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research food food preservatives additives food additives organic chemistry problem skills in research process skills advantages and disadvantages of observation purpose of observation observation chemistry chemical equation balance telescope projects ched programs planning concept statistics physics distance displacement motion formal and nonformal education internal analgesic analgesic type of over-the-counter drug drugs otc type of otc prescription drugs over-the-counter drugs history history of organic chemistry chemisry chemical chemical changes naming compounds naming organic compounds nomenclature earth's movement plate tectonic effects of food additives types of food additives preservatives research problem