Introduction to Basic Laboratory Techniques

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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 mole mol luminous intensity candela cd

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

12. Metric Systems… Prefixes Prefix Symbol Numerical Exponential deci d 0.1 10-1 centi c 0.01 10-2 milli m 0.001 10-3 micro  0.000001 10-6 nano n 0.000000001 10-9

13. Conversionyou 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.

14. 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.

15. Power of Ten Notation • The notation is symbolically shown as 10n. • 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 = 10x10x10 • If the exponent is negative: • 10-3 = 1/(10x10x10)=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.

16. Scientific Notation • It is symbolically shown as a.bc x 10n. • 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 93,000,000 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.

17. 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.

18. 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.

19. 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.