# Definitions Thermal physics

### Description

Physics (Thermal physics) Flashcards on Definitions Thermal physics, created by Moa Lindström on 04/05/2014.
Flashcards by Moa Lindström, updated more than 1 year ago
 Created by Moa Lindström about 10 years ago
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## Resource summary

 Question Answer Element material made up of just one type of atom Molecule contains more than one type of atom Compounds materials made from molecules Gas no fixed shape or volume. (ideally) no force between molecules Liquid no fixed shape but fixed volume. force between molecules not so strong so molecules can move around Solid fixed shape and volume. molecules held in position by a force, vibrate but don't move around Temperature (T) a measure of how hot or cold an object is. it is temperature that determines the direction of heat flow Celsius --> Kelvin add 273 Kelvin --> Celsius subtract 273 Thermal capacity (C) the amount of heat needed to raise its (somethings) temperature by 1*C. (J*C^-1) C=Q/(change in)T, where Q is quantity of heat Specific heat capacity (c) the amount of heat required to raise the temperature of 1kg of the material by 1*C. (unit: J kg^-1 *C^-1). c=Q/m(change in)T Boiling takes place throughout the liquid and always at the same temperature Evaporation takes place only at the surface of the liquid and can happen at all temperatures Specific latent heat (L) amount of heat required to change the state of 1kg of the material without change of temperature. L=Q/m (unit: J kg^-1) (latent = hidden) Energy supplied power x time The ideal gas made up of a large number of perfectly ELASTIC, (IDENTICAL) TINY SPHERES moving in random motion. there are no forces between molecules (except when they collide);they move with constant velocity between collisions Pressure force/area Equation of state for an ideal gas PV=nRT. P(ressure), V(olume), n(umber of moles), R (molar gas constant(booklet)), T(emperature) Isobaric constant pressure Isochoric constant volume Isothermal constant temperature Internal energy the sum of all the KE of all the molecules Work done work is done when the point of application of a force moves in the direction of the force. force exerted on piston = PxA. work done when piston is moved (change in) d(istance), work done=PxAx(change in)d -> Ax(change in)d=change in volume V -> work done = Px(change in)V Sign of work + when a gas does work it is pushing the piston out = positive. - if work is done on the gas then something must be pushing the piston in = negative First law of thermodynamics simple version; if a gas expands and gets hot, heat must have been added. according to the law of conservation of energy; Q=(change in)U+W. (Q- amount of heat (change in)U - internal energy, W - work done by gas) Using P(ressure)V(olume) diagrams ~change in VOLUME tells us whether work is done by the gas or on it. ~change in TEMPERATURE tells us whether the internal energy goes up or down. ~change in pressure is not interesting... Adiabatic contraction an adiabatic transformation is one where no heat is exchanged (Q=0). steeper than a "normal" temperature curve. first law of thermodynamics; Q=(change in)U+W -> 0=(change in)U+W -> (change in)U=W Net work done (thermodynamic cycles) the net work done during a (thermodynamic) cycle is the difference between the work done BY the gas and the work done ON the gas. this is equal to the area enclosed by the cycle on a PV diagram Thermodynamic cycle isochoric and isobaric changes. (volume and pressure) The Carnot cycle isothermal and adiabatic changes. (temperature) The second law of thermodynamics it is not possible to convert heat completely into work. (since energy always spreads out) Entropy about the spreading out of energy. ~entropy is a measure of how spread out or disordered the energy has become. ~saying entropy has increased implies that the energy has become more spread out. (change of)S=Q/T, unit: J K^-1. S=entropy, Q=quantity of heat, T=temperature Second law of thermodynamics in terms of ENTROPY in any thermodynamic process, the total entropy ALWAYS increases

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