Full lecture 2: measurements and units: scientific method. Observations: natural phenomena and measured events; can be stated as a law if universally consistent. Hypothesis: tentative and testable explanation for an observation or a series of observations. Experiment: procedure to test hypothesis; measures one variable at a time. Scientific theory: general explanation of widely observed phenomena that have been extensively tested. Further experiment: tests predictions based on model. Length(l), mass(m), time(t), temperature (t), amount (n), meter(m), kilogram(kg), second(s), kelvin (k), mole(mol) All scientific measures are subject to error. These errors are reflected in the number of figures reported for the measurement. These errors are also reflected in the observation that two successive measures of the same quantity are ifferent. Accuracy: how close the measurement is to the actual value. Precision: how well can the measurement be repeated. Accuracy can be true of an individual measurement or the average of several. Precision requires several measurements before anything can be said about it.