Key term
CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Deformation of Solids
Thermal Physics
Topic overviewBoyle's law, Charles's law and the pressure lawThe ideal gas equation pV = nRTThe Avogadro constant, the mole and pV = NkTInternal energy and the distribution of molecular energyThe kinetic theory equation pV = ⅓Nm⟨c²⟩Average molecular kinetic energy and temperatureAbsolute zero and the kelvin scaleSpecific heat capacity and the electrical method
Uniform Circular Motion
Simple Harmonic Motion
Topic overviewDefining simple harmonic motion and a = −ω²xDisplacement, velocity and acceleration: x = A cos ωtThe simple pendulum and T = 2π√(l/g)The loaded spiral spring and T = 2π√(m/k)SHM graphs and finding velocity from a gradientFree vibrations, forced vibrations and resonanceDamping: light, critical and over-damping
The Nucleus and Radioactive Decay
Topic overviewAlpha-particle scattering and the nuclear atomNuclear radius and nucleon numberThe density of nuclear matterAlpha, beta and gamma radiation: nature, penetration and rangeNuclear equations and changes in nucleon and proton numberThe random and exponential nature of radioactive decayActivity, the decay constant and A = −λNExponential decay calculations with A = A₀e^(−λt)Half-life and measuring it
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Thermal Physics
Internal energy and the distribution of molecular energy
- 3 things to know
- Unit A2 1
Overview
Internal energy of a substance and temperature and internal energy.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Define the internal energy of a substance.
Key term
Why does the internal energy of a fixed mass of ideal gas depend only on its temperature?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define the internal energy of a substance.
Model answer
The internal energy of a substance is the sum of the randomly distributed kinetic and potential energies of all of its molecules.
- 2
What form of energy makes up the internal energy of an ideal gas, and why?
Model answer
It is entirely kinetic, because an ideal gas has no intermolecular forces and therefore no molecular potential energy.
- 3
Why does the internal energy of a fixed mass of ideal gas depend only on its temperature?
Model answer
The internal energy is the total random kinetic energy of the molecules, and the mean molecular kinetic energy is directly proportional to the absolute temperature.
- 4
Explain what is meant by saying that molecular energies are randomly distributed.
Model answer
At any instant the molecules have a wide spread of speeds and energies in all directions, and an individual molecule's energy changes constantly through collisions, so only the average over the whole sample is a fixed quantity.
- 5
Where does the potential energy contribution to internal energy come from in a liquid or a solid?
Model answer
It comes from the work done against the forces of attraction between molecules held close together, which is why liquids and solids have molecular potential energy while an ideal gas does not.
- 6
Why does the temperature of a substance remain constant while it is melting even though it is being heated?
Model answer
The energy supplied is doing work against the intermolecular forces, increasing the molecular potential energy rather than the molecular kinetic energy, so the mean kinetic energy and hence the temperature do not change.
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