Week 6: Thermal Physics :check: (Temperature is a measure of the average…
Week 6: Thermal Physics :check:
Temperature is a measure of the average kinetic energy of the particles.
S.I unit of temperature is Kelvin, K
Other possible temperature scales are: degree Celsius (oC), degree Fahrenheit (oF)
K = oC + 273.15
(average..Particles) affects the arrangement of the particles
in Kinetic Theory of Matter: matter is composed of a large number of small particles—individual atoms or molecules—that are in constant motion.
Heat/ Thermal energy is energy itself
S.I Unit for heat is Joule, J
Also can be expressed in in calories, cal.
Absolute zero 9-273 Celsius): A point where an object cannot get any colder. At this temperature, molecules do not have any kinetic energy because they have stopped moving.
Has no upper bound; there is no limit to how hot an object can get
Zeroth law of thermodynamics: If A and B are in thermal equilibrium, they transfer no net heat between each other.
If A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then B and C are in thermal equilibrium with each other.
Thermal equilibrium: no interaction between the tea and thermometer and hence no further change in the temperature of any part of the system.
Heat Transfer with particles gaining/losing kinetic energy that changes temperature or phase
Three modes of heat transfer
Radiation: a form of energy transport consisting of electromagnetic waves traveling at the speed of light.
Includes Thermal radiation (often called infrared radiation): a type electromagnetic radiation (or light).
does not rely upon any contact between the heat source and the heated object.
No mass is exchanged and no medium is required.
objects that radiate heat more efficiently, also absorb heat more efficiently.
(Eg) Black & Matte objects are better radiators & absorbents of heat unlike sliver & shiny objects
Conduction: In solids, particles vibrate about their fixed positions and “hit” particles next to them to transfer some energy to those particles
repeats and creates a transfer of energy within the material.
In metals the electrons can move freely, hence kinetic energy can be transferred very quickly (THUS they are good conductors of heat)
Convection: In fluids, transfer of heat from one part of a fluid to another by the movement of the fluid from hotter to the colder part, via convection currents.
(Movement) creates the transfer of energy.
Q = mcT or Q = C T
Q: quantity of heat transferred,
m: mass of the object,
c: specific heat capacity of the object.
quantity of heat required to raise the temperature of the 1kg of the object by 1 degree. SI unit is joule per Kelvin per kg (J/(K.kg)
C: heat capacity of the object
quantity of heat required to raise the temperature of the object by 1 degree. SI unit is joule per Kelvin (J/K).
Phase from breaking the cohesive bonds between molecules.
Q = mLf or Q = mLv
During a phase change energy is added or subtracted from a system, but the temperature will not change. The temperature will change only when the phase change has completed.
Q: quantity of heat transferred, required to change the phase of a substance
m: mass of the object,
Lf: latent heat of fusion (from solid to liquid)
Lv: latent heat of vaporisation (from liquid to gas)
intensive property measured in units of J/kg, depending on the substance, particularly on the strength of its molecular forces
latent/hidden because in phase changes, energy enters or leaves a system without causing a temperature change in the system; so, in effect, the energy is hidden