Thermal Physics Flashcards
What is heat?
Heat is thermal energy transferred from higher to lower temperature due to temperature difference
When will net transfer of thermal energy stop?
When both object reaches thermal equilibrium, eg. same temperature
When are two object in thermal equilibrium?
If they have same temperature and no net heat transfer between them
What is temperature?
- scalar base quantity that is proportional to the average KE of a substance
- a property that determines whether an object is in thermal equilibrium with other objects
Is temperature the measure of the amount of thermal energy in a body?
- no
- different heat capacity of object
- temperature shows direction of thermal energy transfer
What is the 0th law of thermodynamics?
If an object A and object B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each other
What is absolute scale?
thermodynamic temperature scale that does not depend on thermometric properties of any substance
What is absolute zero?
- Lowest limit of thermodynamic temperature scale
- a state at which the enthalpy and entropy change of a cooled ideal gas reach its minimum value, taken as zero kelvin
What is the triple point of water?
- temperature and pressure at which three phases (gas, liquid and solid) of that substance coexist in thermal equilibrium
- temperature and pressure at which sublimation curve, fusion curve and vapourisation curve meet
- 273.16K (0.01 degree celsius)
What is one kelvin?
1/273.16 of the thermodynamic temperature of the triple point of pure water
What is Boyle’s Law?
Pressure of a fixed mass of ideal gas at constant temperature is inversely proportional to its volume
What is Charles’ law?
Volume of a fixed mass of ideal gas at constant pressure is directly proportional to its thermodynamic temperature
What is pressure law?
Pressure of a fixed mass of ideal gas at constant volume is directly proportional to its thermodynamic temperature
What is ideal gas?
a gas which obeys pV=nRT, where p is the pressure of the gas, V is the volume of the gas, n is the total number of moles of gas, T is thermodynamic temperature of the gas
What are the assumptions for kinetic theory of gases and molecules?
- collisions between molecules and container are perfectly elastic
- molecules do not exert any intermolecular forces on one another
- time during collisions is negligible compared to time between collisions
- volume of molecules is negligble as comapred to volume occupied by the gas
- molecules are in rapid, random motion
- molecules of gas are hard, identical spheres
- average separation between molecules are large compared to size of molecules
What happens during boiling?
- liquid to gas
- bonds between molecules are broken completely and external work is done against atmosphere
- temperature remains constant
What happens during melting?
- solid to liquid
- bonds betwen molecules are weakened so lattice structure collapse
- temperature remains constant
What is the relationship between external pressure and boiling point?
The higher the external pressure, the higher the boiling point
(more work needs to be done against atmosphere)
What is the relationship between external pressure and melting point?
The higher the external pressure, the lower the melting point
(more work is done on the object)
What is the latent heat of vapourisation?
Energy supplied during boiling or energy released during condensation
What is latent heat of fusion?
Energy supplied during melting or energy released during freezing
What is evaporisation?
- type of vaporisation that occurs on surface of liquid as it changes into gas phase
- bonds between molecules are broken and external work is done against atmosphere
What is heat capacity, C?
amount of thermal energy required to raise the temperature of a substance by 1K
What is specific heat capacity?
amount of thermal energy required to raise temperature of a unit mass of substance by 1K
What is latent heat?
Energy released or absorbed by a substance during a change of state, without a change in its temperature
What is specific latent heat of fusion?
Amount of thermal energy required to change unit mass of a substance from solid to liquid state, without a change in its temperature
What is specific latent heat of vapourisation?
amount of thermal energy required to change unit mass of the substance from liquid to gaseous state, without a change in its temperature
What is internal energy?
Sum of microscopic kinetic energies due to random motion and microscopic potential energies due to intermolecular forces of attraction of all molecules in the system
What is the first law of thermodynamics?
The increase in internal energy of a system is equal to the sum of heat supplied and work done on the system
When does isothermal process occur?
When change of volume and pressure takes place without a change in temperature
What is special about the change in internal energy of ideal gas?
- change in internal energy depends on change of temperature
- U = KE, KE depends on T
When does isometric/isochoric process occur?
Change in temperature and pressure without a change in volume
When does isobaric process occur?
Change of temperature and volume occur without a change in pressure
When does an adiabatic process occur?
When the change of volume, pressure and temperature occur with no heat supplied or lost from the system (Q = 0)
What does going back to same point of the pV curve mean?
Change in internal energy is 0
What is the area under pV curve?
Work done
What is one mole?
Amount containing 6.02 * 10^23 mol of particles
What is the relationship between the kinetic energy of ideal gas and temperature?
Mean kinetic energy of a molecule of an ideal gas is proportional to thermodynamic temperature
What is used to calibrate Kelvin scale?
absolute zero and triple point of water used to calibrate scale
