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180 Cards in this Set
- Front
- Back
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Triple point |
The point of temperature and pressure at which a substance can exist in the three phases of matter in thermal equilibrium. |
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Thermal equilibrium |
A state in which there is no net flow of thermal energy between the objects involved. |
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Description of the structure of a solid |
Made of particles in a regular structure Strong forces of attraction between the particles Particles cannot move out of their positions When heated the particles gain energy and vibrate more |
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Description of the structure of a liquid |
Particles are free to move around The structure has no fixed shape There are still forces of attraction between the particles |
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Description of a liquid |
Particles are far apart Takes up more volume because of particle spacing Almost no forces of attraction between the particles |
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Internal energy |
The sum of the randomly distributed kinetic and potential energies of the atoms, molecules or ions within a substance |
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Specific heat capacity |
The energy required per unit mass to raise the temperature of a substance by 1K |
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Assumptions of the kinetic model |
A gas consists of a large number of molecules in rapid, random motion No inter-molecular forces exist except during collisions The gravitational force on the molecules is negligible Collisions between the gas particles and the container are elastic The volume of the particles is negligible compared to the volume of the container |
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Brownian motion |
The continuous random motion of particles suspended in a fluid |
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Conclusions of Brownian motion |
A gas consists of a large number of molecules in rapid, random motion |
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The zeroth law of thermodynamics |
If two objects are in thermal equilibrium with a third then all three are in equilibrium with each other |
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Electrostatic potential energy of a gas |
Zero because there are negligible electrical forces between the particles |
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Electrostatic potential energy of a liquid |
Negative value meaning energy must be supplied to break apart molecular or atomic bonds |
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Electrostatic potential energy of a solid |
Large negative value due to strong electrostatic forces |
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Equation for specific heat capacity |
c = E / (m * change in temperature) |
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Specific latent heat |
The energy required to change the phase of a substance per unit mass |
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Specific latent heat of fusion |
The energy required per unit mass of a substance to change it from a solid to a liquid |
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Specific latent heat of vaporisation |
The energy required per unit mass of a substance to change it from a liquid to a gas |
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Equation for energy in a circuit |
E = IVt This is because P = IV |
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Molar mass |
The mass of one mole of one substance |
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Mole |
The amount of substance that contains 6.02 *10^23 elementary entities |
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The Avogadro constant |
6.02 * 10^23 Symbol = Na |
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The equation for the number of atoms or molecules in a substance |
N = n * NA Where n = number of moles NA = Avogadro constant |
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The mass of one mole of a substance |
The mass of number of the substance in grams |
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Equation for number of moles in a substance |
mass / molar mass |
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Boyle's law |
The pressure of an ideal gas is inversely proportional to its volume provided the mass and temperature is constant pV = constant |
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Charles' law |
The volume of an ideal gas at constant mass and volume is directly proportional to its absolute temperature (kelvin) p/T = constant |
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Molar gas constant |
The constant in the combined gas law equation of an ideal gas. Symbol = R 8.31Jk^-1mol^-1 |
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Combined gas law equation |
pV / T = R Where p = pressure, V = volume, T = temperature and R = molar gas constant |
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Nebula |
A cloud of dust and gas (mainly hydrogen), often many hundreds of times larger than our solar system |
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Protostar |
A hot and dense sphere of condensing dust and gas that is in the process of becoming a star |
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Nebula to Protostar |
Part of the Nebula becomes very dense and gravitational energy is transferred into kinetic energy |
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Protostar to Star |
Nuclear fusion must start in the core. High pressures and temperatures are needed to overcome electostatic respulsion between hydrogen nuclei |
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Radiation pressure |
Pressure from the photons in the core of a star, which acts outwards and counteracts the pressure from gravity pulling matter inwards |
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Gas pressure |
In stars, the pressure of the nuclei in the star's core pushing outwards and counteracting the pressure from gravity pulling matter inwards |
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Main sequence |
The main period of a star's life during which it is stable with almost constant size |
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Planet |
An object in orbit around a star with a mass large enough for its gravity to give it a round shape, that undergoes no fusion reactions and that has cleared its orbit of most other objects |
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The equation for pressure and volume of an ideal gas |
pV = nRT Where p = pressure, V = volume, n = number of moles, R = Gas constant and T = temperature |
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Equation for pressure and volume of a gas using r.m.s |
pV = 1/3Nm(mean squared speed) Where p = pressure, V = volume, N = number of particles and m = mass of each particle |
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Method to find r.m.s |
Square the speed of each particle in the gas and find the mean of this. Square root the mean of the speeds squared |
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Maxwell-Boltzmann distribution |
The distribution of speeds of particles in a gas |
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Trends of Maxwell-Boltzmann distribution with temperature |
Changing the temperature changes the distribution. The distribution becomes more spread out as the gas becomes hotter and the r.m.s increases. |
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Boltzmann constant |
The molar gas constant R divided by the Avogadro constant Na, a constant that relates the mean kinetic energy of the atoms or molecules in a gas to the gas temperature - symbol k |
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Equation for pressure and volume of an ideal gas using k |
pV = NkT Where p = pressure, V = volume, N = number of particles, k = Boltzmann constant and T = temperature |
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Equation for molar gas constant |
R = Na * k |
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Equation to directly relate mean kinetic energy of particles in a gas to absolute temperature |
1/2m(mean squared speed) = 3/2kT Where m = mass of each particle, k = Boltzmann constant and T = temperature |
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Equation for mean kinetic energy of particles in a gas |
E = 1/2m(mean squared speed) |
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Relationship between average kinetic energy of particles in a gas and temperature |
Directly proportional |
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Radian |
The angle subtended by a circular arc with length equal to the radius of the circle |
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Equation for angle in radians |
Angle in radians = Arc length / Radius |
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Angular velocity |
The rate of change of angle for an object moving in a circular path Unit - radians per second |
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Equations for angular velocity |
omega = theta / t omega = 2Pi / T omega = 2Pi * f Where omega = angular velocity, t = time, T = time period and f = frequency |
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Centripetal acceleration |
The acceleration of any object travelling in a circular path at constant speed, which always acts towards the centre of the circle |
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Equation for linear velocity |
v = r(omega) Where r = radius and omega = angular velocity |
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Relationship between linear velocity and radius |
Directly proportional |
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Equations for centripetal acceleration |
a = v^2 / r a = omega^2 * r |
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Centripetal force |
A force that keeps a body moving with a constant speed in a circular path |
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Equations for centripetal force |
F = mv^2 / r F = m * (omega)^2 * r Where m = mass, v = velocity, r = radius and omega = angular velocity |
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Oscillating motion |
Repetitive motion of an object around its equilibrium position |
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Equilibrium postition |
The resting position of waves or particles in an oscillation |
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Displacement (oscillations) |
The distance from the equilibrium position |
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Amplitude |
The maximum displacement from the equilibrium position |
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Period |
The time taken to complete one full oscillation |
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Frequency (oscillations) |
The number of oscillations per unit time |
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Phase difference (oscillation) |
The difference in displacement between two oscillating objects Symbol theta |
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Maximum phase difference |
Pi radians |
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Angular frequency |
A quantity used in oscillatory motion - equal to the product of frequency f and 2Pi |
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Equations for angular frequency |
Omega = 2Pi / T Omega = 2Pi *f Where omega = angular frequency, T = time period and f = frequency |
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Simple harmonic motion |
Oscillating motion for which the acceleration of the object is directly proportional to its displacement and in the opposite direction of the displacement |
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Equation for acceleration in simple harmonic motion |
a = -(omega)^2 * x Where (omega)^2 is a constant for the object and x = displacement |
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Relationship between time period and amplitude in SHM |
They are independent |
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Point in an oscillation where velocity is maximum |
Equilibrium |
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Point in oscillation where acceleration is maximum |
Amplitude |
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Isochronous oscillator |
An oscillator that has the same period regardless of amplitude SHM is isochronous |
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Equations for displacement in SHM |
x = Asin(Omega * t) x = Acos(Omega * t) Where A = amplitude, Omega = angular frequency and t = time |
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Equation for velocity of a simple harmonic oscillator |
V = + or - (Omega) * (A^2 - x^2)^-1/2 Where omega = angular frequency, A = amplitude and x = displacement |
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Equation for maximum velocity of a simple harmonic oscillator |
Vmax = (Omega) * A Where Omega = angular frequency and A = amplitude |
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Total energy on an energy displacement graph of SHM |
Constant |
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Point of maximum kinetic energy in SHM |
Equilibrium |
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Point of minimum kinetic energy in SHM |
Amplitude |
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Point of maximum potential energy in SHM |
Amplitude |
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Point of minimum potential energy in SHM |
Equilibrium |
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Potential energy in a spring equation |
E = 1/2k * x^2 Where k = spring constant and x = extension |
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Equation for total energy in an SHM spring |
E = 1/2k * A^2 Where k = spring constant and A = amplitude |
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Equation for kinetic energy in an SHM spring |
E = 1/2k(A^2 - X^2) Where k = spring constant, A = amplitude and x = displacement |
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Damping |
An oscillation is damped when an external force that acts on the oscillator has the effect of reducing the amplitude of its oscillations |
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Light damping |
Damping that occurs when the damping forces are small and the period of the oscillations is almost unchanged |
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Heavy damping |
Damping that occurs when the damping forces are large and the period of the oscillations increases slightly with the rapid decrease in amplitude |
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Free oscillation |
The motion of a mechanical system displaced from it equilibrium position and then allowed to oscillate without any external forces |
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Natural frequency |
The frequency of a free oscillation |
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Forced oscillation |
An oscillation in which a periodic driver force is applied to an oscillator |
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Driving frequency |
The frequency with which the periodic driver force is applied to a system in forced oscillation |
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Frequency of forced oscillations |
Driving frequency |
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Resonance |
The increase in amplitude of a forced oscillation when the driving frequency matches the natural frequency of the oscillating system |
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Equation for specific latent heat |
L = E / m Where L = specific latent heat, E = energy and m = mass E is the energy supplied to change the state of mass m of the substance |
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Variables kept constant for Charles' law |
Volume and mass P / T = constant |
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Variables kept constant for Boyle's law |
Temperature and mass |
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Gravitational field strength |
The gravitational force exerted per unit mass at a point within a gravitational field |
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Equation for g and unit |
g = F / m N / kg |
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Gravitational field lines |
Lines of force used to map the gravitational field pattern around an object |
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Rules of graviational field lines |
The lines do not cross A stronger field is represented by lines that are closer together The lines all point towards the centre of mass of the object creating the field |
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Radial field |
A symmetrical field that diminishes with distance squared from its centre, such as the gravitational field around a spherical mass |
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Uniform gravitational field |
A gravitational field in which the field lines are parallel and the value for g remains constant. |
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Newton's law of gravitation |
The gravitational force between two point masses is: Directly proportional to the product of the masses Inversely proportional to the square of the seperation |
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Equation for Newton's law of gravitation |
F = GMm / r^2 Where G = gravitational constant, Mm = product of masses and r = distance of seperation |
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Equation for gravitational field |
g = GM / r^2 Where G = Gravitational constant, M = mass of the object creating the field and r = separation |
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Proportional relationships in a radial gravitational field |
g is directly proportional to the mass of the object creating the field g is inversely proportional to the square of the distance from the centre of mass of the object g is not affected by the mass of the object in the field |
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Gravitational field strength in a uniform field |
Constant |
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Kepler's first law of planetary motion |
The orbit of a planet is an ellipse with the sun at one of the two foci |
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Kepler's second law of planetary motion |
A line segment connecting a planet to the sun sweeps out equal areas during equal intervals of time |
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Ellipse |
A squashed or elongated circle with two foci |
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Rammification of kepler's second law of planetary motion |
Planets do not orbit the sun with constant speed |
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Kepler's third law of planetary motion |
The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the sun T^2 / r^2 = k |
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Equation for velocity of a planet in a circular orbit |
v^2 = GM / r Where G = gravitational constant, M = mass of object creating the gravitational field and r = separation |
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Equation for time period of a planet in a circular orbit |
T^2 = (4Pi^2 / GM) * r^3 Where G = gravitational constant, M = mass of object creating the gravitational field and r = separation |
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Gradient of a graph of T^2 against r^3 |
(4Pi^2 / GM) Where G = gravitational constant and M = mass of object creating the gravitational field |
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Forces that hold a star in main sequence |
Pressure from gravity matches radiation pressure from fusion and gas pressure from nuclei in the core. |
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Solar mass |
The mass of the sun |
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Red giant |
An expanding star at the end of its life, with an inert core in which fusion no longer takes place, but in which fusion of hydrogen to helium still continues around the core |
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Main sequence to red giant |
The star runs out of nuclei to fuse in its core and the core begins to shrink because gravity overcomes gas and radiation pressure |
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Reason for fusion in the shell of a red giant |
As the core shrinks pressure in the shell around it increases enough for fusion to occur |
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Effect of fusion occuring in the shell of a red giant |
The peripheral layers of the star expand and cool. This is why the star is red. |
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Criteria to become a red giant star |
Mass must be between 0.5 and 10 solar masses |
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White dwarf |
A very dense star formed from the core of a red giant in which no fusion occurs Energy is only emitted by leaked photons |
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Red giant to white dwarf |
The outer layers of the red giant drift into space as a planetary nebula. This leaves the core as a white dwarf |
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Electron degeneracy pressure |
A quantum-mechanical pressure created by the electrons in the core of a collapsing star due to the pauli exclusion principle |
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Chandrasekhar limit |
The mass of a star's core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse. 1.44 solar masses |
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Red supergiant |
An expanding star that has mass greater than 10 solar masses. |
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Main sequence to red supergiant |
The star begins to run out of hydeogen to fuse. The star begins to fuse heavier elements and the star expands with a series of shells of fusion of different elements inside the star |
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Reason red supergiants fuse heavier elements |
The core of the star has such high temperature and pressure that the helium nuclei produced by the hydrogen fusion are moving fast enough to overcome electrostatic repulsion and fuse. |
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Red supergiant to supernova |
The red supergiant develops an iron core. Since the fusion of iron produces no energy, the star becomes unstable. This means the layers implode, bounce off of the solid iron core and are ejected into space. |
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Supernova |
The implosion of a red supergiant at the end of its life, which leads to the subsequent ejection of stellar matter in to space leaving an inert remnant core |
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Neutron star |
The remnant core of a massive star made almost entirely of neutrons that has gone supernova and has collpased to an extremely high density |
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Requirements for a core of a star to become a nuetron star |
The core must exceed the Chandrasekhar limit of 1.44 solar masses |
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Supernova to Neutron star |
The remnant core of a red supergiant that has become a supernova collapses to an extremely high density |
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Requirement for the core a star to become a black hole |
Mass must exceed three solar masses |
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Black hole |
The remnant core of a massive star after it has gone supernova and the core has collapsed so far that in order to escape it an object would need an escape velocity greater than the speed of light |
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Hertzsprung-Russell (HR) diagram |
A graph showing the relationship between their luminosity on the y axis and their average surface temperature on the x axis with temperature increasing from right to left |
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Luminosity |
The total radiant power output of a star Unit Watts |
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Effect of surface area on luminosity |
Increasing surface area increases luminosity |
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Point when internal energy increases when a substance is being heated |
When the substance is changing state |
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Specific heat capacity |
The energy required to raise the temperature of 1kg of a substance by 1 kelvin |
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Equation for specific latent heat |
L = E / m |
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Assumptions for an ideal gas |
Large number of molecules with random speeds and directions Molecules occupy negligible volume compared volume of the gas All collisions are perfectly elastic Collisions take a negligible amount of time Electrostatic forces are negligible except during collisions |
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Energy level |
A discrete amount of energy that an electron within an atom is able to possess |
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Ground state |
The energy level with the most negative value possible for an electron within an atom |
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Requirement for excitement of an electron |
External energy must be supplied to the atom from an electric field, heat or a photon |
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Effect of an electron moving to a lower energy level and reason |
A photon is emitted. This is because energy must be conserved |
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Equations that can be used to calculate the change in energy of an electron |
E = hf = hc / lamda The energy of the photon emitted or absorbed |
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Spectral line |
A line in an emission line spectrum or absorption line spectrum at a specific wavelength |
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Emission line spectrum |
Each element produces a unique spectrum of bright emission lines because its unique energy levels |
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Continuous spectrum |
All visible frequencies or wavelengths are present A solid metal will produce this (filament lamp for example) |
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Absorption line spectrum |
A spectrum of dark lines against a continuous background. The lines are the same wavelength as they would be for emission |
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Requirement for an atom to absorb a photon and excite an electron |
The photon must have energy exactly equal to the difference between energy levels |
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Process to create an emission line spectrum |
Electrons in a hot gas are excited When the gas cools the electrons move to lower energy levels and release photons that have wavelengths specific to the element |
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Process to create an absorption line spectrum |
Light from a source that creates a continuous spectrum passes through a cool gas Photons of energy exactly equal to the energy level difference are absorbed by the atoms Therefore specific wavelengths of light cannot be seen |
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Relationship between max wavelength and absolute temperature of a black body at maximum intensity |
They are inversely proportional |
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Wien's displacement law |
The peak wavelength at which the intensity of radiation from a black body is a maximum is inversely proportional to the absolute temperature of the black body |
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Stefan's law equation |
L = 4Pi * r^2 * T^4 * stefan constant Where r = radius and T = surface temperature |
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Values proportional to luminosity of a star from stefan's law |
radius squared to its surface area to its absolute temperature |
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Astronomical unit
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The average distance from the Earth to the Sun 1.5 * 10^11m |
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Definition of a parsec |
The distance at which a radius of 1 astronomical unit subtends an angle of 1 arcsecond |
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Stellar parallax |
A technique used to measure the distance of stars from the earth when they are less than 100pc away |
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Method using of stellar parallax |
The parallax angle between two positions of a star is measured between 6 months as the Earth moves |
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Equation to use parallax angle |
d = 1 /p
Where d = distance from the star in parsecs and p = parallax angle in arcsecs |
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Explanation of arcseconds and arcminutes |
There are 60 arcseconds in an arcminute and there are 60 arcminutes in a degree |
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Doppler effect |
The change in wavelength and frequency of waves received from an object moving relative to an observer |
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Doppler equation |
delta lamda / lamda = delta f / f = v / c
Where lamda = source wavelength, delta lamda = change in wavelength, f = source frequency, delta f = change in frequency, v = magnitude of relative velocity and c = speed of light |
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Hubble's law |
The recessional speed of a galaxy is almost directly proportional to its distance from the Earth |
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Equation for Hubble's constant |
v = Ho * d Where v = recessional speed, d = distance of the galaxy from Earth and Ho = Hubble constant |
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Unit for the Hubble constant |
kilometres per second per megaparsec |
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The Big Bang theory |
The theory that at a moment in the past, all the matter in the Universe was contained in a singularity, the beginning of space and time, that expanded rapidly outwards |
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Evidence for the Big Bang theory |
Hubble's law Microwave background radiation |
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Microwave background radiation |
The microwave signal of uniform intensity detected from space, which fits a black body at 2.7k |
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Black body |
An idealised object that absorbs all electromagnetic radiation incident upon it and, when in thermal equilibrium, emits a characteristic distribution of wavelengths at a specific temperature |
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Explanation for microwave background radiation |
Universe was originally saturated with gamma photons, as the universe expanded space was stretched and so was the wavelength of the photons Universe started out hot but cooled over time to 2.7k today. At this temperature it can be modelled as a black body with microwave peak wavelength |
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The cosmological principle |
The assumption that, when viewed on a large enough scale, the Universe is homogenous, isotropic and the laws of Physics are universal |
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Meaning of Homogenous |
The density of matter throughout the Universe is uniform |
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Meaning of isotropic |
The Universe looks the same in every direction to any observer in the Universe (there is no centre or edge to the universe) |
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Equation for specific latent heat |
L = E / m Where E = energy supplied and m = mass |
