MATTER AND ENERGY 77 



36. Matter and Energy. All chemical 

 phenomena are associated with changes in 

 energy, one of the great conceptions of modern 

 physical science. Energy may be latent or 

 locked up in a chemical substance, and it is 

 then said to be potential. Thus, take any oil 

 as an example. An oil contains carbon, 

 hydrogen and oxygen so united as to form a 

 complex substance, say the olein of olive oil, 

 each molecule of which has a definite chemical 

 composition. The oil (or the olein), however, 

 is conceived to be associated with energy in 

 a latent state, that is to say, the energy that 

 binds the atoms into its molecule is there 

 locked up, and so long as it is so, the molecule 

 is chemically inert. But if it be oxidized, that is 

 if it be burned in a suitable contrivance, say a 

 lamp, the oxygen of the air unites with the 

 carbon of the oil to form carbonic acid, and 

 with the hydrogen, to form steam or water. 

 The carbon appears in the form of soot. 

 But during the burning, energy appears as 

 heat, and the heat, by a suitable machine, 

 might be converted into motion, and do 

 work by lifting a weight and overcoming the 



