Revision summary help for the 9-1 AQA GCSE Combined Science Trilogy 1st physics exam paper - learning objectives

AQA GCSE Grade 9-1 Combined Science Trilogy 8464 Physics Paper 1 1F 1H - AQA Grade 9-1 GCSE Combined Science Physics paper 1 Topic 18 "Energy", Topic 19 "Electricity", Topic 20 "Particle model of matter", Topic 21 "Atomic structure"

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LINK for AQA 9-1 GCSE PHYSICS 1 Paper 1

LINK for AQA 9-1 GCSE PHYSICS 2 paper 2

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PLEASE READ CAREFULLY THE FOLLOWING POINTS before using my AQA 9-1 GCSE science pages

  1. ALL my unofficial GCSE (Grade 9-1) revision help summaries are based on the NEW 2016 official AQA (Grade 9-1) GCSE PHYSICS/combined science trilogy physics specifications.

  2. Make sure you know whether you are doing separate science AQA GCSE grade 9-1 PHYSICS OR AQA GCSE grade 9-1 Combined Science Trilogy physics.

  3. Also, make sure you know whether you are entered for a higher tier (HT) or a foundation tier (FT) AQA GCSE science-physics course, so watch out for the (HT only) 'markers'.

  4. I hope my revision pages help as you get to know my website, its very big and not always easy to navigate, but it is no substitute for making good lesson notes, trying your best on homework questions, studying your textbook, doing past papers of AQA GCSE combined science/physics for exam question practice and, above all, attentive to your teacher's teaching!

  5. I know from feedback that my gcse science summary revision pages have proved useful but they do not guarantee a high grade, that all depends on you and the factors mentioned in point 4. above. Please note that my GCSE science revision pages are designed to be used for online convenience, so, beware, printouts could be quite long!
  6. AQA GCSE grade 9-1 Combined Science Trilogy Physics 1 PAST PAPERS and specimen practice paper questions

  7. 'Doc b's chemistry' is a big website so the Google [SEARCH] box at the bottom of each index or revision notes page can be VERY USEFUL - sometimes its better than the indexes for finding things!



Syllabus-specification CONTENT INDEX of revision note summaries

TOPIC revision summaries for AQA GCSE Combined Science Trilogy: Physics Paper 1 (this page)

What's assessed in this paper?    (the 'sub-topic' numbers are just based on a simple numerical order)

SUMMARY Topic 18 Energy   (AQA 9-1 GCSE Combined Science Trilogy Physics paper 1)

Topic 1.1 Energy changes in a system, and the ways energy is stored before and after such changes
Topic 1.2 Conservation and dissipation of energy
Topic 1.3 National and global energy resources

SUMMARY Topic 19 Electricity    (AQA 9-1 GCSE Combined Science Trilogy Physics paper 1)

Topic 2.1 Current, potential difference and resistance
Topic 2.2 Series and parallel circuits
Topic 2.3 Domestic uses and safety
Topic 2.4 Energy transfers

SUMMARY Topic 20 Particle model of matter    (AQA 9-1 GCSE Combined Science Trilogy Physics paper 1)

Topic 3.1 Changes of state and the particle model
Topic 3.2 Internal energy and energy transfers
Topic 3.3 Particle model and pressure

SUMMARY Topic 21 Atomic structure    (AQA 9-1 GCSE Combined Science Trilogy Physics paper 1)

Topic 4.1 Atoms and isotopes
Topic 4.2 Atoms and nuclear radiation


TOPIC revision summaries for AQA GCSE Combined Science Trilogy: Physics 2 (separate page)

What's assessed in this paper?    (the 'sub-topic' numbers are just based on a simple numerical order)

SUMMARY Topic 22 Forces    (AQA 9-1 GCSE Combined Science Trilogy Physics paper 2)

SUMMARY Topic 23 Waves    (AQA 9-1 GCSE Combined Science Trilogy Physics paper 2)

SUMMARY Topic 24 Magnetism and electromagnetism  (AQA 9-1 GCSE Comb. Sci. Trilogy Physics paper 2)


SUBJECT CONTENT of the syllabus-specification:  GCSE Combined Science Trilogy: Physics

TOPICS for  AQA GCSE Combined Science Trilogy: Physics Paper 1


Topic 18 Energy 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

The concept of energy emerged in the 19th century. The idea was used to explain the work output of steam engines and then generalised to understand other heat engines. It also became a key tool for understanding chemical reactions and biological systems.

Limits to the use of fossil fuels and global warming are critical problems for this century. Physicists and engineers are working hard to identify ways to reduce our energy usage.



Topic 1.1 Energy changes in a system, and the ways energy is stored before and after such changes

Topic 1.1.1 Energy stores and systems

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

Know that a system is an object or group of objects. There are changes in the way energy is stored when a system changes.

For example:

an object projected upwards

a moving object hitting an obstacle

an object accelerated by a constant force

a vehicle slowing down

bringing water to a boil in an electric kettle.

Throughout this section on Energy you should be able to :

describe all the changes involved in the way energy is stored when a system changes

and calculate the changes in energy involved when a system is changed by:

heating

work done by forces

work done when charge flows

Be able to use calculations to show on a common scale how the overall energy in a system is redistributed when the system is changed.

 

Topic 1.1.2 Changes in energy

You should be able to calculate the amount of energy associated with a moving object, a stretched spring and an object raised above ground level.

The kinetic energy of a moving object can be calculated using the equation:

kinetic energy = 0.5 × mass × (speed)2,    Ek = 1/2 m v2

kinetic energy, Ek, in joules, J; mass, m, in kilograms, kg; speed, v, in metres per second, m/s

You should be able to recall and apply this equation.

The amount of elastic potential energy stored in a stretched spring can be calculated using the equation:

elastic potential energy = 0.5 × spring constant × (extension)2,    Ee = 1/2 k e2

(assuming the limit of proportionality has not been exceeded)

elastic potential energy, Ee, in joules, J

spring constant, k, in newtons per metre, N/m

extension, e, in metres, m

You should be able to apply this equation which is given on the Physics equation sheet.

The amount of gravitational potential energy gained by an object raised above ground level can be calculated using the equation:

g . p . e . = mass × gravitational field strength × height, Ep = m g h

gravitational potential energy (gpe), Ep, in joules, J

mass, m, in kilograms, kg;

gravitational field strength, g, in newtons per kilogram, N/kg

height, h, in metres, m

(In any calculation the value of the gravitational field strength (g) will be given.)

You should be able to recall and/or apply this equation.

You should have investigated the transfer of energy from a gravitational potential energy store to a kinetic energy store.

 

Topic 1.1.3 Energy changes in systems

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

Know that the amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

change in thermal energy = mass × specific heat capacity × temperature change,  ΔE = m c Δθ

change in thermal energy, ΔE, in joules, J; mass, m, in kilograms, kg;

specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C

temperature change, Δθ, in degrees Celsius, °C

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

You should be able to apply this equation which is given on the Physics equation sheet.

This equation and specific heat capacity are also included in temperature changes in a system and specific heat capacity section.

You should have investigated the specific heat capacity of one or more materials. The investigation involved linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

 

Topic 1.1.4 Power 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

Know that power is defined as the rate at which energy is transferred or the rate at which work is done.

power = energy transferred / time,  P = E / t

power = work done / time,    P = W / t

power, P, in watts, W;    energy transferred, E, in joules, J;

time, t, in seconds, s;    work done, W, in joules, J

An energy transfer of 1 joule per second is equal to a power of 1 watt.

You should be able to give examples that illustrate the definition of power eg comparing two electric motors that both lift the same weight through the same height but one does it faster than the other.

You should be able to recall and apply both equations.


Topic 1.2 Conservation and dissipation of energy

Topic 1.2.1 Energy transfers in a system  

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

You should be able to describe with examples where there are energy transfers in a closed system, that there is no net change to the total energy.

You should be able to describe, with examples, how in all system changes energy is dissipated, so that it is stored in less useful ways. This energy is often described as being ‘wasted’.

You should be able to explain ways of reducing unwanted energy transfers, for example through lubrication and the use of thermal insulation.

The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

You should be able to describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls.

You do not need to know the definition of thermal conductivity.

You should have investigated thermal conductivity using rods of different materials AND the effectiveness of different materials
as thermal insulators and the factors that may affect the thermal insulation properties of a material.

 

Topic 1.2.2 Efficiency

Know that the energy efficiency for any energy transfer can be calculated using the equation:

efficiency = useful output energy transfer / total input energy transfer

Efficiency may also be calculated using the equation:

efficiency = useful power output / total power input

You should be able to recall and apply both equations.

You may be required to calculate or use efficiency values as a decimal or as a percentage (above x 100).

(HT only) You should be able to describe ways to increase the efficiency of an intended energy transfer.


Topic 1.3 National and global energy resources 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 18 "Energy")

Know that the main energy resources available for use on Earth include: fossil fuels (coal, oil and gas), nuclear fuel, bio-fuel, wind, hydroelectricity, geothermal, the tides, the Sun and water waves.

A renewable energy resource is one that is being (or can be) replenished as it is used.

The uses of energy resources include: transport, electricity generation and heating.

You should be able to:

describe the main energy sources available

distinguish between energy resources that are renewable and energy resources that are non-renewable

compare ways that different energy resources are used, the uses to include transport, electricity generation and heating

understand why some energy resources are more reliable than others

describe the environmental impact arising from the use of different energy resources

explain patterns and trends in the use of energy resources.

(Descriptions of how energy resources are used to generate electricity are not required)

consider the environmental issues that may arise from the use of different energy resources

show that science has the ability to identify environmental issues arising from the use of energy resources but not always the power to deal with the issues because of political, social, ethical or economic considerations


Topic 19 Electricity

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

Know that electric charge is a fundamental property of matter everywhere. Understanding the difference in the microstructure of conductors, semiconductors and insulators makes it possible to design components and build electric circuits. Many circuits are powered with mains electricity, but portable electrical devices must use batteries of some kind.

Electrical power fills the modern world with artificial light and sound, information and entertainment, remote sensing and control. The fundamentals of electromagnetism were worked out by scientists of the 19th century. However, power stations, like all machines, have a limited lifetime. If we all continue to demand more electricity this means building new power stations in every generation – but what mix of power stations can promise a sustainable future?



Topic 2.1 Current, potential difference and resistance

Topic 2.1.1 Standard circuit diagram symbols 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

Circuit diagrams use standard symbols.

You should be able to draw and interpret circuit diagrams using the symbols below.

 

Topic 2.1.2 Electrical charge and current

For electrical charge to flow through a closed circuit the circuit must include a source of potential difference.  Electric current is a flow of electrical charge. The size of the electric current is the rate of flow of electrical charge. Charge flow, current and time are linked by the equation:

charge flow = current × time,    Q = I t

charge flow, Q, in coulombs, C

current, I, in amperes, A (amp is acceptable for ampere)

time, t, in seconds, s

You should be able to recall and apply this equation.

Know that the current at any point in a single closed loop of a circuit has the same value as the current at any other point in the same closed loop.

 

Topic 2.1.3 Current, resistance and potential difference

Know that the current (I) through a component depends on both the resistance (R) of the component and the potential difference (V) across the component. The greater the resistance of the component the smaller the current for a given potential difference (pd) across the component.

Questions will be set using the term potential difference. You will gain credit for the correct use of either potential difference or voltage. Current, potential difference or resistance can be calculated using the equation:

potential difference = current × resistance,   V = I R

potential difference, V, in volts, V

current, I, in amperes, A (amp is acceptable for ampere)

resistance, R, in ohms, Ω

You should be able to recall and apply this equation.

You should have investigated, using circuit diagrams to set up a circuit, the factors that affect the resistance of an electrical component  ...

(i) resistance of different length of wire at constant temperature

(ii) combinations of resistors in series and parallel.

 

Topic 2.1.4 Resistors

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

You should be able to explain that, for some resistors, the value of R remains constant but that in others it can change as the current changes

Know that the current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes (graph 1 on right).

The resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component and not in a simple linear way.

The resistance of a filament lamp increases as the temperature of the filament increases (graph 2 on right).

The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction (graph 3 on left).

The resistance of a thermistor decreases as the temperature increases. The applications of thermistors in circuits eg a thermostat is required.

The resistance of an LDR decreases as light intensity increases. The application of LDRs in circuits eg switching lights on when it gets dark is required.

You should be able to:

explain the design and use of a circuit to measure the resistance of a component by measuring the current through, and potential difference across, the component

draw an appropriate circuit diagram using correct circuit symbols.

You should be able to use graphs to determine whether circuit components are linear or non-linear and relate the curves produced to the function and properties of the component.

You should have investigated, using circuit diagrams to construct circuits, the V–I characteristics of a filament lamp, a diode and a resistor at constant temperature.

You should have investigated the relationship between the resistance of a thermistor and temperature

You should have investigated the relationship between the resistance of an LDR and light intensity.

Required practical activity 4: using circuit diagrams to construct appropriate circuits to investigate the I–V characteristics of a variety of circuit elements, including a filament lamp, a diode and a resistor at constant temperature.

 


Topic 2.2 Series and parallel circuits 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

Know there are two ways of joining electrical components, in series and in parallel.

Some circuits include both series and parallel parts.

For components connected in series:

there is the same current through each component

the total potential difference of the power supply is shared between the components

the total resistance of two components is the sum of the resistance of each component.

Rtotal = R1 + R2   (resistance, R, in ohms, Ω)

For components connected in parallel:

the potential difference across each component is the same

the total current through the whole circuit is the sum of the currents through the separate components

the total resistance of two resistors is less than the resistance of the smallest individual resistor.

You should be able to:

use circuit diagrams to construct and check series and parallel circuits that include a variety of common circuit components

describe the difference between series and parallel circuits

explain qualitatively why adding resistors in series increases the total resistance whilst adding resistors in parallel decreases the total resistance

explain the design and use of d.c. series circuits for measurement and testing purposes

calculate the currents, potential differences and resistances in d.c. series circuits

solve problems for circuits which include resistors in series using the concept of equivalent resistance.

You are not required to calculate the total resistance of two resistors joined in parallel.


Topic 2.3 Domestic uses and safety

Topic 2.3.1 Direct and alternating potential difference (d.c. and a.c. current supplies)

Mains electricity is an a.c. supply. In the United Kingdom it has a frequency of 50 Hz and is about 230 V.

You should be able to explain the difference between direct and alternating voltage.

 

Topic 2.3.2 Mains electricity 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

Know that most electrical appliances are connected to the mains using three-core cable.

The insulation covering each wire is colour coded for easy identification: live wire – brown neutral wire – blue earth wire – green and yellow stripes.

The live wire carries the alternating potential difference from the supply. The neutral wire completes the circuit. The earth wire is a safety wire to stop the appliance becoming live.

The potential difference between the live wire and earth (0 V) is about 230 V. The neutral wire is at, or close to, earth potential (0 V). The earth wire is at 0 V, it only carries a current if there is a fault.

Our bodies are at earth potential (0 V). Touching the live wire produces a large potential difference across our body. This causes a current to flow through our body, resulting in an electric shock.

You should be able to explain:

that a live wire may be dangerous even when a switch in the mains circuit is open

the dangers of providing any connection between the live wire and earth.


Topic 2.4 Energy transfers  

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 19 "Electricity")

Topic 2.4.1 Power Content

The power of a device is related to the potential difference across it and the current through it by the equation:

power = potential difference × current,    P = V I

power = (current)2 × resistance,   P = I2 R

power, P, in watts, W

potential difference, V, in volts, V

current, I, in amperes, A (amp is acceptable for ampere)

resistance, R, in ohms, Ω

You should be able to recall and apply both equations.

 

Topic 2.4.2 Energy transfers in everyday appliances

Appreciate that everyday electrical appliances are designed to bring about energy transfers.

The amount of energy an appliance transfers depends on how long the appliance is switched on for and the power of the appliance.

You should be able to describe how different domestic appliances transfer energy from batteries or a.c. mains to the kinetic energy of electric motors or the energy of heating devices.

Work is done when charge flows in a circuit.

The amount of energy transferred by electrical work can be calculated using the equation:

energy transferred = power × time,    E = P t

energy transferred = charge flow × potential difference,    E = Q V

energy transferred, E, in joules, J;      power, P, in watts, W;     time, t, in seconds, s

charge flow, Q, in coulombs, C;     potential difference (p.d), V, in volts

You should be able to recall and apply both equations.

You should be able to explain how the power of a circuit device is related to:

the p.d. across it and the current through it

the energy transferred over a given time.

You should be able to describe, with examples, the relationship between the power ratings for domestic electrical appliances and the changes in stored energy when they are in use.

 

Topic 2.4.3 The National Grid

Know that the National Grid is a system of cables and transformers linking power stations to consumers.

Electrical power is transferred from power stations to consumers using the National Grid.

Step-up transformers are used to increase the potential difference from the power station to the transmission cables then step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use.

This is done because, for a given power, increasing the potential difference reduces the current, and hence reduces the energy losses due to heating in the transmission cables. A reduced voltage is safer for domestic electricity supplies.

You should be able to explain why the National Grid system is an efficient way to transfer energy.

The 'National Grid' power supply


Topic 20 Particle model of matter 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 20 "Particle model of matter")

Appreciate that the particle model is widely used to predict the behaviour of solids, liquids and gases and this has many applications in everyday life. It helps us to explain a wide range of observations and engineers use these principles when designing vessels to withstand high pressures and temperatures such as submarines and spacecraft. It also explains why it is difficult to make a good cup of tea high up a mountain!

Particle theory models, internal energy, heat transfer in state changes and latent heat and particle motion in gases (written more from a 'physics' point of view)



Topic 3.1 Changes of state and the particle model

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 20 "Particle model of matter")

Topic 3.1.1 Density of materials

Know that the density of a material is defined by the equation: density = mass / volume,    ρ = m / V

density, ρ, in kilograms per metre cubed, kg/m3;      mass, m, in kilograms, kg;       volume, V, in metres cubed, m3

You should be able to recall and apply this equation

The particle model can be used to explain

the different states of matter

differences in density

You should be able to recall and apply this equation to changes where mass is conserved.

The particle model can be used to explain

the different states of matter

differences in density.

You should be able to recognise/draw simple diagrams to model the difference between solids, liquids and gases.

You should have investigated, using appropriate apparatus, the densities of regular and irregular solid objects and liquids, making and recording appropriate measurements.

Required practical activity 5 was using appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume should be determined from the dimensions of regularly shaped objects, and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers.

The density of materials and the particle model of matter

 

Topic 3.1.2 Changes of state

Know that when substances change state (melt, freeze, boil, evaporate, condense or sublimate), mass is conserved.

Changes of state are physical changes which differ from chemical changes because the change does not produce a new substance and if the change is reversed the substance recovers its original properties.

You should understand why there is no change in the mass of a substance when it changes state.


Topic 3.2 Internal energy and energy transfers

Topic 3.2.1 Internal energy 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 20 "Particle model of matter")

Know that energy is stored inside a system by the particles (atoms and molecules) that make up the system. This is called internal energy.

Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

Heating changes the energy stored within the system by increasing the energy of the particles that make up the system. This either raises the temperature of the system or produces a change of state.

 

Topic 3.2.2 Temperature changes in a system and specific heat capacity

Know that if the temperature of the system increases: The increase in temperature depends on the mass of the substance heated, the type of material and the energy input to the system.

The following equation applies:

change in thermal energy = mass × specific heat capacity × temperature change,   Δ E = m c Δθ

change in thermal energy, ΔE, in joules, J

mass, m, in kilograms, kg

specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C;

 temperature change, Δθ, in degrees Celsius, °C.

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

You should be able to apply this equation, which is given on the Physics equation sheet, to calculate the energy change involved when the temperature of a material changes.

Specific heat capacity: How to determine it, use of data, calculations and thermal energy stores

 

Topic 3.2.3 Changes of heat and specific latent heat

Know that if a change of state happens: The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.

The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.

energy for a change of state = mass × specific latent heat,    E = m L

energy, E, in joules , J; mass, m, in kilograms, kg; specific latent heat, L, in joules per kilogram, J/kg

Specific latent heat of fusion – change of state from solid to liquid

Specific latent heat of vaporisation – change of state from liquid to vapour

You should be able to interpret heating and cooling graphs that include changes of state.

You  should be able to distinguish between specific heat capacity and specific latent heat.

You should be able to apply this equation, which is given on the Physics equation sheet, to calculate the energy change involved in a change of state.

You should have performed an experiment to measure the latent heat of fusion of water.

Particle theory models, internal energy, heat transfer in state changes and latent heat and particle motion in gases (written more from a 'physics' point of view)


Topic 3.3 Particle model and pressure 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 20 "Particle model of matter")

Topic 3.3.1 Particle motion in gases

Know that the molecules of a gas are in constant random motion. The temperature of the gas is related to the average kinetic energy of the molecules. The higher the temperature the greater the average kinetic energy and so the faster the average speed of the molecules. When the molecules collide with the wall of their container they exert a force on the wall. The total force exerted by all of the molecules inside the container on a unit area of the walls is the gas pressure.

Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.

You should be able to

explain how the motion of the molecules in a gas is related to both its temperature and its pressure

explain qualitatively the relation between the temperature of a gas and its pressure at constant volume.

Particle models of gases–liquids–solids, explaining properties, state changes (written more from a 'chemistry' point of view)


Topic 21 Atomic structure 

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 21 "Atomic structure")

Ionising radiation is hazardous but can be most useful. Although radioactivity was discovered over a century ago, it took many nuclear physicists several decades to understand the structure of atoms, nuclear forces and stability. Early researchers suffered from their exposure to ionising radiation. Rules for radiological protection were first introduced in the 1930s and subsequently improved. Today radioactive materials are widely used in medicine, industry, agriculture and electrical power generation.



Topic 4.1 Atoms and isotopes  

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 21 "Atomic structure")

Topic 4.1.1 The structure of an atom

Know that atoms are very small, having a radius of about 1 × 10-10 metres.

The basic structure of an atom is a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.

The radius of a nucleus is less than 1/10 000 of the radius of an atom and most of the mass of an atom is concentrated in the nucleus.

The electrons are arranged at different distances from the nucleus (different energy levels). The electron arrangements may change with the absorption of electromagnetic radiation (move further from the nucleus to a higher energy level) of by the emission of electromagnetic radiation (move closer to the nucleus to a lower energy level).

You should be able to recognise expressions given in standard form.

 

Topic 4.1.2 Mass number, atomic number and isotopes

Know that in an atom the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge. All atoms of a particular element have the same number of protons. The number of protons in an atom of an element is called its atomic number. The total number of protons and neutrons in an atom is called its mass number.

Atoms can be represented as shown in this example eg or

The mass number is the  top left number and the atomic number (proton number) the bottom left number.

Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.

Atoms turn into positive ions if they lose one or more outer electrons.

You should be able to relate differences between isotopes to differences in conventional representations of their identities, charges and masses.

Atomic Structure - nucleus, electrons, isotopes, history etc. (overlaps with chemistry topics)

Multiple choice quiz on  Atomic structure, isotopes & electronic structure of atoms

 

Topic 4.1.3 The development of the model of the atom

Appreciate that new experimental evidence may lead to a scientific model being changed or replaced.

Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.

The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.

The results of Rutherford and Marsden’s alpha scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. Rutherford and Marsden’s alpha scattering experiment led to the plum pudding model being replaced by the nuclear model.

Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations.

Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.

The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an accepted scientific idea.

You should be able to describe:
why the new evidence from the scattering experiment led to a change in the atomic model

the difference between the plum pudding model of the atom and the nuclear model of the atom.

Details of experimental work supporting the Bohr model are not required.

Details of Chadwick’s experimental work are not required.


Topic 4.2 Atoms and nuclear radiation  

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 21 "Atomic structure")

Topic 4.2.1 Radioactive decay and nuclear radiation

Know that some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable. This is a random process called radioactive decay.

Activity is the rate at which a source of unstable nuclei decay.

Activity is measured in becquerel (Bq), 1 becquerel = 1 decay per second

Count-rate is the number of decays recorded each second by a detector (eg Geiger-Muller tube).

1 becquerel = 1 count per second

The nuclear radiation emitted may be:

an alpha particle (α) – this consists of two neutrons and two protons, it is the same as a helium nucleus

a beta particle (β) – a high speed electron ejected from the nucleus as a neutron turns into a proton

a gamma ray (γ) – electromagnetic radiation from the nucleus

a neutron (n).

The properties of alpha particles, beta particles and gamma rays you need to know are their penetration through materials, their range in air and ionising power.

Alpha particles have a range in air of just a few centimetres and are absorbed by a thin sheet of paper. Alpha particles are strongly ionising.

Beta particles have a range in air of a few metres and are completely absorbed by a sheet of aluminium about 5 mm thick. Beta particles are moderately ionising.

Gamma rays travel great distances through the air and pass through most materials but are absorbed by a thick sheet of lead or several metres of concrete. Gamma rays are weakly ionising.

You should be able to apply their knowledge to the uses of radiation and evaluate the best sources of radiation to use in a given situation.

What is Radioactivity? Why does it happen? - How did they find out there were three types of atomic-ionising radiation?

Detection of Radioactivity, measurement, radiation dose units, ionising radiation sources, radioactive materials and sources of  background radiation

Alpha, beta & gamma radiation - properties of 3 types of radioactive emission & symbols - The dangers of radioactive emissions - beware of ionising radiation from radio-isotopes!

 

Topic 4.2.2 Nuclear equations

Know that nuclear equations are used to represent radioactive decay.

These nuclides can also be written as:  219Rn,   215Po,  12C and 14N

The emission of the different types of nuclear radiation may cause a change in the mass and /or the charge of the nucleus.

For example:

Know that alpha decay causes both the mass and charge of the nucleus to decrease (loss of 2 proton and 2 neutrons, atomic number decreases by 2).

Know that beta decay does not cause the mass of the nucleus to change but does cause the charge of the nucleus to increase (a neutron changes to a proton, atomic number increases by 1).

Know that the emission of a gamma ray does not cause the mass or the charge of the nucleus to change.

You are not required to recall these two examples illustrated above.

You should be able to use the names and symbols of common nuclei and particles to write balanced equations that show single alpha (α) and beta (β) decay. This is limited to balancing the atomic numbers and mass numbers.

The identification of daughter elements from such decays is not required.

What actually happens to the nucleus in alpha and beta radioactive decay? nuclear equations!

 

Topic 4.2.3 Half-lives and the random nature of radioactive decay

(revision notes summary for AQA 9-1 GCSE Combined Science Trilogy: Physics Paper 1, Topic 21 "Atomic structure")

Appreciate that radioactive decay is random so it is not possible to predict which individual nucleus will decay next. But, with a large enough number of nuclei, it is possible to predict how many will decay in a certain amount of time.

The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve, or the average time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.

You should be able to explain the concept of half-life and how it is related to the random nature of radioactive decay.

You should be able to determine the half-life of a radioactive isotope from given information.

(HT only) You should be able to calculate the net decline, expressed as a ratio, in a radioactive emission after a given number of half-lives.

 

Topic 4.2.4 Radioactive contamination

Appreciate that radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials. The hazard from contamination is due to the decay of the contaminating atoms. The type of radiation emitted affects the level of hazard.

Irradiation is the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.

You should be able to compare the hazards associated with contamination and irradiation.

Know that suitable precautions must be taken to protect against any hazard the radioactive source used in the process of irradiation may present.

You should understand that it is important for the findings of studies into the effects of radiation on humans to be published and shared with other scientists so that the findings can be checked by peer review.


PAST PAPERS   (Practice exam question papers for revising AQA 9-1 GCSE Combined Science Trilogy Physics Paper 1, Topic 18 "Energy", Topic 19 "Electricity", Topic 20 "Particle model of matter", Topic 21 "Atomic structure")



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