Unit 5 Thermal Energy
- Created by: megan
- Created on: 21-03-13 13:54
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- Thermal Energy
- Temperature
- Kinetic theory- when energy is supplied to an object, the particles take up the energy as kinetic energy.
- When the internal Kinetic energy has been removed, the temperature is at absolute zero.
- Zero Degrees= 273.15 Kelvin.
- Heat Transfer
- More heat= More frequent collisons.Less heat =Slow moving molecules
- The effect of the collisions means that energy is distributed.
- Specific Heat Capacity
- Transferring the same amount of heat energy to two different objects will increase their internal energy the same amount.
- This will not necessarily cause the same rise in temperature
- The effect that transferred heat energy has on the temperature of an object depends on three things : 1.the amount of heat energy transferred 2.The mass of the objects. 3. The specific heat capacity of the objects material.
- Specific Heat capacity= the amount of energy needed to raise the temperature of 1 kg of a particular substance by 1K.
- Materials have different specific heat capacity because their molecular structures are different.
- dE= mc dT
- Transferring the same amount of heat energy to two different objects will increase their internal energy the same amount.
- Internal Energy
- The average kinetic energy of the molecules in a material give it its temperature.
- Each molecule will have potential energy by virtue of its position within the structure of the material. Or relation to other moleucles in the substance.
- internal energy= kinetic energy of every molecule + Potential energy
- The internal energy is randomly distributed across all the molecules
- The maxwell boltzmann Distribution.
- The values of the indicidual velocities of each molecule in a particular sample are varied.
- As they all have the same mass, the kinetic energies are directly dependent on the speeds.
- There are no molecules with zero energy. Only a few molecules have high energies.There is no maximum value for the energy a molecule can have.
- The graph is for one specific temperature. as temperature changes the peak moves towards higher energies.
- Root mean square speed is the speed associated with the average kinetic energy.
- The RMS speed is found by squaring the individual speeds and finding the mean of the squares and then taknig the square root.
- The values of the indicidual velocities of each molecule in a particular sample are varied.
- Molecular Kinetic Energy
- The average kinetic energy of any molecule in a gaseous sample is proportianal to the absolute temperature of the gas
- 1/2 <c ^2> = 3/2 kT
- k= Boltzmann constant = 1.38 x 10 ^-23 JK ^1
- At zero on the absolute scale of temperature the molecules will be stationary.
- The mass cannot change so for their kinetic energy to be zero, at absolute zero their rms speed must also be zero.
- 1/2 <c ^2> = 3/2 kT
- The average kinetic energy of any molecule in a gaseous sample is proportianal to the absolute temperature of the gas
- Gas Laws
- Boyles Law
- For a constant mass of gas at a constant temperaure the pressure exerted by the gas is inversely proportional to the volume it occupies
- Charles Law
- For a constant mass of gas at a constant pressure, the volume occupied by the gas is proportional to its absolute temperature
- The pressure law
- For a constant mass of gas at a constant voume, the pressure exerted by the gas is proportional to its absolute temperature
- Boyles Law
- Ideal Gases
- The gas laws are not perfectly accurate.
- An ideal Gas...
- The molecules have zero size
- The molecules are identical
- The molecules collide with each other except during collisions
- The molecules collide with each other without any loss of energy. in collisions which take zero time
- There are enough molecules so that statistics can be applioed
- An ideal Gas...
- Assuming an ideal gas... PV-NkT
- P= pressure. N= Number of molecules of gass
- Assuming an ideal gas... pv=nRT
- n- the number of moles of gas. R= univeral gass constant = 8.31 jkg^1 mol 61
- The gas laws are not perfectly accurate.
- Temperature
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