| These are the conditions under which, by convention, the physical properties of chemical reactions are studied and quoted.
The enthalpy change that takes place during a reaction, or the electrode potential of a chemical cell, depends on the temperature and pressure of the system, and on the concentration of any reactants in solution. Standard conditions are required to ensure that comparison of the characteristics of different systems - say for enthalpy change - are valid.
The standard conditions are:
- Temperature = 298 K
- Pressure = 1 atm
- Concentration = 1M
Physical changes, such as enthalpy change, measured under these conditions are known as "standard", and are given the symbol θ in superscript. A standard enthalpy change, for example, is quoted as ΔθH. | 
