Lesson 1: Thermodynamics Part 1

• Thermodynamics


  The study of energy changes in various systems (phase changes, chemical reactions, and nuclear changes)
• Thermochemistry


  The study of energy changes for chemical reactions
• Thermodynamics is very important since every day energy is used in the form of heat (fossil fuels), light (fireflies), mechanical (internal combustion engines) and electrical (batteries) energy
• If the temperatures of the 2 items are close

  The rate of heat exchange will be slower
• Energy

  The capacity to do work or supply heat
• Temperature (T)

  A measure of the average kinetic energy of the particles in a system. Temperature is independent of the amount of material present.
• Kinetic Energy (EK)

  Energy of motion. It results from the movement of particles. The average kinetic energy differs between gases, liquids, and solids of the same substance. EK, (gas) > EK (liquid) > EK (solid)
• Work (w)

  Energy exchanged by mechanical means. Involves the application of a force that is associated with the movement of an object by a specific distance
• Temperature only depends on speed
• Heat (Q)

  Thermal energy that is transferred between objects when a difference in temperature exists. Heat depends on the amount of material that is present.
• Heat is transferred from a hotter object to a colder object


  The temperature of the hotter object will decrease while the temperature of the colder object will increase until both objects reach the same temperature (equilibrium temperature)
• The hotter object originally possesses a greater average Ek than the colder object


  Ek is transferred from the object with greater average Ek to the object with lower average Ek until both have the same average Ek (equilibrium is established)
• A bucket of 50 C water would be better at heating a swimming pool than a cup of 100 C water
• System


  The part of the universe that we choose to study
• Chemical System

  The substance, or group of substances, undergoing change
• Surroundings


  The parts of the universe with which the system interacts (everything in the universe that is not part of our system)
• A system does NOT contain heat or work
• Heat and work are the means by which a system exchanges energy
• Heat and work exist only as changes (ΔT for heat, Δ position for work)
• Internal energy, E

  The total energy contained within a system (substance) = kinetic energy (EK) + potential energy (EP)
• Kinetic energy (EK)

  Energy of motion of the particles
• Potential energy (EP)

  Energy in the form of attractions between atoms/ions (chemical bonds) and between molecules (intermolecular forces)
• The First Law of Thermodynamics

  ΔE = Q + w
• Energy entering a system

  Is associated with a positive sign. If the system absorbs heat then Q>0 (endothermic)
• Energy leaving a system

  Is associated with a negative sign. If the system releases heat, then Q<0 (exothermic)
• The First Law of Thermodynamics arises from The Law of Conservation of Energy
• ΔEuniverse = 0
• Euniverse = Esystem + Esurroundings
• Energy cannot be created or destroyed, only transformed
• In interactions between a system and its surroundings the total energy remains constant
• Energy is neither created nor destroyed, but can be converted from one form to another or transferred between a system and its surroundings
• Qsystem + Qsurroundings = 0
• Qsystem = - Qsurroundings (heat lost = heat gained)
• example of an exothermic reaction:

  Hand warmers, the system (hand warmers) transfer heat to the surroundings (hands), leading to an increase in temperature of the surroundings but a decrease in temperature of the system
• Thermal energy is the total kinetic energy of the particles in an object, directly related to the amount of matter in the object