Her behavior has been reinforced (i.e. strengthened). Reinforcement can be external or internal and can be positive or negative. If a child wants approval from parents or peers, this approval is an external reinforcement, but feeling happy about being approved of is an internal reinforcement.
It remained to define the unit of amount of substance by fixing the corresponding mass of carbon 12; by international agreement, this mass has been fixed at 0.012 kg, and the unit of the quantity amount of substance was given the name mole (symbol mol).
The mass of one mole of a substance is sometimes referred to as the molar mass. The atomic/formula mass in grams = one mole of the defined substance. If your are dealing with individual atoms, one mole of equals the relative atomic mass in grams.This can be expressed as a simple formula ...ts a very important way of doing chemical calculations! The theoretical basis is explained in section (b). The mole is most simply expressed as the relative 'formula mass in g' or the 'molecular mass in g' of the defined chemical 'species', and that is how it is used in most chemical calculations.