Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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Workshop 5

4. Burning

cashews burningCombustion—the process by which things burn—is chemically identical to respiration. In both processes oxygen reacts with carbon-based substances, releasing energy. The primary differences lie in how and in what forms the energy is released.

  • Combustion is relatively fast and can be controlled only by the amount of fuel and oxygen available. The energy products of combustion are light and heat, which can be intense. Some of the heat of combustion can be converted to other forms, such as mechanical motion (as in a steam engine). Carbon dioxide is a major product of combustion.
  • Respiration is relatively slow and controlled. The energy products of respiration include heat and the fuel for life processes, including growth, reproduction, and movement. The heat of respiration must be maintained within strict limits if it is not to damage the living tissues within which it occurs. As with combustion, carbon dioxide is a major product of respiration.
Just about any compound with carbon will combust. Complex compounds like carbohydrates, fats, and proteins will burn, as any careless cook knows. However, only simple carbon-containing substances can take part in respiration. The chemical equations for combustion and for respiration are identical.

Combustion of a carbohydrate
(CH2O) + O2 -> CO2 + H2O + Energy (Heat and Light)

Respiration of a carbohydrate
(CH2O) + O2 -> CO2 + H2O + Energy (Heat and Fuel for Life Processes.)


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