THERMODYNAMICS (Part I)
ENERGY
Energy has no mass or volume
By measuring changes in temperature we can measure the change in somethingโs energy content
Wood burns because trees gather sunlight, water, and carbon dioxide. This gathered potential
energy can be released as chemical energy.
Sunlight is the source of the chemical energy stored in all substances we consume as food and
fuel.
Nearly all chemical reactions and all physical changes of matter involve changes in energy.
When hydrogen combines with oxygen to form water, it releases energy that can be converted
into motion (spacecraft lifting off) or electric energy (fuel cells)
Thermodynamics โ The study of energy and its transformations
Thermochemistry โ The study of the relation between chemical reactions and changes in energy
Thermochemical equation โ An equation of a reaction in which energy is either in the reactant or
product (absorbed or released)
Energy โ The capacity to do work or transfer heat.
Heat โ The energy transferred between objects because of their temperatures
Work โ A form of energy; the energy required to move an object through a given distance
Heat transfer โ The process of heat energy flowing from one object into another.
(Heat always flows from hotter objects to cooler objects)
Thermal equilibrium โ A condition in which temperature is constant throughout the material and
no heat flows from one point to the other.
Work is done whenever a force moves an object through a distance: w = F x d
Potential energy โ The energy stored in an object because of its position.
State function โ A property of an entity based solely its chemical and/or physical state, but not
how it achieved that state (Potential Energy)
Kinetic Energy โ The energy of an object in motion due to its mass (m) and its speed (u) (KE =
1/2mu2)
Law of conservation of energy โ Energy cannot be created or destroyed (though it can be
converted)
Total energy at any position is the sum of Potential + Kinetic Energy
SYSTEM, SURROUNDINGS, AND ENERGY TRANSFER
System โ The part of the universe that is the focus of a thermochemical study.
Surrounding โ Everything that is not part of the system
