What does it mean when delta H is negative?

When ΔH (delta H) is negative, it indicates that a chemical reaction or a physical process releases heat energy into the surroundings. In other words, the system undergoing the reaction or process is losing energy in the form of heat. This negative change in enthalpy (ΔH) is often associated with exothermic reactions or processes.

Exothermic reactions involve the conversion of reactants into products while releasing heat energy. Examples of exothermic processes include combustion reactions, where a fuel reacts with oxygen to produce heat and light, and neutralization reactions, where an acid and a base react to form water and a salt, releasing heat in the process.

Mathematically, ΔH is expressed as:

ΔH = H(final state) - H(initial state)

where H represents the enthalpy of the system. If the final state has a lower enthalpy than the initial state, then ΔH will be negative, indicating an exothermic process.