Endothermic Reaction
A chemical reaction in which a substance absorbs energy as it occurs.
Example: spraying water on a fire; the water absorbs the heat and then converts from a liquid to a gas, making steam
endo = enter/absorb
thermic = heat (energy)
absorbing heat (energy)
Exothermic Reaction
A chemical reaction between two or more substances that gives off energy as it occurs.
Example: oxygen, fuel and heat react together to form fire, which then gives of energy in the form of heat, light and toxic smoke
exo = exit
thermic = heat (energy)
Exi
Physical Change
occurs when a substance remains chemically the same but changes in size, shape or appearance.
Example: water freezing - liquid to solid
Example: water boiling - liquid to gas
Chemical Reaction
occurs when a substance changes from one type of matter into another
Chemical Change
Often involves the reaction of two or more substances to form other types of compounds
Matter
Anything that occupies space and mass
Oxidation
A chemical reaction involving the combination of oxygen with other materials causing it to break down and lose elements.
Example: It cam be slow, such as the combination of oxygen with iron to from rust
Example: It can be rapid as in combustion of methane
21%
Our atmosphere is composed of _____ percent oxygen
Combustion
An exothermic chemical reaction that is a self-sustaining process of rapid oxidation of a fuel that produces heat and light
Fire Triangle
Oxygen, fuel and heat.
Remove any one of these components and fire cannot start and if burning it will be extinguished.
A nonflaming or smoldering combustion
Fire Tetrahedron
Oxygen, fuel, heat and a self-sustaining chemical chain reaction. A flaming combustion
Potential Energy
Stored energy possessed by an object that can be released in the future
Example: Before ignition, a fuel has potential chemical energy to burn
Kinetic Energy
The energy possessed by a moving object
Example: Heat is kinetic energy associated with the movement of atoms and molecules that comprise matter
Joules
A measurement for heat energy using the International System of Units or metric system
A Joule is equal to 1 newton over a distance of 1 meter
British Thermal Units - BTU's
A measurement for heat energy using the Customary System
The British Thermal Unit is the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit
Heat
Heat is a form of energy
Heat is kinetic energy associated with the movement of the atoms and molecules that comprise matter
Heat energy will move from objects of higher temperature to those of lower temperature
Temperature
Temperature is a measurement of kinetic energy
There are several different scales used to measure temperature but the most common are the Celsius and Fahrenheit scales
The Celsius temperature scale uses the metric system
- Boiling Point - 100?
- Room Temp
Work
Energy is the capacity to perform work
Work occurs when a force is applied to an object over a distance or when a chemical, biological or physical transformation is made in a substance.
Pyrolysis
the chemical decomposition of a substance through the action of heat
Ignition
There are two forms of ignition:
Piloted Ignition - when a mixture of fuel and oxygen encounter an external heat source with sufficient heat energy to start the combustion reaction
Autoignition - ignition that occurs when a substance is heated sufficientl
Autoignition Temperature (AIT)
The temperature at which autoignition occurs
Sources of Heat Energy
- Chemical
- Mechanical
- Electrical
- Light
- Nuclear
- Sound
Chemical, Mechanical and Electrical energy are common sources of heat that result in the ignition of fuel
Chemical Heat Energy
Heat produced from a chemical reaction including combustion, spontaneous heating, heat of decomposition and heat of solution
Chemical Heat Energy is the most common source of heat in combustion reactions.
Electrical Heat Energy
Electrical Heat Energy can generate temperatures high enough to ignite any combustible material near the heated area. Electrical Heat can occur I several ways:
Resistance Heating - Heat generated by passing an electrical current through a conductor such a
Mechanical Heat Energy
Mechanical Heat Energy is generated by friction or compression.
The movement of two surfaces against each other creates heat of friction.
Heat of compression is generated when a gas is compressed
Transmission of Heat
Heat moves from warmer objects to those that are cooler. The rate at which heat is transferred is related to the temperature differential of the bodies and the thermal conductivity of the material involved. For any given substance, the greater the tempera