Name Section Date Experiment 1 PreLab Questions a Write def

Name Section: Date: Experiment #1 Pre-Lab Questions . (a) Write definitions to distinguish between the terms: accuracy and precision. (b) Write definitions to distinguish between systematic and random errors (c) How would a large systematic error affect the accuracy and precision for a set of measurements? 2 Why should you use a stopper to cover your flask? State the rules concerning significant figures: (a) for addition or subtraction (b) for multiplication or division. Experiment 1 45

Solution

1. a) Accuracy refers to the closeness of a measured value to a standard or known value. For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value.

Precision refers to the closeness of two or more measurements to each other. Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy.

b)Random errors are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device. Random errors usually result from the experimenter\'s inability to take the same measurement in exactly the same way to get exact the same number.

Systematic errors, by contrast, are reproducible inaccuracies that are consistently in the same direction. Systematic errors are often due to a problem which persists throughout the entire experiment.

c)Systematic errors affect the accuracy of a measurement. In the absence of other errors, repeated measurements yield results that are consistently different from the acceped value by the same amount. The accuracy of measurements affected by systematic errors cannot be improved by repeated measurements.

2. We cover the contents of flask so that they don\'t get spilled when we swirl the flask or just in case we drop it.

3.a)

For addition and subtraction, look at the decimal portion (i.e., to the right of the decimal point) of the numbers ONLY. Here is what to do:

1) Count the number of significant figures in the decimal portion of each number in the problem. (The digits to the left of the decimal place are not used to determine the number of decimal places in the final answer.)

2) Add or subtract in the normal fashion.

3) Round the answer to the LEAST number of places in the decimal portion of any number in the problem.

b)The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer.