D

Physics: Heat Transfer and Thermodynamics Notes (copy) (copy) (copy) (copy) (copy) (copy) (copy) (copy) (copy) (copy) (copy)

Physics: Heat Transfer and Thermodynamics Notes

Measurement Scales

  • Celsius Scale - based on where water freezes and where water boils

  • Kelvin scale - based on the movement of particles

Absolute Zero 

  • Occurs at 0 K where all particles stop moving

  • It is not possible for temperatures to go below 0 K

  • 0 K equates to -273.15 degrees celsius

Particle Motion

  • Hot Air = fast particle motion

  • Cold Air = slow particle motion

Thermal Expansion

  • Fast moving particles spread out

  • Causes objects to expand when heated and to contract when cooled

  • Different materials have different rates of expansion and contraction

Kinetic Energy

  • Kinetic Energy - energy associated with the movement of molecules

  • Heat energy is transferred from one object to another

  • Kinetic - Molecular Theory - when particles move faster kinetic energy and temperature both increases

Heat Flow in Substancs

  • Energy travels from high energy to low energy

  • High energy = hot

  • Low energy = cold

Conduction

  • Energy transferred through direct contact

  • When materials are heated electron gain energy causing them to move faster

  • When electrons collide, energy is transferred to nearby electrons

Convection

  • Energy transferred through the mixing of fluids

  • Hot fluid rises while cold fluid sinks

  • Heat occurs due to a movement with fluids

Radiation

  • Energy transferred by the emission of electromagnetic waves

Specific Heat

  • Refers to the specific amount of energy needed to raise the temperature of a certain materual

  • A material with a low specific heat changed temperature more easily

Heat Formula

  • Heat formula - Q=mcΔT

  • Q = heat (joules)

  • m = mass (kg)

  • c = specific heat

  • ΔT = change in temperature

Heat

  • If heat (Q) is negative heat has been lossed therefore temperature decreases

  • If heat (Q) is positive heat has been gained therefore temperature increases

Law of Conservation

  • The total amount of energy always remains the same

  • The amount of energy loses by one object is gained by another

Conductors and Insulators

  • Conductors examples - metals, water

  • Insulators examples - insulation, foam, air

Kinetic and Potential energy

  • Kinetic energy - associated with movement

  • Potential energy - stored energy, can also be chemical

Thermal Equilibrium

  • Occurs when no more energy or heat cn be transferred

  • Occurs when two objects have reached the same temperature

Thermodynamics

  • Study of heat and its transformation to mechanical energy

Four Laws to Thermodynamics

  • Zeroth Law

  • 1st Law

  • 2nd Law

  • 3rd Law

Zeroth Law of Thermodynamics

  • This law states if two objects are in an equilibrium with a third object then they are all in an equilibrium with each other

First Law of Thermodynamics

  • This law states that if the total increase in thermal energy of a system equals to the sum of the heat added to it

  • energy is conserved

Entropy

  • entropy - measure of disorder in a system

  • solids have lower entropy while gasses have higher

Second Law of Thermodynamics

  • This law states that entropy of the universe is always maintained or increasing

  • it is impossible for any device to be 100% efficient

Third Law of Thermodynamics

  • This law states that entropy decreases as temperature decreases

  • Entropy is close to absolute zero

  • As temperatures increases so does entropy causing particles to move faster