Anti-de Sitter space bell. It might be described as being the "opposite" of the surface of a sphere, which has a positive curvature. General relativity is a theory of the nature of time, space and gravity in which gravity is a curvature of space and time that results from the presence of matter or energy. Energy and mass are equivalent (as expressed in the equation "E" = "mc"), and space and time can be translated into equivalent units based on the speed of light ("c" in the "E" = "mc" equation). A common analogy involves the way that a dip in a flat
Thermochemical equation between initial and final states. In other words, it does not matter what steps we take to get from initial reactants to final products—the ΔH will always be the same. ΔHrxn, or the change in enthalpy of a reaction, has the same value of ΔH as in a thermochemical equation, but is in units of kJ/mol being that it is the enthalpy change per moles of any particular substance in the equation. Values of ΔH are determined experimentally under standard conditions of 1atm and 25 °C (298.15K). As discussed earlier, ΔH can have a positive or negative sign. A positive