Glossary
Adiabatic Process
A thermodynamic process in which no heat is exchanged between the system and its surroundings. This occurs either very rapidly or within a perfectly insulated system.
Example:
The rapid compression of air in a diesel engine cylinder is an Adiabatic Process, causing the air to heat up significantly without external heat input.
Boundary (Thermodynamic)
The real or imaginary surface that separates a thermodynamic system from its surroundings. It can be fixed or movable, permeable or impermeable.
Example:
The walls of a pressure cooker act as the Boundary separating the steam inside from the kitchen air outside.
Closed System
A system that can exchange energy (heat and work) but not matter with its surroundings. Its total mass remains constant.
Example:
A sealed can of soda is a Closed System because it can get colder (lose heat) but no soda can escape.
Conduction
The transfer of heat through direct molecular collision within a material or between materials in direct contact, without any bulk movement of the material itself.
Example:
If you hold one end of a metal rod in a flame, the other end eventually gets hot due to Conduction.
Conservation of Momentum
A fundamental principle stating that the total momentum of an isolated system remains constant if no external forces act on it. This applies to both elastic and inelastic collisions.
Example:
When a rocket expels exhaust gases, the Conservation of Momentum dictates that the rocket moves in the opposite direction.
Contact Forces (in Thermodynamics)
Forces that occur when two objects are in direct physical contact, such as normal force, friction, or the force exerted by a fluid on a surface.
Example:
The Contact Forces between a hot pan and a stovetop burner allow heat to transfer via conduction.
Convection
The transfer of heat through the movement of fluids (liquids or gases). Warmer, less dense fluid rises, and cooler, denser fluid sinks, creating a current.
Example:
Boiling water in a pot demonstrates Convection as hot water rises and cooler water sinks, creating a circulating current.
Elastic Collisions
Collisions in which both kinetic energy and momentum are conserved. Objects bounce off each other without any loss of kinetic energy to other forms.
Example:
The collision of two billiard balls is a close approximation of an Elastic Collision, where kinetic energy is largely conserved.
Electromagnetic Forces (in Thermodynamics)
Forces arising from electric and magnetic properties of matter, which can affect the internal energy of a system and contribute to work done, particularly in systems involving charged particles or fields.
Example:
The Electromagnetic Forces within a battery drive the chemical reactions that release energy, which can then do work.
Energy Transfer
The movement of energy from one system or object to another, or from one form to another. This can occur as heat, work, or other mechanisms.
Example:
When you rub your hands together, the mechanical energy of friction results in Energy Transfer as heat to your skin.
Entropy
A thermodynamic property that measures the disorder, randomness, or unavailability of a system's thermal energy for conversion into mechanical work. It tends to increase in isolated systems.
Example:
When an ice cube melts in a glass of water, the system's Entropy increases as the highly ordered ice turns into disordered liquid water.
First Law of Thermodynamics
A statement of the conservation of energy, stating that the change in a system's internal energy equals the heat added to the system minus the work done by the system (ΔU = Q - W).
Example:
When a balloon is inflated, the First Law of Thermodynamics explains how the work done on the gas and any heat exchange affect its internal energy.
Free-Body Diagrams (in Thermodynamics)
Diagrams used to visualize and analyze all external forces acting on a specific object or part of a thermodynamic system, aiding in understanding mechanical interactions.
Example:
Drawing a Free-Body Diagram of a piston in an engine helps determine the net force acting on it due to gas pressure and external loads.
Gravitational Forces (in Thermodynamics)
Forces related to mass and distance, which can influence fluid behavior and pressure distribution within a thermodynamic system, especially in large-scale systems like atmospheres.
Example:
The Gravitational Forces acting on air molecules contribute to the atmospheric pressure at different altitudes.
Heat
The transfer of thermal energy between systems due to a temperature difference. It flows from a region of higher temperature to a region of lower temperature.
Example:
When you place a cold spoon into hot soup, Heat flows from the soup to the spoon, warming the spoon.
Heat Transfer
The process by which thermal energy moves from one place to another. The primary mechanisms are conduction, convection, and radiation.
Example:
The warmth you feel from a campfire is due to Heat Transfer primarily through radiation.
Ideal Gas Law
A fundamental equation that describes the behavior of an ideal gas, relating its pressure (P), volume (V), number of moles (n), and temperature (T) as PV = nRT.
Example:
Using the Ideal Gas Law, you can calculate how much the pressure inside a balloon will increase if its temperature rises.
Inelastic Collisions
Collisions in which kinetic energy is not conserved, although momentum is still conserved. Some kinetic energy is converted into other forms, such as heat, sound, or deformation.
Example:
A car crash is an Inelastic Collision because kinetic energy is lost to sound, heat, and the deformation of the vehicles.
Internal Energy
The total energy contained within a thermodynamic system, comprising the kinetic and potential energies of its constituent particles. It can be changed by heat or work.
Example:
Heating a gas increases its Internal Energy, causing its molecules to move faster.
Isobaric Process
A thermodynamic process during which the pressure of the system remains constant. Changes in volume and temperature occur while maintaining constant pressure.
Example:
Heating a gas in a cylinder with a movable piston that is free to move against constant atmospheric pressure represents an Isobaric Process.
Isolated System
A system that exchanges neither matter nor energy with its surroundings. Its total energy and mass remain constant.
Example:
A perfectly insulated thermos containing hot coffee, if such a thing existed, would be an Isolated System.
Isothermal Process
A thermodynamic process during which the temperature of the system remains constant. Any heat added or removed is balanced by work done by or on the system.
Example:
When a gas expands slowly in contact with a large heat reservoir, it undergoes an Isothermal Process, maintaining a constant temperature.
Open System
A system that can exchange both matter and energy with its surroundings. Its mass and energy content can change.
Example:
A boiling pot of water without a lid is an Open System as both steam (matter) and heat (energy) escape into the air.
Pressure
The force exerted perpendicularly per unit area on a surface. It is a fundamental property in analyzing thermodynamic processes.
Example:
The Pressure inside a bicycle tire increases as more air is pumped in, exerting a greater force on the inner walls.
Pressure Forces
Forces exerted by fluids on the walls of their containers or on submerged objects, arising from the collisions of fluid particles with the surfaces.
Example:
The Pressure Forces exerted by steam inside a turbine push the blades, causing them to rotate and generate electricity.
Probability (in Thermodynamics)
The likelihood of a particular arrangement or state of particles within a system. In thermodynamics, systems tend towards states with higher probability, corresponding to greater disorder.
Example:
The Probability of all air molecules in a room spontaneously gathering in one corner is extremely low, reflecting the natural tendency towards uniform distribution.
Radiation
The transfer of heat through electromagnetic waves, which does not require a medium. It can occur through a vacuum.
Example:
The warmth you feel from the sun on your skin is primarily due to Radiation.
Second Law of Thermodynamics
States that the total entropy of an isolated system can only increase over time, or remain constant in ideal cases. It implies that natural processes tend towards greater disorder.
Example:
The Second Law of Thermodynamics explains why a broken glass cannot spontaneously reassemble itself; the process would decrease the system's entropy.
Surroundings
Everything external to the thermodynamic system that can interact with it by exchanging energy or matter.
Example:
For a cup of hot coffee, the air in the room and the cup itself are part of the Surroundings.
System (Thermodynamic)
A specific region or quantity of matter chosen for study in thermodynamics. It is separated from its surroundings by a defined boundary.
Example:
When analyzing a refrigerator, the refrigerant circulating inside is considered the System.
Temperature
A measure of the average kinetic energy of the particles within a substance. It indicates the degree of hotness or coldness of an object.
Example:
The Temperature of boiling water is 100 degrees Celsius, indicating its molecules have a high average kinetic energy.
The Carnot Cycle
A theoretical thermodynamic cycle that describes the most efficient possible heat engine. It consists of two isothermal and two adiabatic processes.
Example:
Engineers use the principles of The Carnot Cycle to set theoretical limits on the maximum efficiency achievable by real-world heat engines.
Thermal Conductivity
A material property that quantifies its ability to conduct heat. Materials with high thermal conductivity transfer heat efficiently, while those with low conductivity are good insulators.
Example:
Copper has high Thermal Conductivity, which is why it's used in cooking pots to quickly transfer heat to food.
Thermal Equilibrium
A state where two or more systems in thermal contact have reached the same temperature, resulting in no net heat transfer between them.
Example:
When a cold drink sits out on a table, it eventually reaches Thermal Equilibrium with the room, becoming room temperature.
Thermodynamics
The branch of physics that deals with heat and its relation to other forms of energy and work. It describes how energy is transferred and transformed within systems.
Example:
Studying the efficiency of a car engine involves applying principles of Thermodynamics to understand how fuel energy is converted into mechanical work.
Transformations (Energy)
The process by which energy changes from one form to another, such as chemical energy to thermal energy or electrical energy to light energy.
Example:
A solar panel performs an energy Transformation, converting light energy from the sun into electrical energy.
Work (Thermodynamic)
Energy transferred when a force causes displacement. In thermodynamics, it often refers to energy transferred by a system expanding or compressing against an external pressure.
Example:
A gas expanding in a cylinder pushes a piston, doing Work on the surroundings.