Hydrogen and oxygen can combust to produce heat, and the heat generated can be calculated using the standard enthalpy of combustion, which is 287 kJ/mol for the reaction 2H2 + O2 → 2H2O. If the molar ratio of hydrogen to oxygen deviates from 2:1, complete combustion may not occur, affecting the total energy output. To calculate the energy produced, one can multiply the heat of combustion by the number of moles of hydrogen present. Additionally, while oxygen does not have a heat of combustion, if mixed with other combustible elements, their heats can be summed for total energy calculations. Temperature can be derived from heat energy, but requires knowledge of the initial temperature and specific heat capacity of the system.