• Question: How do you convert chemical enenergy on food to heat energy

    Asked by Peter. C 21 to Aislinn, Fiona, Nathan, Padraic, Sinead on 2 Feb 2015.
    • Photo: Nathan Quinlan

      Nathan Quinlan answered on 2 Feb 2015:


      It’s something like very slow burning. The sugars and other compounds in food react with oxygen, which is carried around from the lungs by blood. That’s as much as I know!

    • Photo: Sinead Quirke

      Sinead Quirke answered on 2 Feb 2015:


      Our bodies convert chemical energy in food to heat. When food undergoes a chemical change in our bodies, such as adding hydrochloric acid in our stomachs during digestion, the chemical changes the energy in the food into heat. Energy can neither be created nor destroyed it just changes form. This whole area of study is called thermodynamics and I’m definitely no expert in field.

    • Photo: Aislinn Coghlan

      Aislinn Coghlan answered on 3 Feb 2015:


      Thermodynamics is something chemical enigneers study quite a bit. When a reaction takes place and gives out heat, it is called an exothermic reaction. In contrast, a reaction can also use up heat energy and this is called an endothermic reation.

      Energy is usually stored in the bonds of a chemical compound. When you break these bonds, like hitting a pane of glass with a hammer, you need energy to do it. Therefore an endothermic reaction uses up heat energy to make these bonds.

      Food we eat is not in a form we can use when it is put into our mouths. We first have to break it down during the process of digestion. This involves breaking bonds that takes energy. We now how small molecules that make up the building blocks of our bodies.

      When it is time for our body to use these building blocks to repair cells, we have to put them back together in the right sequence. This involves making new bonds which is an exothermic process- it gives off heat.

      So when you are running around playing sports, you are making your body repair things much faster to keep up with the external stress you are placing on your body. This involves the formation of lots of chemical bonds that give off heat, which your body then has to counteract by getting sweaty to cool you down again.

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