Thermal Physics Flashcards
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Thermal Equilibrium
Two substances in physical contact with each other no longer exchange any heat energy and both reach an equal temperature. There is no longer thermal energy transfer between the regions
Triple Point
The temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium
Zeroth Law
this law states if two objects are each in thermal equilibrium with a third, then all three are in thermal equilibrium with each other.
Absolute scale of temperature
This can be also called the thermodynamic temperature scale which uses the triple point of pure water and absolute zero as its fixed points
absolute zero
the lowest possible temperature (-273 degrees/0K) where KE is zero and volume and pressure of gas are 0. The internal energy is minimum but not 0 because it still has electrostatic potential energy stored between the particles
SI base unit of temperature
Kelvin (T= theta + 273)
Kinetic Model
This describes how all substances are made up of atoms or molecules which are arranged differently depending on the phase of the substance
brownian motion
random motion of smoke particles visible under a microscope
Internal energy
the sum of randomly distributed kinetic and potential energies of atoms or molecules within the substance
How the internal energy of a body will increase
increasing the temperature will increases the average kinetic energy of the molecules or atoms inside the body
what factors affect internal energy
- temperature
- change of state (solid to liquid, electrostatic potential energy increases)
Electrostatic potential energies at different phases of a substance?
GAS- electrostatic potential energy is 0 as there are no negligible electrical forces between atoms or molecules
LIQUID- the electrostatic forces between atoms or molecules give the electrostatic potential a negative value. this means energy must be supplied to break the bonds
SOLID- the electrostatic forces between atoms or molecules are very large, so electrostatic potential energy has a large negative value
what happens to temperature during change of phase
Temperature is constant
specific heat capacity
energy required per unit mass to change the temperature by 1K
equation for specific heat capacity
c=E/M*(change in temperature)
Determing specific heat capacity
simple experiment using an electrical heater can be used to determine c of a solid or a liquid. The energy transfered from the heater to the substance is given by E=IVt (I is the current in the heater, V is the potential difference across the heater and t is the time taken to increase the temperature). so C=IVt/M(change in temperature). plot on graph temperature against time and the specific heat capacity is equal to p/mgradient
specific latent heat of a substance
the energy require to change the phase per unit mass while at a constant temperature (L=E/m)
specific latent heat of fusion
the energy required for the substance to change from solid to liquid
specific latent heat of fusion method explantion
-substance at its melting point requires energy to change phase from solid to liquid
-the energy transfered to the substance increases the internal energy of substance with temperature staying constant
specific latent heat of vaporisation
the energy required for the substance to change state from liquid to gas
experiment to determine the latent heat of fusion
- heating circuit to be used
- thermometer to be used to ensure ice is at its melting point and ice should not be melting until the heater is switched on
- measure the potential difference across the heater, the current in the heater and the time during which the heater is used. energy transfered to the ice from the heater is equal to VIt
- measure the mass of the substance
Latent heat of fusion=IVt/m
experiment to measure the latent heat of vaporistaion
- electric heater to be used with a condenser to collect and then measure the mass of liquid that changes phase
-=IVt/m
