Introduction to Basic Laboratory Techniques Measurement Means by

Introduction to Basic Laboratory Techniques • Measurement – Means by which numerical information or data is obtained. – The information should be conveyed through calculations, analysis and conclusion. • Precision – Describes the amount of information in a measurement. – More information with better precision.

Precision… • The measuring instrument must always be examined and the smallest values of the scale must be determined. • The measurement should include all the numbers from the instrument and an additional digit, which is an estimate to the nearest tenth of the smallest division.

Significant Figures and Rounding • Figures that contain meaningful information in view of the error or uncertainty involved. • More the number of significant figures, better the precision is.

Significant Figure Rules • Non-zero digits are always significant. • Any zeros between two significant digits are significant. • A final zero or trailing zeros in the decimal portion ONLY are significant.

Rounding… • If it is less than 5, drop it and all the figures right of it. • If it is more than 5, increase by 1 the number to be rounded, that is, the preceeding figure. • If it is 5, round the number so that it will be even.

Addition or Subtraction • Count the number of significant figures in the decimal portion of each number in the problem. • Add or subtract in the normal fashion. • Round the answer to the LEAST number of places in the decimal portion of any number in the problem.

Multiplication or Division • The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. • This means you MUST know how to recognize significant figures in order to use this rule.

Metric System • The first standardized system of measurement, based on the decimal was proposed in France about 1670. However, it was not until 1791 that such a system was developed. • It was called the "metric" system, based on the French word for measure. • The modern metric system has been renamed Systeme International d'Unites (International System of Units) and is denoted by the letters SI.

Metric System… • There are three major parts to the metric system: the seven base units, the prefixes and units built up from the base units. • Three major parts: – Physical Quantity ; Name of SI unit; Symbol for SI unit.

Metric System… • Here is a list of the base units which make up the metric system: length meter m mass kilogram kg time second s current Ampere A temperature Kelvin K Amount of substance mol luminous intensity candela cd

Metric System…Prefixes Prefix Symbol Numerical Exponential giga G 1, 000, 000 109 mega M 1, 000 106 kilo k 1, 000 103 hecto h 100 102 deca da 10 101 No prefix means 1, i. e. 100

Metric Systems… Prefixes Prefix Symbol deci d centi c milli m micro nano n Numerical Exponential 0. 1 10 -1 0. 01 10 -2 0. 001 10 -3 0. 000001 10 -6 0. 00001 10 -9

Conversion you need to know… • memorize the metric prefixes names and symbols. • determine which of two prefixes represents a larger amount. • determine the exponential "distance" between two prefixes. • significant figure rules.

Powers of Ten and Scientific Notation • In astronomy, one encounters numbers that are often too large or too small. • Power of ten notation is convenient format by which one may easily express values may times larger or smaller. • Scientific notation also helps us to easily write values many times larger or smaller.

Power of Ten Notation • The notation is symbolically shown as 10 n. – 10 is the base and n is an integer and is the power of exponent to which is base is raised. • If the exponent is positive: – 103 = 10 x 10 • If the exponent is negative: – 10 -3 = 1/(10 x 10)=0. 001 – Whenever the exponent is negative, the number or zeros to left of the 1 is one less than the absolute value of the exponent.

Scientific Notation • It is symbolically shown as a. bc x 10 n. – Where a. bc decimal between 1 and 10 and n is an integer, denoting the power of 10. • Average distance between earth to the sun is 93, 000 miles. To convert: – Move the decimal point to the left until the number you get is between 1 and 10. – 9. 3 x 107 miles.

Scientific Notation… • For numbers less than 1: • # 0. 0000013 cm. • To convert this into Scientific Notation: – Move the decimal point to the right until you obtain a value between 1 and 10. – The absolute value of the exponent n is again equals the number of places the decimal point is moved. • The converted number is 1. 3 x 10 -6 cm.

Arithmetic Operation with Scientific Notation • Addition or subtraction: – Adjust the decimal point so that the numbers have same exponent. Then the numbers are added or subtracted and the exponent remains the same. • Multiplication: – Values are multiplied and the exponents are added. • Division: – Values are divided and the exponents are subtracted.

Errors • Human Errors: – Math mistakes, not following direction… • Systematic Errors: – Due to equipment defects that produce consistent mistakes in the same direction. • Random Error: – Due to demanding more precision from the equipment than it was designed to produce.