CHEM-0001 Chapter Notes - Chapter 1.4-1.6: Significant Figures, Standard Deviation, Decimal Mark
20 Jan 2017
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Si base units mass length time temp kg m sec. Celsius: based on water properties (0 degrees- freezing point) Kelvin: proportional to kinetic energy of molecules (0k - no movement) Intensive property because m, v increase in proportion to each other. Exact numbers: defined values, counted values, infinite significant figures. Example: 12 eggs in a dozen, 1000g in kg, 2. 54 cm in inch. Numbers obtained by measurement- human errors, equipment errors. Precision: measure of how closely individual measurements agree with one another, measured by standard deviation. Accuracy: measure how closely individual measurements agree with true value. Significant figures: all digits of measured quantity, including uncertain one. Zeros at beginning of number are never significant. Zeros at end of number are significant if number has decimal point. Least certain measurement limits certainty so it determines # significant figures. Result has same # decimal places as measurement with fewest decimal places.
