Thermodynamics

• The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another.
• The first law of thermodynamics states that energy cannot be created or destroyed, only transferred.
• Entropy is a measure of wasted heat energy or unusable energy.
• According to the second law, entropy always increases as a result of the natural tendency of things to move towards disorder and randomness.
• Heat is the transfer of thermal energy from one object to another due to a temperature difference between them.
• Plasma is made up of charged particles, making it different from gases
• Heat is a form of kinetic energy
• Thermal equilibrium is reached when heat transfers until substances in contact have the same temperature
• Temperature is a measure of the average kinetic energy of a substance
• Solids:

  • are not stationary due to vibration of particles
  • More energy leads to more movement of particles and they come apart
  • Have a fixed shape and are held in place by attractive and repulsive forces
• Liquids:

  • Balanced by attractive and repulsion forces
  • Have more freedom, can take shape, and flow
  • Generally have a volume slightly larger than solids as they are not ordered rigidly into a lattice
  • Particles collide but remain attracted so volume doesn't change
• Gases:

  • Can be compressed
  • Spread over the entire containment, with concentration weakening as it spreads
  • Particles are in constant random motion, colliding with each other and the container walls
  • Particles move fast enough that collisions and bouncing apart are stronger than the attractive forces
• Kinetic particle model:

  • States that all matter is made of small particles in constant motion
  • Involves collisions between particles where the total kinetic energy before and after collision remains the same
  • Includes both repulsion and attraction between particles
• Kinetic particle model and temperature:

  • Temperature is a measure of the average kinetic energy of a substance based on the kinetic particle model
  • Higher temperature equals higher average kinetic energy
  • Adding energy as thermal energy increases the average thermal energy
  • Heat always flows from hot to cold
• Temperature measures:

  • Arbitrary scales like Fahrenheit and Celsius have fixed points chosen randomly
  • Absolute temperature scale is Kelvin, which cannot have negative values and is always 273 more than Celsius (0°C + 273 = Kelvin)
• Internal kinetic energy:

  • Due to the motion of particles
  • Directly related to temperature, with higher temperature leading to higher kinetic energy
  • The vigor of movement depends on whether bonds start to break
• Internal energy:

  • Related to kinetic energy and potential energy of a substance
  • Total energy in a substance, including kinetic energy (movement of particles) and potential energy (bonds that are stretched and compressed)
  • A substance with internal energy can transfer energy to its environment
• Internal potential energy:

  • Stores potential energy due to stretching and compression of bonds as particles move
  • Amount of potential energy depends on forces between particles and their distance apart
  • Energy stored in bonds between particles
• Energy efficiency (𝓷):

  • Represents the efficiency of energy transfers, where not all energy ends up where intended
  • Thermal energy is a common waste energy as heat is sometimes undesired
• Work and heat:

  • When an object transfers energy, it does work
  • If an object receives energy, work has been done to it
  • Total internal energy increases if work is done on an object or heat flows into it, and it decreases if work is done by the object or heat is lost
  • Equation: ΔU = Q + W
• Power:

  • Describes the energy transferred per second
  • Heat is sometimes described as energy per second (measured in Watts)
• Latent heat:

  • The energy required for a substance to change state
  • Amount of energy transferred for 1kg of a substance to solidify or melt
  • Energy is absorbed when melting and released when solidifying
• Thermal equilibrium:

  • Loss of energy is equal to gain
• Conduction:

  • Heat transfer within solids through physical collisions between particles
• Convection:

  • Heat transfer within fluids (liquids and gases) due to fluid movement
• Radiation:

  • Heat transfer through photons of electromagnetic waves
• Phase changes use potential energy, while heat changes use kinetic energy
• Heat:

  • Flow of thermal energy between objects due to temperature differences
  • Objects can gain or lose heat but cannot have heat
• Specific heat capacity:

  • Amount of heat/energy required to raise the temperature of 1kg of a substance by one degree Celsius
• Equation for finding heat addition or removal:

  • Q = mcΔT
• Example question:

  • Problem: A 50g sample of copper at 25°C has 1200J of thermal energy added, what is the final temperature?
  • Solution: ΔT = 1200 / (0.05 × 385) = 62.0°C, Final temperature = 25.0°C + 62.0°C = 87.0°C
• Energy and change of state:

  • Energy is constantly added during state changes, even when temperature remains constant
  • Energy goes into changing the state of the substance
• Thermal energy transfers:

  • All forms allow for an increase in kinetic energy of particles in a body