The demonstration of conservation of mass by Antoine Lavoisier in the late 18th century was a milestone in the development of modern chemistry. When two pure substances react to form a compound, they do so in a definite proportion by mass. For example, when water is formed from the reaction between hydrogen and oxygen, the 'definite proportion' is 1 g of H for every 8 g of O. law of multiple proportions. When one element can combine with another to form more than one compound, the mass ratios of the elements in the compounds are simple whole-number ratios of each other. Note that the second ratio is exactly twice the first, because there are exactly twice as many oxygens in CO 2 per carbon as there are in CO. law.
Natural laws summarize patterns that recur in a large amount of data.
Le Chatelier's principle. Le Chatelier's principle predicts that when a stress is applied to an equilibrium mixture, the equilibrium will shift to relieve the stress. Stresses include temperature changes, pressure changes, and changes in the concentrations of species in the mixture. A naturally occuring aliphatic amino acid with a nonpolar side chain. Compare with dextrorotatory .