Base unit (measurement) aspects of the world, such as time, distance, velocity, mass, temperature, energy, and weight, and "units" are used to describe their magnitude or quantity. Many of these quantities are related to each other by various physical laws, and as a result the units of a quantities can be generally be expressed as a product of powers of other units; for example, momentum is mass multiplied by velocity, while velocity is measured in distance divided by time. These relationships are discussed in dimensional analysis. Those that can be expressed in this fashion in terms of the base units are called .
Molar mass water: "M"(HO) ≈ . The molar mass of atoms of an element is given by the Standard atomic weight of the element multiplied by the molar mass constant, "M" = 1 × 10 kg/mol = 1 g/mol: Multiplying by the molar mass constant ensures that the calculation is dimensionally correct: standard relative atomic masses are dimensionless quantities (i.e., pure numbers) whereas molar masses have units (in this case, grams/mole). Some elements are usually encountered as molecules, e.g. hydrogen (H), sulfur (S), chlorine (Cl). The molar mass of molecules of these elements is the molar mass of the atoms multiplied by