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31 Cards in this Set
- Front
- Back
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Combustion Reaction |
Heat + Fuel + O2 ——> Heat + Light + New Products |
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When does Complete Combustion occur? |
When Fuel, O2 and Heat are in perfect ratios (very rare). |
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What is it called when fuel, heat and O2 ratios are not perfect in the combustion reaction? |
Incomplete reaction |
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What incomplete combustion occurs what new products can be created? |
Carbon Monoxide, Hydrogen Cyanide, Ammonia, Solid Particles |
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What are the 3 (general) states of matter? |
Solid — Liquid — Gas |
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What is pyrolysis? |
The chemical decomposition of a substance when heat is applied. |
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What is created when pyrolysis occurs? |
Highly flammable vapours. |
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When more heat is applied to a substance the rate of pyrolysis... |
Increases |
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How does surface area influence how something burns? |
As surface area increases the rate it burns also increases because it will more readily absorb heat, breakdown and ignite. |
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What must occur for liquid to burn? |
They must Vaporise. |
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Flash point is defined as... |
The lowest temperature that a liquid will give off enough flammable vapours to produce a flash on the application of an ignition source but will not continue to burn once the ignition source is removed. |
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Fire Point is defined as... |
The lowest temperature that liquid will give off enough flammable vapours in air to produce a flash on the application of an ignition source and then continue to burn once ignition source has been removed. |
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Specific Gravity is defined as... |
Measure of density of a liquid in comparison to water. Water = 1 |
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Fire Point is generally how many degrees higher than its Flash Point? |
10 |
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Polar Solvents are defined as... |
Flammable liquids that mix with water. |
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If a liquid has a specific gravity less than one it will.... |
Float on water |
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Do gaseous fuels need to change state to burn? |
No |
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Vapour Density is defined as... |
Measure of density of a vapour against air. Air = 1 |
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If a gas has a density less than 1 will it settle in low areas? |
No because it is lighter than air. |
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Flammability Range is defined as... |
For a flammable fuel and air mixture to burn, its concentration must lie between two limits. |
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The 3 flammability range limits are? |
Lower Flammability Limit (LFL) Upper Flammability Limit (UFL) Ideal Mixture |
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The LFL is defined as... |
The minimum concentration of a fuel to air which will support combustion. |
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The UFL is defined as... |
The maximum concentration of fuel to air which will support combustion. |
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Ideal Mixture if defined as... |
A point between the LFL and UFL which has the ideal proportions of fuel to air. |
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A mixture with too much fuel to air is know as ‘too rich’ or ‘too lean’? |
Too Rich |
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What happens to the LFL and UFL when temperature is increased? |
They both widen. |
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What happens to the LFL and UFL in areas with enriched Oxygen concentration? |
The LFL remains steady and the UFL will increase. Therefore increasing the flammability range. |
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The 3 types of heat transfer are? |
Convection - transfer of heat through movement of air or liquid. Conduction - heat transfer through a solid by the collision of molecules. Radiation - heat transfer through electromagnetic waves. |
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3 stages of Fire Development are... |
1) Growth - once flaming combustion occurs and the fire has sufficient fuel and oxygen available. 2) Fully Developed - the fire has developed as far as the fuel and oxygen supply will allow. 3) Decay - slowing of combustion due the consumption of available fuel. |
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How can fires be extinguished? |
Removal of one or more elements of the fire tetrahedron. Heat Fuel Oxygen Chemical Chain Reaction |
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Taking away one or more elements of the fire tetrahedron can be achieved by: |
Cool - removal of HEAT Starve - removal or separation of unburnt FUEL Smother - remove/dilute OXYGEN supply Inhibiting the Chemical Chain Reaction at a chemical level e.g. Dry Chem Powder. |
