Upon encountering a new topic, try this: imagine that you are the first person ever to see the laboratory results on which it is based. Imagine that you must construct the new concepts and explanations to interpret these results, and that you will present and defend your conclusions before the scientific community. Be suspicious. Cross-check everything. Demand independent confirmations. Always remain, with Boyle, the “skeptical chemist.”
Chemical reasoning, as used both in applications and in basic research, resembles a detective story in which tangible clues lead to a mental picture of events never directly witnessed by the detective.
The science of chemistry rests on two well-established principles: the conservation of matter and the conservation of energy.
Chemists think in the highly visual nanoscopic world of atoms and molecules, but they work in the tangible world of macroscopic laboratory apparatus. These two approaches to the chemical sciences cannot be divorced.
Investigating chemical reactions can be greatly complicated and often obscured by the presence of extraneous materials. So, the first step, therefore, is to learn how to analyze and classify materials to ensure that you are working with pure substances before initiating any reactions.
The definite mass ratios involved in reactions suggested a convenient method for counting the number of atoms of each element participating in the reaction. These results, summarized as the laws of chemical combination,provided overwhelming, if indirect, evidence for the existence of atoms and molecules.
Knowledge of the components of the atom and of the forces that hold them together stimulated entirely new fields of basic science and technology that continue to the present.
Laboratory or industrial chemical reactions are carried out with quantities that range from milligrams to tons, so we must be able to relate the relative atomic mass scale to the macroscopic scales used in practice. The link between the two scales is provided by Avogadro’s number (N).
The conservation of matter in a chemical change is represented in a balanced chemical equation for that process. The study of the relationships between the numbers of reactant and product mole\xadcules is called stoichiometry. Stoichiometry is fundamental to all as\xadpects of chemistry.
We point out that not every reactant is completely consumed in a chemical reaction, and that the limiting reactant determines the maximum theoretical yield; the percentage yield may be somewhat less.
The shapes of molecules influence their behavior and function, especially the ease with which they can fit into various guest-host configurations important in biology and biochemistry.
Quantum mechanics explains the physical stability of the atom by predicting its allowed discrete energy levels and defining the wave functions (also called atomic orbitals) associated with each energy level. The orbitals determine the probability density for finding the electrons at particular locations in the atom when the electrons are in a specific quantum state.