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).
A mole is a measure of chemical substances. There are 602,300 million trillion (6.023 x 10 23) atoms or molecules in one mole. A mole of any two elements will have a different mass, but the same number of particles. pure substance consists of a single element or compound. Iron is formed only of iron (Fe) atoms; table salt is formed only of sodium chloride (NaCl) molecules. A mixture, however, is made up of different compounds and/or elements.