GCSE Physics Paper 1

How many energy stores do we need to know?

8

What is an energy store?

The way that energy is held or contained within an object

What are the energy stores that we need to know?

Kinetic, Thermal (Internal), Chemical, Electrostatic, Magnetic, Nuclear, Gravitational Potential, and Elastic Potential

What is kinetic energy?

The energy an object has because of its motion

What is an example of kinetic energy?

A bouncing basketball

What does more kinetic energy mean?

A faster speed

What two things does kinetic energy depend on? What does this mean?

An object’s mass and speed—the greater the mass and the faster the speed, the more energy in its kinetic energy store

What is thermal/internal energy?

The total kinetic energy and potential energy of all the particles within a system, which determines its temperature

What is an example of internal energy?

Boiling water on a stove

What is chemical energy?

Energy stored within chemical bonds, which is released or absorbed during a chemical reaction

What is an example of chemical energy?

It is stored in food

What is electrostatic energy?

Energy due to the forces between stationary electric charges

What is an example of electrostatic energy?

A charged balloon sticking to a wall

What is magnetic energy?

Energy stored in a magnetic field when magnetic poles are pushed together or pulled apart

What is an example of magnetic energy?

A maglev train

What is nuclear energy?

Energy stored within the nucleus of an atom and released when it is split (fission) or joined to other nuclei (fusion)

What is an example of nuclear energy?

Nuclear power plants

What is gravitational potential energy (GPE)?

Energy stored in an object due to its height

What is an example of GPE?

Water held behind a dam

Why do high up objects have GPE?

Lifting an object in a gravitational field requires work, so energy is transferred to the GPE store of higher objects

What three things does GPE energy depend on? What does this mean?

Mass, height, strength of gravitational field—the greater the mass, height and GFS, the more energy is stored in the GPE store

When an object falls, why does GPE energy lost ≠ kinetic energy gained?

Air resistance—some energy is transferred to other energy stores instead, such as the thermal stores of the object and surroundings

What is elastic potential energy (EPE)?

Energy stored as a result of stretching or compressing an elastic object to elastically deform it

What is an example of EPE?

Stretching a rubber band

What is energy transfer?

When a system changes (when something happens), stored energy is transferred from one store to another, and so as one empties, the other fills

What is a system?

Simply the object or group of objects that you’re interested in

What is a closed system?

A system where neither matter nor energy can enter or leave—energy can transfer between stores within the system, but the net change in energy is always zero

Which of the energy stores are solely potential energy stores, and what does this mean?

Chemical, Electrostatic, Magnetic, Nuclear, Gravitational and Elastic — stored-up energy

Which of the energy stores are solely non-potential/active energy stores and what does this mean?

Kinetic energy — energy in action

Is internal energy potential energy or active energy?

Both — it is composed of both kinetic and potential energy

How many pathways do we need to know?

4

What are pathways?

Processes by which energy is transferred from one source to another

What are the pathways we need to know?

Mechanical, Electrical, Heating and Radiation

What is the mechanical pathway?

Transfer by a force doing work, such as moving an object

What is an example of the mechanical pathway?

A wind turbine

What is the electrical pathway?

Transfer by charges doing work (moving) in a circuit

What is an example of the electrical pathway?

Lighting a lightbulb

What is the heating pathway?

Transfer by a temperature difference, from a hotter area to a colder one, such as by conduction or convection

What is an example of the heating pathway?

Freezing water

What is the radiation pathway?

Transfer by waves, such as electromagnetic (EM) waves (light, infrared, radio etc) or mechanical waves (sound, ultrasound, water waves etc)

What is an example of the radiation pathway?

Heating food in a microwave

What is the process of energy transfer when turning on a torch (using arrows)?

Chemical energy store (of the battery) [VIA ELECTRICAL PATHWAY (THROUGH A CIRCUIT)] —> Thermal energy store (of the lamp) [VIA {LIGHT} RADIATION PATHWAY (THROUGH LIGHT WAVES] —> Thermal energy store (of the surroundings)

What is the process of energy transfer when turning on a motor (using arrows)?

Chemical energy store (of the battery) [VIA ELECTRICAL PATHWAY (THROUGH A CIRCUIT)] —> Kinetic energy store (movement of the motor) AND Thermal energy store (heat due to friction and electrical resistance)

What is the law of energy conservation?

Energy cannot be created or destroyed — it can only be transferred, stored or dissipated

What is energy?

A measure of a system’s ability to do work (or more technically the measure of a system’s mass-energy state, where mass is a concentrated form of energy)

What is work?

When something is moved with a force (in the direction of the force)

What are energy and work done measured in?

Joules (J) or kilojoules (kJ)

What is the mathematical definition for when 1J of work has been done, and so which units are equivalent?

1J of work has been done when a force of 1N causes a displacement of 1m, so 1J = 1 Nm

What is the difference between the units Joules and Newton-metres?

Joules are used for energy and are a scalar value (has magnitude but no direction) and so force and movement are in the same direction, whilst Newton-metres are more used for moments and turning forces and are a vector (has both magnitude and direction) and so force and movement are not in the same direction

What is the equation for work done and force? If the object doesn’t move has work been done? What about if no force is applied?

Work done = force x distance moved (in the direction of the force), and so no to both, because 0f or 0d would mean W would = 0

When is work done positive? With an example?

When force helps an object move, such as pushing a box (the ending energy is greater)

When is work done negative? With an example?

When force tries to stop an object moving, such as braking a car (the ending energy is less)

What is the approximate gravitational field strength (gfs) of Earth? How can we use this to convert mass to weight on Earth?

9.8, so multiply mass (kg) by 9.8 to get weight (N)

How does a lamp dissipate energy (include all stores and pathways)?

• Chemical energy (battery) [VIA ELECTRICAL] —> Thermal energy (lamp) [VIA {LIGHT} RADIATION] —> surroundings

• This light is usefully transferred

• However, it also gets warm, wasting energy by transferring energy as heat to the thermal store of the surroundings via radiation/heating

What is energy mostly dissipated as? Why?

Heat — due to friction, electrical resistance and escaped heat

Does wasted energy disappear? What happens to it?

No, it is simply in a form that is not useful to us at that moment

What is friction caused by?

Forces between two things when they touch—closer up, all objects are much rougher, no matter how smooth they look or feel, and as they move across each other, the jagged bits on the two surfaces snag against each other

What is the direct impact of friction?

It slows down the force—does negative work

What is the kinetic energy of friction transferred to?

Thermal energy

What is a lubricant?

A liquid or gas introduced between two solids to reduce friction and wear

How does a lubricant work?

The liquid/gas can easily change shape and flow, so smooths and cushions the bumps, meaning the layers will slide freely past one another, reducing friction, as well as wear and tear

How does lubrication reduce wear and tear in machinery?

Less grinding means that less metal is scraped off, so the parts last longer

What are 5 ways to insulate a home so that heat doesn’t escape? How do they work?

• Thick walls with low thermal conductivity (slower rate of energy transfer)

• Cavity walls (air gap between inner and outer walls reduces conduction, foam between walls also reduces convection)

• Attic insulation (reduces conduction and convection)

• Double glazing (air gap between two panes reduces conduction)

• Draught excluders (around doors and windows—reduces convection)

What would be the independent, dependent and key control variable when testing different materials’ insulation capabilities?

• IV: material

• DV: temperature difference

• CV (key): time

How does temperature difference between inside and outside affect energy transfer?

The greater the temperature difference, the faster heat is lost to the surroundings

What does a Sankey energy diagram show?

How much of the energy that goes into a machine is used usefully or is wasted

What does the arrow on the left of a Sankey energy diagram show?

How much energy goes in

What does the arrow straight ahead from the initial arrow on a Sankey energy diagram show?

How much energy is transferred usefully

What do the arrow(s) going down on a Sankey energy diagram show?

How much energy is wasted

What else is added to a Sankey energy diagram other than arrows?

Labels to show the type of energy referred to

In a Sankey energy diagram, what is used to show how much energy is transferred? What has no significance?

Thickness of arrow, to scale, shows how much energy is transferred—length of arrow has no significance

What is Power?

The rate at which you do work/transfer energy

What are the units of power?

Watts (W) or kilowatts (kW)

Which equation defines Power? What does this mean?

• Power = energy transferred/time taken (P = ΔE/t)

• 1W = 1J transferred per second (1/1=1)

Which symbol shows a change or difference in something?

Δ (A triangle—Greek letter delta)

What is efficiency?

A measure of how ‘good’ a device is at converting the energy input into useful energy with minimal dissipation

What is the equation for efficiency?

Efficiency = useful energy out/total energy in (η = useful energy/total energy)

What is the symbol for efficiency?

η (n with a long right leg—Greek letter eta)

What range will efficiency always be in? Why?

0–1 (0%—100%), because energy cannot be created or destroyed

What is the only system that is usually 100% efficient? Why?

Electric heaters—all the energy is transferred to useful thermal stores

How does a hot cup of coffee cool down in terms of stores and pathways? Why?

The hot coffee transfers its thermal energy via the heating pathway to the thermal energy store of the surroundings—heat flows from a warmer area to a colder one

What is conduction?

When heat is transferred through a solid by vibrations of the particles, which collide with each other and transfer the heat—these vibrations get bigger as the solid is heated and gains internal energy

Why are solids better conductors than liquids and gases?

The particles are very close together

Why are metals better conductors than non-metals?

Thermal energy can be carried by free delocalised electrons, which can collide frequently with other electrons and ions to transfer kinetic energy faster

What are materials with good thermal conductivity called? Poor thermal conductivity?

Conductors, insulators

What are two ways to reduce an object’s rate of conduction (with examples)

Changing the state or size—melting reduces intrinsic conductivity by changing a solid to a liquid, reshaping an object to make it longer reduces rate of conduction means that the vibrations/collisions have further to travel

Can reshaping an object affect its conductivity? Why?

No—it could affect the rate of conduction, but its conductivity is an intrinsic property of the material

Can melting an object affect its conductivity? Why?

Yes—the substance literally changes state

What is convection?

Thermal energy transfer in liquids and gases, where particles move from hotter to cooler areas, because heating makes particles gain kinetic energy, meaning they spread out more, decreasing density, so the warmer fluid rises

What is a convection current and how does it work?

A continuous cycle of fluid movement caused by a constant heat source -

• Energy is transferred to nearby particles, increasing their kinetic energy, making them spread out, become less dense and rise

• Cooler, denser fluid moves in to take the place of the rising warm fluid

• The warmer fluid transfers energy to its surroundings, so cools, becomes denser, cools, and sinks

• The cycle continuously repeats, creating a circulating flow of fluid

What is a way of generating energy called?

An energy resource

What does most of the energy we get today come from?

Burning fossil fuels

What is a non-renewable resource?

A resource that is finite, meaning it will not last forever and will eventually run out

What is a renewable resource?

A resource that can be replenished at least as fast as it is used

What are fossil fuels?

Resources formed over millions of years from the buried remains of ancient organic matter, formed under heat and pressure, such as coal, oil and natural gas

What are 9 advantages of fossil fuels?

• It is a reliable source of energy (can generate electricity on demand at any time)

• It has the capacity to generate large amounts of energy

• It has a high energy density (releases a large amount of energy per kilogram of fuel)

• It is comparatively inexpensive

• Transporting oil and gas is easy (they are fluids which can be transported through pipelines)

• Fossil fuel power stations can be located anywhere

• Fossil fuels are abundant

• Gas-fuelled power stations have a short start-up time

• It can quickly increase the amount of electricity generated to cope with sudden increases in demand

What are 4 disadvantages of fossil fuels?

• Pollution by carbon dioxide (it is a greenhouse gas which traps infrared radiation emitted by the Earth’s surface, leading to global warming and climate change)

• Causing acid rain (by releasing sulphur dioxide and nitrogen oxides into the atmosphere, which react with water and oxygen in clouds to form acids, which fall as acid rain and acidify soil and water, damaging plants and animals)

• They are non-renewable (they will eventually run out—this also leads to increasing cost as they become less abundant or have environmental taxes placed on them)

• It can cause visual pollution

What are nuclear fuels?

When the nucleus of an atom (uranium or plutonium) is split, releasing a huge burst of thermal energy, which is used to boil water into steam and spin a generator

What are 5 advantages of nuclear fuels (one being similarities with fossil fuels)?

• They don’t emit greenhouse gases or cause acid rain

• They’re cheaper than fossil fuels

• They produce huge amounts of energy (10,000x as much energy as fossil fuels)

• They have a much higher energy density than fossil fuels (1kg of nuclear fuel releases the same amount of energy as burning 2,000,000kg of coal)

• Alike fossils fuels, they are also reliable, and the raw fuel is easy to transport

What are 3 disadvantages of nuclear fuels?

• They have a long start-up time (they take time to safely set up)

• They cannot react to demand spikes (it would be unsafe, as there are risks of meltdown, control loss and structural damage)

• There are sometimes accidents, which can release very dangerous radioactive waste, that stays radioactive for thousands of years, which is harmful to living organisms and the environment