# 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

• 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