Revision summary help OCR GCSE 21st Century Combined Science B physics exam papers - learning objectives P4-P6

OCR Level 1/2 GCSE (Grade 9-1) in Combined Science B Physics (Twenty First Century Science) (J260) - OCR 21st Century GCSE Combined Science Revision Summaries for physics Chapter P4 "Explaining motion", Chapter P5 "Radioactive materials", Chapter P6 "Matter - models and explanations", Chapter BCP7 "Ideas about science" for physics Paper 03

LINK for OCR 21st Century Combined Science physics chapters P1-P3

LINK for OCR 21st Century 9-1 GCSE PHYSICS B chapters P1-P3

LINK for OCR 21st Century 9-1 GCSE PHYSICS B chapters P4-P6

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  1. ALL my unofficial GCSE (Grade 9-1) revision help summaries are based on the NEW 2016 official OCR 21st Century Science B (Grade 9-1) GCSE PHYSICS/combined science physics specifications.

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In OCR 9-1 GCSE Twenty First Century Science B physics courses, note the following!

Note: Combined Science Paper 04 assesses the contents of ALL the chapters of biology, chemistry and physics!



Syllabus-specification CONTENT INDEX of revision summary notes

 What's assessed in this paper?    (for OCR 9-1 GCSE Twenty First Century Combined Science B physics paper)

Revision SUMMARY Chapter P1: Radiation and waves   (separate page)

Chapter P1.1 What are the risks and benefits of using radiations?

Chapter P1.2 What is climate change and what is the evidence for it?

Chapter P1.3 How do waves behave?

Revision SUMMARY Chapter P2: Sustainable energy    (separate page)

Chapter P2.1 How much energy do we use?

Chapter P2.2 How can electricity be generated?

Revision SUMMARY Chapter P3: Electric circuits  (separate page)

Chapter P3.1 What determines the current in an electric circuit?

Chapter P3.2 How do series and parallel circuits work?

Chapter P3.3 What determines the rate of energy transfer in a circuit?

Chapter P3.4 What are magnetic fields?

Chapter P3.5 How do electric motors work?

Revision SUMMARY Chapter P4: Explaining motion   (this page)

Chapter P4.1 What are forces?

Chapter P4.2 How can we describe motion?

Chapter P4.3 What is the connection between forces and motion?

Chapter P4.4 How do we describe motion in terms of energy transfers?

Revision SUMMARY Chapter P5: Radioactive materials   (this page)

Chapter P5.1 What is radioactivity?

Chapter P5.2 How can radioactive materials be used safely?

Revision SUMMARY Chapter P6: Matter – models and explanations   (this page)

Chapter P6.1 How does energy transform matter?

Chapter P6.2 How does the particle model explain the effects of heating?

Chapter P6.3 How does the particle model relate to material under stress?

Revision SUMMARY Chapter BCP7: Ideas about Science  (this page)

IaS1 What needs to be considered when investigating phenomenon scientifically?

IaS2 What conclusions can we make from data?

IaS3 How are scientific explanations developed?

IaS4 How do science and technology impact society?


Chapter P4: Explaining motion 

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

Note: Combined Science Paper 04 assesses the contents of ALL the chapters of biology, chemistry and physics!



Chapter P4 Explaining motion  

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

Introduction overview

Simple but counterintuitive concepts of forces and motion, developed by Galileo and Newton, can transform your insight into everyday phenomena. These ideas also underpin an enormous range of modern applications, including spacecraft, urban mass transit systems, sports equipment and rides at theme parks.

Topic P4.1 reviews the idea of forces: identifying, describing and using forces to explain simple situations.

Topic P4.2 looks at how speed is measured and represented graphically and introduces the vector quantities of velocity and displacement. The relationships between distance, speed, acceleration and time are an example of simple mathematical modelling that can be used to predict the speed and position of a moving object.

The relationship between forces and motion is developed in Topic P4.3, where resultant forces and changes in momentum are described. These ideas are then applied in the context of road safety.

Topic P4.4 considers how we can describe motion in terms of energy transfers.


What you should have learned and experienced from KS3 science about force and motion ...

describe motion using words and with distance–time graphs

use the relationship average speed = distance ÷ time

identify the forces when two objects in contact interact; pushing, pulling, squashing, friction, turning

use arrows to indicate the different forces acting on objects, and predict the net force when two or more forces act on an object

know that the forces due to gravity, magnetism and electric charge are all non-contact forces

understand how the forces acting on an object can be used to explain its motion.
 


Chapter P4.1 What are forces?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

Force arises from an interaction between two objects, and when two objects interact, both always experience a force and that these two forces form an interaction pair. The two forces in an interaction pair are the same kind of force, equal in size and opposite in direction, and act on different objects (Newton’s third law).

Friction is the interaction between two surfaces that slide (or tend to slide) relative to each other: each surface experiences a force in the direction that prevents (or tends to prevent) relative movement.

There is an interaction between an object and the surface it is resting on: the object pushes down on the surface, the surface pushes up on the object with an equal force, and this is called the normal contact force.

In everyday situations, a downward force acts on every object, due to the gravitational attraction of the Earth. This is called its weight. It can be measured (in N) using a spring (or top-pan) balance. The weight of an object is proportional to its mass. Near the Earth’s surface, the weight of a 1 kg object is roughly 10 N. The Earth’s gravitational field strength is therefore 10 N/kg.

Newton’s insight that linked the force that causes objects to fall to Earth with force that keeps the Moon in orbit around the Earth led to the first universal law of nature.

1. Be able to recall and apply Newton’s Third Law.

Practical work - Investigating the effect of different combinations of surfaces on the frictional forces.

Be able to explaining how Newton’s discovery of the universal nature of gravity is an example of the role of imagination in scientific discovery.

2. Be able to recall examples of ways in which objects interact: by gravity, electrostatics, magnetism and by contact (including normal contact force and friction).

3. Be able to describe how examples of gravitational, electrostatic, magnetic and contact forces involve interactions between pairs of objects which produce a force on each object.

4. Be able to represent interaction forces as vectors.

5. Be able to define weight.

6. Be able to describe how weight is measured.

7. Be able to recall and apply the relationship between the weight of an object, its mass and the gravitational field strength using the formula:

weight (N) = mass (kg) × gravitational field strength


Chapter P4.2 How can we describe motion?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

The motion of a moving object can be described using the speed the object is moving, the direction it is travelling and whether the speed is changing.

The distance an object has travelled at a given moment is measured along the path it has taken.

The displacement of an object at a given moment is its net distance from its starting point together with an indication of direction.

The velocity of an object at a given moment is its speed at that moment, together with an indication of its direction.

Distance and speed are scalar quantities; they give no indication of direction of motion.

Displacement and velocity are vector quantities, and include information about the direction.

In everyday situations, acceleration is used to mean the change in speed of an object in a given time interval.

Distance–time graphs and speed-time graphs can be used to describe motion. The average speed can be calculated from the slope of a distance–time graph.

The average acceleration of an object moving in a straight line can be calculated from a speed-time graph. The distance travelled can be calculated from the area under the line on a speed-time graph.

The mathematical relationships between acceleration, speed, distance, and time are a simple example of a computational model. The model can be used to predict the speed and position of an object moving at constant speed or with constant acceleration.

1. Be able to recall and apply the relationship: average speed (m/s) = distance (m) ÷ time (s)

Practical work:

Using a variety of methods to measure distances, speeds and times and to calculate acceleration.

Comparing methods of measuring the acceleration due to gravity.

Using mathematical and computational models to make predictions about the motion of moving objects.

Exploring using simple computer models to predict motion of a moving object.

2. Be able to recall typical speeds encountered in everyday experience for wind, and sound, and for walking, running, cycling and other transportation systems.

3. (a) Be able to make measurements of distances and times, and calculate speeds.

3. (b) Be able to describe how to use appropriate apparatus and techniques to investigate the speed of a trolley down a ramp.

4. make calculations using ratios and proportional reasoning to convert units, to include between m/s and km/h.

5. Be able to explain the vector-scalar distinction as it applies to displacement and distance, velocity and speed.

6. (a) Be able to recall and apply the relationship:

acceleration (m/s2) = change in speed (m/s) ÷ time taken (s)

6. (b) Be able to explain how to use appropriate apparatus and techniques to investigate acceleration

7. Be able to select and apply the relationship:

(final speed (m/s))2 - (initial speed(m/s))2 = 2 x acceleration (m/s2) x distance (m)

8. Be able to draw and use graphs of distances and speeds against time to determine the speeds and accelerations involved.

9. Be able to interpret distance-time and velocity-time graphs, including relating the lines, slopes and enclosed areas in such graphs to the motion represented.

10. Be able to interpret enclosed areas in velocity – time graphs.

11. Be able to recall the value of acceleration in free fall and calculate the magnitudes of everyday accelerations using suitable estimates of speeds and times.


Chapter P4.3 What is the connection between forces and motion?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

When forces act on an object the resultant force is the sum of all the individual forces acting on it, taking their directions into account.

(HT only)  If a resultant force acts on an object, it causes a change of momentum in the direction of the force. The size of the change of momentum of an object is proportional to the size of the resultant force acting on the object and to the time for which it acts (Newton’s second law).

For an object moving in a straight line:

(a) if the resultant force is zero, the object will move at constant speed in a straight line (Newton’s first law).

(b) if the resultant force is in the direction of the motion, the object will speed up (accelerate).

(c) if the resultant force is in the opposite direction to the motion, the object will slow down.

(HT only) In situations involving a change in momentum (such as a collision), the longer the duration of the impact, the smaller the average force for a given change in momentum.

In situations where the resultant force on a moving object is not in the line of motion, the force will cause a change in direction.

1. Be able to describe examples of the forces acting on an isolated solid object or system.

Practical work

Investigating factors that might affect human reaction times.

Investigating the use of crumple zones to reduce the stopping forces.

2. Be able to describe, using free body diagrams, examples where several forces lead to a resultant force on an object and the special case of balanced forces (equilibrium) when the resultant force is zero (qualitative only).

3. (HT only) Be able to use scale drawings of vector diagrams to illustrate the addition of two or more forces, in situations when there is a net force, or equilibrium (limited to parallel and perpendicular vectors only).

4. (HT only) Be able to recall and apply the equation for momentum and describe examples of the conservation of momentum in collisions:

momentum (kg m/s) = mass (kg) x velocity (m/s)

5. (HT only) Be able to select and apply Newton's second law in calculations relating force, change in momentum and time:

change of momentum (kg m/s) = resultant force (N) × time for which it acts (s)

(HT only) If the force is perpendicular to the direction of motion the object will move in a circle at a constant speed – the speed doesn’t change but the velocity does. For example, a planet in orbit around the Sun – gravity acts along the radius of the orbit, at right angles to the planet’s path.

6. Be able to apply Newton’s first law to explain the motion of objects moving with uniform velocity and also the motion of objects where the speed and/or direction changes.

7. (HT only) Be able to explain with examples that motion in a circular orbit involves constant speed but changing velocity qualitative only (qualitative only, no calculations to do!).

The mass of an object can be thought of as the amount of matter in an object – the sum of all the atoms that make it up. Mass is measured in kilograms.

(HT only) The mass of an object is also a measure of its resistance to any change in its motion (its inertia); using this definition the inertial mass is the ratio of the force applied to the resulting acceleration.

Newton wrote about how the length of time a force acted on an object would change the object’s ‘amount of motion’ , and the way he used the term makes it clear that he is describing what we now call momentum, this has led to Newton’s second law being expressed in two ways – in terms of change in momentum (HT only), and in terms of acceleration.

Newton’s explanation of motion is one of the great intellectual leaps of humanity. It is a good example of the need for creativity and imagination to develop a scientific explanation of something that had been observed and discussed for many years.

8. (HT only) Be able to explain that inertial mass is a measure of how difficult it is to change the velocity of an object and that it is defined as the ratio of force over acceleration.

9. Be able to recall and apply the equation of Newton's 2nd law relating force, mass and acceleration:

force (N) = mass (kg) × acceleration (m/s2)

Be able to explaining why Newton’s explanation of motion is an example of the need for creative thinking in developing new scientific explanations.

Ideas about force and momentum (HT only) can be used to explain road safety measures, such as stopping distances, car seatbelts, crumple zones, air bags, and cycle and motorcycle helmets.

Improvements in technology based on Newton’s laws of motion (together with the development of new materials) have made all forms of travel much safer.

10. Be able to use and apply equations relating force, mass, velocity, acceleration, and momentum (HT only) to explain relationships between the quantities.

11. Be able to explain methods of measuring human reaction times and recall typical results.

Be able to describe and explain examples of how application of Newton’s laws of motion have led developments in road safety.

Discuss people’s willingness to accept risk in the context of car safety and explain ways in which the risks can be reduced.

12. Be able to explain the factors which affect the distance required for road transport vehicles to come to rest in emergencies and the implications for safety.

13. Be able to explain the dangers caused by large decelerations.


Chapter P4.4 How can we describe motion in terms of energy transfers?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P4 "Explaining motion")

Energy is always conserved in any event or process. Energy calculations can be used to find out if something is possible and what will happen, but not explain why it happens.

The store of energy of a moving object is called its kinetic energy.

As an object is raised, its store of gravitational potential energy increases, and as it falls, its gravitational potential energy decreases.

When a force moves an object, it does work on the object, energy is transferred to the object; when work is done by an object, energy is transferred from the object to something else, for example:

when an object is lifted to a higher position above the ground, work is done by the lifting force; this increases the store of gravitational potential energy.

when a force acting on an object makes its velocity increase, the force does work on the object and this results in an increase in its store of kinetic energy.

 If friction and air resistance can be ignored, an object’s store of kinetic energy changes by an amount equal to the work done on it by an applied force; in practice air resistance or friction will cause the gain in kinetic energy to be less than the work done on it by an applied force in the direction of motion, because some energy is dissipated through heating.

Calculating the work done when climbing stairs or lifting a load, and the power output, makes a link back to the usefulness of electrical appliances for doing many everyday tasks.

1. Be able to describe the energy transfers involved when a system is changed by work done by forces including

(a) to raise an object above ground level

(b) to move an object along the line of action of the force

Practical work

Using datalogging software to calculate the efficiency of energy transfers when work is done on a moving object.

Measuring the work done by an electric motor lifting a load, and calculate the efficiency.

2. Be able to recall and apply the relationship to calculate the work done (energy transferred) by a force:

work done (Nm or J) = force (N) x distance (m) (along the line of action of the force)

3. Be able to recall the equation and calculate the amount of energy associated with a moving object:

kinetic energy (J) = 0.5 x mass (kg) x (speed (m/s))2       KE = 1/2mv2

4. Be able to recall the equation and calculate the amount of energy associated with an object raised above ground level.

gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)       GPE = mgh

5. Be able to make calculations of the energy transfers associated with changes in a system, recalling relevant equations for mechanical processes.

6. Be able to calculate relevant values of stored energy and energy transfers; convert between newton-metres and joules.

7. Be able to describe all the changes involved in the way energy is stored when a system changes, for common situations: including an object projected upwards or up a slope, a moving object hitting an obstacle, an object being accelerated by a constant force, a vehicle slowing down.

8. Be able to explain, with reference to examples, the definition of power as the rate at which energy is transferred (work done) in a system.

9. Be able to recall and apply the relationship: power (W) = energy transferred (J) / time (s)


Chapter P5: Radioactive materials

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P5 "Radioactive materials")



Chapter P5 Radioactive materials  

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P5 "Radioactive materials")

Introduction overview

The terms ‘radiation’ and ‘radioactivity’ are often interchangeable in the public mind. Because of its invisibility, radiation is commonly feared. A more objective evaluation of risks and benefits is encouraged through developing an understanding of the many practical uses of radioactive materials.

In Topic P5.1 you study the evidence of a nuclear model of the atom, including Rutherford’s alpha particle scattering experiment. It then uses the nuclear model to explain what happens during radioactive decay. The properties of alpha, beta and
gamma radiation are investigated and ideas about half-life are developed.

In Topic P5.2 learners learn about the penetration properties of ionising radiation which leads to a consideration of the use of radioactive materials in the health sector, and how they can be handled safely. In the context of health risks associated with irradiation and/or contamination by radioactive material, they also learn about the interpretation of data on risk.


What you should have learned and experienced from KS3 science about ? ...

recall that in each atom its electrons are arranged at different distances from the nucleus

recall that gamma rays are emitted from the nuclei of atoms

be able to describe how ionising radiation can have hazardous effects, notably on human bodily tissues.


P5.1 What is radioactivity?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P5 "Radioactive materials")

An atom has a nucleus, made of protons and neutrons, which is surrounded by electrons.

The modern model of the atom developed over time as scientists rejected earlier models and proposed new ones to fit the currently available evidence.

Each stage relied on scientists using reasoning to propose models which fitted the evidence available at the time. Models were rejected, modified and extended as new evidence became available (IaS3).

After the discovery of the electron in the 19th century by Thomson scientists imagined that atoms were small particles of positive matter with the negative electrons spread through, like currants in a cake.

This was the model used until 1910 when the results of the Rutherford-Geiger-Marsden alpha particle scattering experiment provided evidence that a gold atom contains a small, massive, positive region (the nucleus).

Atoms are small – about 10–10 m across, and the nucleus is at the centre, about a hundred-thousandth of the diameter of the atom.

Each atom has a nucleus at its centre and that nucleus is made of protons and neutrons. For an element, the number of the protons is always the same but the number of neutrons may differ. Forms of the same element with different numbers of neutrons are called the isotopes of the element.

Interpreting the unexpected results of the Rutherford Geiger-Marsden experiment required imagination to consider a new model of the atom.

Some substances emit ionising radiation all the time and are called radioactive. The ionising radiation (alpha, beta, gamma, and neutron) is emitted from the unstable nucleus of the radioactive atoms, which as a result become more stable.

Alpha particles consist of two protons and two neutrons, and beta particles are identical to electrons. Gamma radiation is very high frequency electromagnetic radiation.

Radioactive decay is a random process. For each radioactive isotope there is a different constant chance that any nucleus will decay. Over time the activity of radioactive sources decreases, as the number of undecayed nuclei decreases.

The time taken for the activity to fall to half is called the half-life of the isotope and can be used to calculate the time it takes for a radioactive material to become relatively safe.

1. Be able to describe the atom as a positively charged nucleus surrounded by negatively charged electrons, with the nuclear radius much smaller than that of the atom and with almost all of the mass in the nucleus.

How has our understanding of the structure of atoms developed over time? (C2.1)

Be able to explaining how the development of the nuclear model of the atom is an example of how scientific explanations become accepted.

Practical work

Collecting data to calculate the half-life of a radioactive isotope.

Using a random event such as dice-throwing to model

2. Be able to describe how and why the atomic model has changed over time to include the main ideas of Dalton, Thomson, Rutherford and Bohr.

3. Be able to recall the typical size (order of magnitude) of atoms and small molecules.

4. Be able to recall that atomic nuclei are composed of both protons and neutrons, and that the nucleus of each element has a characteristic positive charge.

5. Be able to recall that nuclei of the same element can differ in nuclear mass by having different numbers of neutrons, these are called isotopes.

6. Be able to use the conventional representation to show the differences between isotopes, including their identity, charge and mass.

7. Be able to recall that some nuclei are unstable and may emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma rays.

8. Be able to relate emissions of alpha particles, beta particles, or neutrons, and gamma rays to possible changes in the mass or the charge of the nucleus, or both.

9. Be able to use names and symbols of common nuclei and particles to write balanced equations that represent the emission of alpha, beta, gamma, and neutron radiations during radioactive decay.

10. Be able to explain the concept of half-life and how this is related to the random nature of radioactive decay.

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

12. Be able to interpret activity-time graphs to find the half-life of radioactive materials.


Chapter P5.2: How can radioactive materials be used safely?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P5 "Radioactive materials")

Ionising radiation can damage living cells and these may be killed or may become cancerous, so radioactive materials must be handled with care. In particular, a radioactive material taken into the body (contamination) poses a higher risk than the same material outside as the material will continue to emit ionising radiation until it leaves the body.

Whilst ionising radiation can cause cancer, it can also be used for imaging inside the body and to kill cancerous cells.

Doctors and patients need to consider the risks and benefits when using ionising radiation to treat diseases.

1. Be able to recall the differences in the penetration properties of alpha particles, beta particles and gamma rays.

What are the risks and benefits of using electromagnetic radiations? (P1.2)

Practical work - Collect and interpret data to show the penetration properties of ionising radiations.

Discuss ideas about correlation and cause in the context of links between ionising radiation and cancer.

Discuss the uses of ionising radiation, with reference to its risks and benefits.

2. Be able to recall the differences between contamination and irradiation effects and compare the hazards associated with each of these.

3. Be able to describe the different uses of nuclear radiations for exploration of internal organs, and for control or destruction of unwanted tissue.

4. Be able to explain how ionising radiation can have hazardous effects, notably on human bodily tissues.

5. Be able to explain why the hazards associated with radioactive material differ according to the radiation emitted and the half-life involved.


Chapter P6: Matter - models and explanations

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P6 "Matter - models and explanations")



Chapter P6 Matter – models and explanations

Introduction overview

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P6 "Matter - models and explanations")

The famous quantum physicist Richard Feynman said: “If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms— little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.”

In chapter P6 the particle model described by Feynman is used to predict and explain some properties of matter.

Topic P6.1 explores the relationship between energy and temperature and the ways in which energy transfer transforms matter.

Topic P6.2 considers how the particle model explains the differences in densities between solids, liquids and gases and the effect of heating both in terms of temperature changes and changes of state.

Topic P6.3 considers the behaviour of materials under stress and how the particle model can explain differences in behaviour.


What you should have learned and experienced from KS3 science about matter and particles ...

be able to use a particulate model of matter to explain states of matter and changes of state

have investigated stretching and compressing materials and identifying those that obey Hooke’s law

be able to describe how the extension or compression of an elastic material changes as a force is applied, and make a link between the work done and energy transfer during compression or extension

have investigated pressure in liquids and related this to floating and sinking

be able to relate atmospheric pressure to the weight of air overhead.


Chapter P6.1 How does energy transform matter?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P6 "Matter - models and explanations")

It took the insight of a number of eighteenth and nineteenth century scientists to appreciate that heat and work were two aspects of the same quantity, which we call energy. Careful experiments devised by Joule showed that equal amounts of mechanical work would always produce the same temperature rise.

Energy can be supplied to raise the temperature of a substance by heating using a fuel, or an electric heater, or by doing work on the material.

 Mass – the amount of matter in an object – depends on its volume and the density of the material of which it consists.

The temperature rise of an object when it is heated depends on its mass and the amount of energy supplied. Different substances store different amounts of energy per kilogram for each °C temperature rise – this is called the specific heat capacity of the material.

When a substance in the solid state is heated its temperature rises until it reaches the melting point of the substance, but energy must continue to be supplied for the solid to melt. Its temperature does not change while it melts, and the change in density on melting is very small. Similarly as a substance in the liquid state is heated its temperature rises until it reaches boiling point; its temperature does not change, although energy continues to be supplied while it boils. The change in density on boiling is very great; a small volume of liquid produces a large volume of vapour.

Different substances require different amounts of energy per kilogram to change the state of the substance – this is called the specific latent heat of the substance.

1. (a) Be able to define density

1. (b) Be able to describe how to determine the densities of solid and liquid objects using measurements of length, mass and volume.

Links: How much energy do we use? (P2.1)

What determines the rate of energy transfer in a circuit? (P3.4)

How can we describe motion in terms of energy transfers? (P4.4).

Practical work

Devising a method to measure the density of irregular objects.

Measuring the specific heat capacity of a range of substances such as water, copper, aluminium.

Measuring the latent heat of fusion of a substance in the solid state and the latent heat of vaporisation of a substance in the liquid state.

2. Be able to recall and apply the relationship between density, mass and volume to changes where mass is conserved:

density (kg/m3) = mass (kg) ÷ volume (m3)

3. Be able to describe the energy transfers involved when a system is changed by heating (in terms of temperature change and specific heat capacity).

4. Be able to define the term specific heat capacity and distinguish between it and the term specific latent heat.

5. (a) Be able to select and apply the relationship between change in internal energy of a material and its mass, specific heat capacity and temperature:

change in internal energy (J) = mass (kg) x specific heat capacity (J /kg / °C) x change in temperature (°C)

5. (b) Be able to explain how to safely use apparatus to determine the specific heat capacity of materials.

Show that the same amount of work always results in the same temperature rise.

Collecting data, plot and interpret graphs that show how the temperature of a substance changes when heated by a constant supply of energy.

The density change on boiling is very great; a small volume of liquid produces a large volume of vapour.

Different substances require different amounts of energy per kilogram to change the state of the substance – this is called the specific latent heat of the substance.

6. Be able to select and apply the relationship between energy needed to cause a change in state, specific latent heat and mass:

energy to cause a change of state (J) = mass (kg) x specific latent heat (J/kg)

7. Be able to describe all the changes involved in the way energy is stored when a system changes, and the temperature rises, for example: a moving object hitting an obstacle, an object slowing down, water brought to a boil in an electric kettle.

8. Be able to make calculations of the energy transfers associated with changes in a system when the temperature changes, recalling or selecting the relevant equations for mechanical, electrical, and thermal processes.


Chapter P6.2 How does the particle model explain the effects of heating?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P6 "Matter - models and explanations")

The particle model of matter describes the arrangements and behaviours of particles (atoms and molecules); it can be used to predict and explain the differences in properties between solids, liquids and gases. In this model:

All matter is made of very tiny particles.

There is no other matter except these particles (in particular, no matter between them).

Particles of any given substance are all the same.

Particles of different substances have different masses.

There are attractive forces between particles. These differ in strength from one substance to another.

In the solid state, the particles are close together and unable to move away from their neighbours.

In the liquid state, the particles are also close together, but can slide past each other.

In the gas state, the particles are further apart, and can move freely.

The particle model is an example of how scientists use models as tools for explaining observed phenomena.

The particle model can be used to describe and predict physical changes when matter is heated.

The particles are always moving: in the solid state, they are vibrating; in the liquid state, they are vibrating and jostling around; in the gas state, they are moving freely in random directions.

A substance in the gas state exerts pressure on its container because the momentum of the particles changes when they collide with walls of the container.

The hotter something is, the higher its temperature is and the faster its particles are vibrating or moving.

Careful experimentation and mathematical analysis showed that the temperature of a substance was linked to the kinetic energy of its atoms or molecules.
.

1. Be able to explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules.

Using the particle model to explain familiar or unfamiliar phenomena and make predictions.

2. Be able to use the particle model of matter to describe how mass is conserved, when substances melt, freeze, evaporate, condense or sublimate and the material recovers its original properties if the change is reversed

3. Be able to use the particle model to describe how heating a system will change the energy stored within the system and raise its temperature or produce changes of state.

4. Be able to explain how the motion of the molecules in a gas is related both to its temperature and its pressure: hence explain the relation between the temperature of a gas and its pressure at constant volume (qualitative only, no calculations to do)


P6.3 How does the particle model relate to material under stress?

 (Revision for OCR GCSE 9–1 Twenty First Century Science Combined Science B physics paper 03, Topics for Chapter P6 "Matter - models and explanations")

When more than one force is applied to a solid material it may be compressed, stretched or twisted. When the forces are removed it may return to its original shape or become permanently deformed.

These effects can be explained using ideas about particles in the solid state. A substance in the solid state is a fixed shape due to the forces between the particles.

Compressing or stretching the material changes the separation of the particles, and the forces between the particles.

Elastic materials spring back to their original shape. If the forces are too large the material becomes plastic and is permanently distorted.

For some materials, the extension is proportional to the applied force, but in other systems, such as rubber bands the relationship is not linear, even though they are elastic.

When work is done by a force to compress or stretch an spring or other simple system, energy is stored, this energy can be recovered when the force is removed.

1. Be able to explain, with examples, that to stretch, bend or compress an object, more than one force has to be applied.

Practical work - Investigating the force-extension properties of a variety of materials, identifying those that obey Hooke’s law, those that behave elastically, and those that show plastic deformation.

2. Be able to describe and (HT only) use the particle model to explain the difference between elastic and plastic deformation caused by stretching forces.

3. (a) Be able to describe the relationship between force and extension for a spring and other simple systems.

3. (b) Be able to describe how to measure and observe the effect of forces on the extension of a spring.

4. Be able to describe the difference between the force-extension relationship for linear systems and for non-linear systems.

5. Be able to recall and apply the relationship between force, extension and spring constant for systems where the force-extension relationship is linear:

force exerted by a spring (N) = extension (m) × spring constant (N/m)

6. (a) Be able to calculate the work done in stretching a spring or other simple system, by calculating the appropriate area on the force-extension graph.

6. (b) Be able to describe how to safely use apparatus to determine the work done in stretching a spring.

7. Be able to select and apply the relationship between energy stored, spring constant and extension for a linear system:

energy stored in a stretched spring (J) = ½ × spring constant (N/m) × (extension (m))2


Chapter BCP7: Ideas about Science   (For OCR GCSE (9–1) Twenty First Century Combined Science B physics exam papers)



Chapter IaS1 What needs to be considered when investigating a phenomenon scientifically?

The aim of science is to develop good explanations for natural phenomena. There is no single ‘scientific method’ that leads to good explanations, but scientists do have characteristic ways of working. In particular, scientific explanations are based on a cycle of collecting and analysing data.

Usually, developing an explanation begins with proposing a hypothesis. A hypothesis is a tentative explanation for an observed phenomenon (“this happens because…”).

The hypothesis is used to make a prediction about how, in a particular experimental context, a change in a factor will affect the outcome. A prediction can be presented in a variety of ways, for example in words or as a sketch graph.

In order to test a prediction, and the hypothesis upon which it is based, it is necessary to plan an experimental strategy that enables data to be collected in a safe, accurate and repeatable way.

1. in given contexts use scientific theories and tentative explanations to develop and justify hypotheses and predictions

2. suggest appropriate apparatus, materials and techniques, justifying the choice with reference to the precision, accuracy and validity of the data that will be collected

3. recognise the importance of scientific quantities and understand how they are determined

4. identify factors that need to be controlled, and the ways in which they could be controlled

5. suggest an appropriate sample size and/or range of values to be measured and justify the suggestion

6. plan experiments or devise procedures by constructing clear and logically sequenced strategies to: make observations, produce or characterise a substance, test hypotheses, collect and check data and explore phenomena.

7. identify hazards associated with the data collection and suggest ways of minimizing the risk

8. use appropriate scientific vocabulary, terminology and definitions to communicate the rationale for an investigation and the methods used using diagrammatic, graphical, numerical and symbolic forms


Chapter IaS2 What conclusions can we make from data?

The cycle of collecting, presenting and analysing data usually involves translating data from one form to another, mathematical processing, graphical display and analysis; only then can we begin to draw conclusions.

A set of repeat measurements can be processed to calculate a range within which the true value probably lies and to give a best estimate of the value (mean).

Displaying data graphically can help to show trends or patterns, and to assess the spread of repeated measurements.

Mathematical comparisons between results and statistical methods can help with further analysis.

1. present observations and other data using appropriate formats

P6.2 (mechanical equivalent of heat)

Be able to describe and explain how careful experimental strategy can yield high quality data.

2. when processing data use SI units where appropriate (e.g. kg, g, mg; km, m, mm; kJ, J) and IUPAC chemical nomenclature unless inappropriate

3. when processing data use prefixes (e.g. tera, giga, mega, kilo, centi, milli, micro and nano) and powers of ten for orders of magnitude

4. be able to translate data from one form to another

5. when processing data interconvert units

6. when processing data use an appropriate number of significant figures

7. when displaying data graphically select an appropriate graphical form, use appropriate axes and scales, plot data points correctly, draw an appropriate line of best fit, and indicate uncertainty (e.g. range bars)

8. when analysing data identify patterns/trends, use statistics (range and mean) and obtain values from a line on a graph (including gradient, interpolation and extrapolation)

Data obtained must be evaluated critically before we can make conclusions based on the results. There could be many reasons why the quality (accuracy, precision, repeatability and reproducibility) of the data could be questioned, and a number of ways in which they could be improved.

Data can never be relied on completely because observations may be incorrect and all measurements are subject to uncertainty (arising from the limitations of the measuring equipment and the person using it). A result that appears to be an outlier should be treated as data, unless there is a reason to reject it (e.g. measurement or recording error).

9. in a given context evaluate data in terms of accuracy, precision, repeatability and reproducibility, identify potential sources of random and systematic error, and discuss the decision to discard or retain an outlier

10. evaluate an experimental strategy, suggest improvements and explain why they would increase the quality (accuracy, precision, repeatability and reproducibility) of the data collected, and suggest further investigations

Agreement between the collected data and the original prediction increases confidence in the tentative explanation (hypothesis) upon which the prediction is based, but does not prove that the explanation is correct. Disagreement between the data and the prediction indicates that one or other is wrong, and decreases our confidence in the explanation.

11. in a given context interpret observations and other data (presented in diagrammatic, graphical, symbolic or numerical form) to make inferences and to draw reasoned conclusions, using appropriate scientific vocabulary and terminology to communicate the scientific rationale for findings and conclusions

12. explain the extent to which data increase or decrease confidence in a prediction or hypothesis


Chapter IaS3 How are scientific explanations developed?

Scientists often look for patterns in data as a means of identifying correlations that can suggest cause-effect links – for which an explanation might then be sought.

The first step is to identify a correlation between a factor and an outcome. The factor may then be the cause, or one of the causes, of the outcome. In many situations, a factor may not always lead to the outcome, but increases the chance (or the risk) of it happening. In order to claim that the factor causes the outcome we need to identify a process or mechanism that might account for the observed correlation.

1. use ideas about correlation and cause to:

identify a correlation in data presented as text, in a table, or as a graph

distinguish between a correlation and a cause effect link

suggest factors that might increase the chance of a particular outcome in a given situation, but do not invariably lead to it

explain why individual cases do not provide convincing evidence for or against a correlation

identify the presence (or absence) of a plausible mechanism as reasonable grounds for accepting (or rejecting) a claim that a factor is a cause of an outcome

eg  evidence for risks of X-rays (P1.2), evidence for human activities causing global warming (P1.3)

Scientific explanations and theories do not ‘emerge’ automatically from data, and are separate from the data. Proposing an explanation involves creative thinking. Collecting sufficient data from which to develop an explanation often relies on technological developments that enable new observations to be made.

As more evidence becomes available, a hypothesis may be modified and may eventually become an accepted explanation or theory.

A scientific theory is a general explanation that applies to a large number of situations or examples (perhaps to all possible ones), which has been tested and used successfully, and is widely accepted by scientists. A scientific explanation of a specific event or phenomenon is often based on applying a scientific theory to the situation in question.

2. describe and explain examples of scientific methods and theories that have developed over time and how theories have been modified when new evidence became available

eg Climate change (P1.3), Big Bang model (P4.5), Nuclear model of the atom (P5.1), The link between work, heat and temperature (P6.2)

Findings reported by an individual scientist or group are carefully checked by the scientific community before being accepted as scientific knowledge. Scientists are usually sceptical about claims based on results that cannot be reproduced by anyone else, and about unexpected findings until they have been repeated (by themselves) or reproduced (by someone else).

Two (or more) scientists may legitimately draw different conclusions about the same data. A scientist’s personal background, experience or interests may influence his/her judgments.

An accepted scientific explanation is rarely abandoned just because new data disagree with it. It usually survives until a better explanation is available.

3. describe in broad outline the ‘peer review’ process, in which new scientific claims are evaluated by other scientists

eg Telescopes and the Big Bang model (P4.5)

Models are used in science to help explain ideas and to test explanations. A model identifies features of a system and rules by which the features interact. It can be used to predict possible outcomes. Representational models use physical analogies or spatial representations to help visualise scientific explanations and mechanisms. Descriptive models are used to explain phenomena. Mathematical models use patterns in data of past events, along with known scientific relationships, to predict behaviour; often the calculations are complex and can be done more quickly by computer.

Models can be used to investigate phenomena quickly and without ethical and practical limitations, but their usefulness is limited by how accurately the model represents the real world.

4. use a variety of models (including representational, spatial, descriptive, computational and mathematical models) to:

solve problems, make predictions, develop scientific explanations and understanding, identify limitations of models

eg Radiation model of light (P1.2); Wave model of light (P1.3); Physical analogies of electric circuits (P2.2, P2.3) Equations of motion(P4.2) Atomic model (P5.1) Particle model of matter (P6.1, P6.2)
 


Chapter IaS4 How do science and technology impact society?

Science and technology provide people with many things that they value, and which enhance their quality of life. However some applications of science can have unintended and undesirable impacts on the quality of life or the environment. Scientists can devise ways of reducing these impacts and of using natural resources in a sustainable way (at the same rate as they can be replaced).

Everything we do carries a certain risk of accident or harm. New technologies and processes can introduce new risks.

The size of a risk can be assessed by estimating its chance of occurring in a large sample, over a given period of time.
 

To make a decision about a course of action, we need to take account of both the risks and benefits to the different individuals or groups involved. People are generally more willing to accept the risk associated with something they choose to do than something that is imposed, and to accept risks that have short-lived effects rather than long-lasting ones. People’s perception of the size of a particular risk may be different from the statistically estimated risk. People tend to over-estimate the risk of unfamiliar things (like flying as compared with cycling), and of things whose effect is invisible or long-term (like ionising radiation).

Some forms of scientific research, and some applications of scientific knowledge, have ethical implications. In discussions of ethical issues, a common argument is that the right decision is one which leads to the best outcome for the greatest number of people.

Scientists must communicate their work to a range of audiences, including the public, other scientists, and politicians, in ways that can be understood. This enables decision-making based on information about risks, benefits, costs and ethical issues.

1. describe and explain everyday examples and technological applications of science that have made significant positive differences to people’s lives

Positive applications of science: use of the electromagnetic spectrum (P1.2); development of electromagnetism and electric motors (P2.4, P2.5); generating and distributing electricity (P3.3); road safety (P4.3);

Sustainability: energy demands and choices of sources to generate electricity (P3.2)

Risks, benefits and ethical issues: biodiversity (B6.4) technologies that use ionising radiation (P1.2, P5.2); energy sources to generate electricity (P3.2, P3.3, P5.3);

2. identify examples of risks that have arisen from a new scientific or technological advance

3. for a given situation:

- identify risks and benefits to the different individuals and groups involved

- discuss a course of action, taking account of who benefits and who takes the risks

- suggest reasons for people’s willingness to accept the risk

- distinguish between perceived and calculated risk (HT only)

4. suggest reasons why different decisions on the same issue might be appropriate in view of differences in personal, social, economic or environmental context, and be able to make decisions based on the evaluation of evidence and arguments

5. distinguish questions that could in principle be answered using a scientific approach, from those that could not; where an ethical issue is involved clearly state what the issue is and summarise the different views that may be held

6. explain why scientists should communicate their work to a range of audiences.


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