Chemical Reactions and Energy

• A rise in temperature means an exothermic reaction has occurred
• A decrease in temperature means an endothermic reaction has occurred
• The technical term for burning is combustion
• Anhydrous copper sulphate turns from grey to blue if water is present
• Anhydrous cobalt chloride paper turns from blue to pink if water is present
• When a hydrocarbon or carbohydrate burns, they react with oxygen to produce carbon dioxide and water
• Hydrocarbon- contains hydrogen and carbon only
• Hydrocarbon- contains hydrogen and carbon only

  An example of a hydrocarbon is methane (CH4)
• Carbohydrate- contains carbon, hydrogen and oxygen atoms

  An example of a carbohydrate is glucose(C6H12O6)
• Energy is obtained form food by respiration
• Respiration: Glucose+oxygen —> carbon dioxide+water

  Exothermic(energy is released)
• Photosynthesis: Carbon dioxide+water -> glucose+oxygen

  Endothermic(energy is put in)

  Chlorophyll is required as a catalyst. The energy input is from the sun.