary coil

    h) If transformers are assumed to be 100% efficient, the electrical power output would equal the electrical power input.

    Additional guidance:

    Candidates should be aware that the input to a transformer is determined by the required output.

    • Vp is the potential difference across the primary coil in volts, V
    • Ip is the current in the primary coil in amperes (amps), A
    • Vs is the potential difference across the secondary coil in volts, V
    • Is is the current in the secondary coil in amperes (amps), A

    i) Switch mode transformers operate at a high frequency, often between 50 kHz and 200 kHz.

    j) Switch mode transformers are much lighter and smaller than traditional transformers working from a 50 Hz mains supply.

    Additional guidance:

    Candidates should be aware that this makes them useful for applications such as mobile phone chargers.

    k) Switch mode transformers use very little power when they are switched on but no load is applied.

    Suggested ideas for practical work to develop skills and understanding include the following:

    • placing a foil strip with a current going through it in a strong magnetic field
    • building a motor
    • making a loudspeaker
    • making a transformer using C cores and insulated wire
    • demonstrating a transformer to show the difference between using d.c. and a.c.

    3.6 Unit 4 - Controlled Assessment

    3.6.1 Introduction

    3.6.1 Introduction

    This unit is assessed by Controlled Assessment. It is worth 25% of the total marks and consists of a minimum of one practical investigation based on topics in the specification.

    Access arrangements (see sections 4.5 and 5.4) can enable candidates with special needs to undertake this assessment.

    Teachers are encouraged to undertake a wide range of practical and investigative work, including fieldwork, with their candidates. We take the view that it is not good practice to do practical work only for the Controlled Assessment. As teachers know well, candidates enjoy and are motivated by practical work. Throughout this specification we have given many examples of practical work supporting the science content. Full details of this practical work are included in our resources package.

    In this unit, candidates use a range of practical skills and knowledge in one investigation chosen from those supplied by AQA. The investigations are based on topics in the specification. Guidance for teachers will be given with each investigation. Every year, three Controlled Assessments will be available; one for each unit. Each task assesses How Science Works skills, not candidates' knowledge and understanding of the science context.

    The right-hand column of the tables below shows the Assessment Focus thread from National Strategies APP (Assessing Pupils' Progress). This will enable teachers to ensure progression from KS3 to KS4.

    FAS4.1 Plan practical ways to develop and test candidate's own scientific explanation

    Candidates should be able to:
    FAS4.1.1 Develop hypotheses and plan practical ways to test them, by:Additional guidance: AF/thread
    a) being able to develop a hypothesisCandidates should be able to suggest the outcome of an investigation.1/4
    b) being able to test hypothesesCandidates should be able to plan a fair test to investigate their hypothesis.1/4
    c) using appropriate technology.Candidates should appreciate that technology such as data logging may provide a better means of obtaining data. They should be able to suggest appropriate technology for collecting data and explain why a particular technological method is the most appropriate. Candidates should use ICT whenever appropriate.4/1

    FAS4.2 Assess and manage risks when carrying out practical work

     Candidates should be able to:

    FAS4.2.1 assess and manage risks when carrying out practical work, by:Additional guidance:AF/thread
    a) identifying some possible hazards in practical situationsCandidates will be expected to independently recognise a range of familiar hazards and consult appropriate resources and expert advice.4/4
    b) suggest ways of managing risks.Candidates should assess risks to themselves and others and take action to reduce these risks by adapting their approaches to practical work in order to control risk.4/4

    FAS4.3 Collect primary and secondary data

     Candidates should be able to:

    C4.3.1 make observations, by:AF/thread
    a) carrying out practical work and research, and using the data collected to develop hypotheses.4/3
    FAS4.3.1 demonstrate an understanding of the need to acquire high-quality data, by:Additional guidance:AF/thread
    a) appreciating that, unless certain variables are controlled, the results may not be validCandidates should be able to explain whether results can be considered valid and recognise when an instrument or technique might not be measuring the variable intended.4/3
    b) identifying when repeats are needed in order to improve reproducibilityCandidates should recognise that a second set of readings with another instrument or by a different observer could be used to cross check results.4/3
    c) recognising the value of further readings to establish repeatability and accuracyCandidates should understand that accuracy is a measure of how close the measured value is to the true value.4/3
    d) considering the resolution of the measuring deviceCandidates should be able to explain that resolution is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the indication (output).4/3
    e) considering the precision of the measured data where precision is indicated by the degree of scatter from the mean.Candidates should be able to distinguish between accuracy and precision when applied to an instrument's readings4/3
    f) identifying the range of the measured data.Candidates should be able to identify the upper and lower limits of the range and be able to identify which extra results, within or outside the range would be appropriate.4/3

    FAS4.4 Select and process primary and secondary data

     Candidates should be able to:

    FAS4.4.1 show an understanding of the value of means, by:Additional guidance:AF/thread
    a) appreciating when it is appropriate to calculate a mean 5/1
    b) calculating the mean of a set of at least three results.Candidates should be able to recognise the need to exclude anomalies before calculating means to an appropriate number of decimal places.5/1
    FAS4.4.2 demonstrate an understanding of how data may be displayed, by:Additional guidance: AF/thread
    a) drawing tablesCandidates should be able to draw up a table of two or more columns, with correct headings and units, adequately representing the data obtained.3/2
    b) drawing charts and graphsCandidates should be able to construct an appropriate graphical representation of the data such as a bar chart or line graph and draw a line of best fit when appropriate. Candidates may use ICT to produce their graphs or charts.3/2
    c) choosing the most appropriate form of presentation.Candidates should be able to identify the most appropriate method of display for any given set of data.3/1

    FAS4.5 Analyse and interpret primary and secondary data

     Candidates should be able to:

    FAS4.5.1 distinguish between a fact and an opinion, by:Additional guidance: AF/thread
    a) recognising that an opinion might be influenced by factors other than scientific factCandidates should recognise that the opinion may be influenced by economic, ethical, moral, social or cultural considerations.2/1
    b) identifying scientific evidence that supports an opinion. 1/2
    FAS4.5.2 review methodology to assess fitness for purpose, by:Additional guidance:AF/thread
    a) identifying causes of variation in dataCandidates should be able to identify from data whether there is any variation other than obvious anomalies, and identify a potential cause for variation or uncertainty.5/2
    b) recognising and identifying the cause of random errors. If a data set contains random errors, repeating the readings and calculating a new mean can reduce their effectCandidates should appreciate that human error might be the cause of inaccurate measurements and explain how human error might have influenced the accuracy of a measurement or might have introduced bias into a set of readings.5/2
    c) recognising and identifying the cause of anomalous resultsCandidates should be able to identify anomalous results and suggest what should be done about them.5/2
    d) recognising and identifying the cause of systematic errors.Candidates should be able to identify when a data set contains a systematic error and appreciate that repeat readings cannot reduce the effect of systematic errors. Candidates should realise that a zero error is a 5/2 type of systematic error. Candidates should be able to identify if a scale has been incorrectly used and suggest how to compensate for a zero error.5/2
    FAS4.5.3 identify patterns in data, by:Additional guidance: AF/thread
    a) describing the relationship between two variables and deciding whether the relationship is causal or by association.Candidates should be able to use terms such as linear or directly proportional, or describe a complex relationship.5/3
    FAS4.5.4 draw conclusions using scientific ideas and evidence, by:Additional guidance: AF/thread
    a) writing a conclusion, based on evidence that relates correctly to known factsCandidates should be able to state simply what the evidence shows to justify a conclusion, and recognise the limitations of evidence.5/3
    b) using secondary sourcesCandidates should appreciate that secondary sources or alternative methods can confirm reproducibility.5/3
    c) identifying extra evidence that is required for a conclusion to be madeCandidates should be able to suggest that extra evidence might be required for a conclusion to be made, and be able to describe the extra evidence required.5/4
    d) evaluating methods of data collection.Candidates should appreciate that the evidence obtained may not allow the conclusion to be made with confidence. Candidates should be able to explain why the evidence obtained does not allow the conclusion to be made with confidence.5/4

    FAS4.6 Use of scientific models and evidence to develop hypotheses, arguments and explanations

    Candidates should be able to:

    FAS4.6.1 review hypotheses in the light of outcomes, by:Additional guidance:AF/thread
    a) considering whether or not any hypothesis made is supported by the evidenceCandidates should be able to assess the extent to which the hypothesis is supported by the outcome.1/2
    b) developing scientific ideas as a result of observations and measurements.Candidates should be able to suggest ways in which the hypothesis may need to be amended, or whether it needs to be discarded in the light of the achieved outcome of an investigation.1/2

    Guidance on Managing Controlled Assessment

    What is Controlled Assessment? 

    For each subject, Controlled Assessment regulations from Ofqual stipulate the level of control required for task setting, task taking and task marking. The 'task' is what the candidate has to do; the 'level of control' indicates the degree of freedom given to teachers and candidates for different aspects of the 'task'.

    For GCSE Further Additional Science, the regulations state:For this specification, this means:
    Task setting – high control■ We prepare equivalent Investigative Skills Assignments (ISAs) each year.
    Task taking  (research/data collection) – limited control■ We require the practical work and data collectionto be carried out under teacher supervision, during normal class contact time.
    ■ If more than one lesson is used, candidates' data and research work must be collected at the end of each lesson.
    ■ Candidates can work together during the investigation, but each candidate must contribute to the collection of the data and process the data individually
    Task taking (analysis and evaluation of findings) – high control■ ISA tests should be taken under formal supervision, in silence, without cooperation between candidates.
    ■ Candidates should be given their processed data for reference during the ISA test, and will also be provided with a data sheet of secondary data.
    ■ Teachers should not help candidates answer the questions.
    ■ Each ISA test has a fixed time limit unless the candidate is entitled to access arrangements.
    ■ Candidates' processed data and their ISA tests are collected by the teacher at the end of each test.
    Task marking – medium control■ We provide 'marking guidelines' for each ISA test.
    ■ We moderate your marking.

    What is the Controlled Assessment like? 

    The Controlled Assessment comprises an ISA test which is assessed in two sections. 

    Prior to taking Section 1 of the ISA test, candidates independently develop their own hypothesis and research possible methods for carrying out an experiment to test their hypothesis. During this research, candidates need to do a risk assessment and prepare a table for their results. 

    Section 1 of the ISA test (45 minutes, 20 marks) consists of questions relating to the candidate's own research. 

    Following Section 1 candidates carry out their investigation, and record and analyse their results. 

    If the candidate's plan is unworkable, unsafe or unmanageable in the laboratory then they may be provided with a method – an example of which will be provided by AQA. For plans that are otherwise good, but unworkable for a good reason (ie logistical) candidates should not lose any marks. However, where the plan is dangerous or unworkable (from a scientific perspective) this will be reflected in the marking. 

    Section 2 of the ISA test (50 minutes, 30 marks) consists of questions related to the experiment candidates have carried out. They are also provided with a data sheet of secondary data by AQA, from which they select appropriate data to analyse and compare with their hypothesis. 

    Candidates will be asked to suggest how ideas from their investigation and research could be used within a new context. 

     Using ISAs 

    The documents provided by AQA for each ISA are: 

    ■ a set of Teachers' Notes 

    ■ the ISA – Section 1 and Section 2 which are to be copied for each candidate 

    ■ the marking guidelines for the teacher to use. 

    The Teachers' Notes provide suggestions on how to incorporate ISAs into the scheme of work. About five lessons should be allowed for the ISA: one lesson for discussion, research and planning; one lesson for the completion of Section 1; one or two lessons for completing the experiment and processing their results and one lesson for completing Section 2 of the ISA. 

    Candidates will be expected to plan their investigation independently and should each draw up an appropriate table for recording their results.

    While carrying out the investigation, candidates should make and record observations. They should make measurements with precision and accuracy. They should record data as it is obtained in a table. They should use ICT where appropriate. Candidates are also required to process the data into a graph or chart. 

    Candidates' tables of data and graphs or charts must be collected by the teacher at the end of each lesson. Candidates must not be allowed to work on the presentation or processing of their data between lessons, because marks are available for these skills. 

    The paper containing Section 2 of the ISA should be taken as soon as possible after completion of the investigation. 

    During the test, candidates should work on their own and in silence. When candidates have completed the test the scripts must be collected. Teachers are required to mark the tests, using the marking guidelines provided by AQA. Tests should be marked in red ink with subtotals placed in the margin. 

    Teachers are expected to use their professional judgement in applying the marking guidelines: for example, applying it sensibly where candidates have given unexpected answers. When teachers have marked the scripts, they may tell candidates their marks but they must not return the scripts. Completed ISAs must be kept under secure conditions while the ISA is valid. 

    Other guidance 

    Teachers' Notes will be put on to the AQA website prior to the ISAs becoming valid. ISA tests and marking guidelines will be published in advance. 

    If ISAs are to be used with different classes, centres must ensure security between sessions. 

    ISAs have specific submission dates. They may not be submitted in more than one year. The submission dates are stated on the front cover of each ISA. 

    Candidates may attempt any number of the ISAs supplied by AQA for a particular subject. The best mark they achieve from a complete ISA is submitted. 

    A candidate is only allowed to have one attempt at each ISA, and this may only be submitted for moderation on one occasion. It would constitute malpractice if the candidate is found to have submitted the same ISA more than once and they could be excluded from at least this qualification. 

    Specimen ISAs or ISAs that are no longer valid may be given to candidates so that they can practise the skills required. In these cases, candidates can be given back their completed and marked scripts. However, ISAs that are currently valid must not be given back to candidates.

    3.7 Mathematical and other requirements

    Mathematical requirements

    Mathematical requirements

    This specification provides learners with the opportunity to develop their skills in communication, mathematics and the use of technology in scientific contexts. In order to deliver the mathematical element of this outcome, assessment materials for this specification contain opportunities for candidates to demonstrate scientific knowledge using appropriate mathematical skills.

    The areas of mathematics that arise naturally from the science content are listed below. This is not a checklist for each question paper, but assessments reflect these mathematical requirements, covering the full range of mathematical skills over a reasonable period of time.

    Candidates are permitted to use calculators in all assessments.

    Candidates are expected to use units appropriately. However, not all questions reward the appropriate use of units.

    All candidates should be able to:

    1. Understand number size and scale and the quantitative relationship between units.

    2. Understand when and how to use estimation.

    3. Carry out calculations involving +, – , x, ÷, either singly or in combination, decimals, fractions, percentages and positive whole number powers.

    4. Provide answers to calculations to an appropriate number of significant figures.

    5 Understand and use the symbols =, <, >, ~.

    6. Understand and use direct proportion and simple ratios.

    7. Calculate arithmetic means.

    8. Understand and use common measures and simple compound measures such as speed.

    9. Plot and draw graphs (line graphs, bar charts, pie charts, scatter graphs, histograms) selecting appropriate scales for the axes.

    10. Substitute numerical values into simple formulae and equations using appropriate units.

    11. Translate information between graphical and numeric form.

    12. Extract and interpret information from charts, graphs and tables.

    13. Understand the idea of probability.

    14. Calculate area, perimeters and volumes of simple shapes.

    In addition, Higher Tier candidates should be able to:

    15. Interpret, order and calculate with numbers written in standard form.

    16. Carry out calculations involving negative powers (only -1 for rate).

    17. Change the subject of an equation.

    18. Understand and use inverse proportion.

    19. Understand and use percentiles and deciles.

    Units, symbols and nomenclature

    Units, symbols and nomenclature used in examination papers will normally conform to the recommendations contained in the following: 

    The Language of Measurement: Terminology used in school science investigations. Association for Science Education (ASE), 2010. ISBN 978 0 86357 424 5. 

    Signs, Symbols and Systematics: The ASE companion to 16–19 Science. Association for Science Education (ASE), 2000. ISBN 978 0 86357 312 5.

    Signs, Symbols and Systematics – the ASE companion to 5–16 Science. Association for Science Education (ASE), 1995. ISBN 0 86357 232 4.

    Equations Sheet

    We will provide an equation sheet for the physics unit.

    Candidates will be expected to select the appropriate equation to answer the question. 

    Data Sheet

    We will provide a data sheet for the chemistry unit. This includes a periodic table and other information.

    Candidates will be expected to select the appropriate information to answer the question.