SI units and dimension formula
The IUPAC recommended seven physical quantities has thair own SI units and dimension. Other physical quantities like force, energy, work, heat, etc can be derived from the basic SI unit. But SI unit of luminous intensity or candela not needed in chemistry. It used in optical photochemistry but it included only for the shake of completeness.
In physical chemistry, we commonly deal with quantities such as pressure, volume, mass, temperature, current, etc. These quantities are physical quantities and are two types
- The quantity which has a magnitude but not a definite direction known as a scalar quantity.
- But quantity which has both magnitudes and direction known as a vector quantity.
Every physical quantity has two components, namely, the numerical value and unit.
Physical quantity = numerical value × unit
Thus the quantity 5 Joule means, numerical value = 5, and unit = 5 Joule.