PHAN 111 LAB PRELIM EXAM

• Significant figures

  Each of the digits of a number that are used to express it to the required degree of accuracy
• Significant figures

  • Used to determine how precise a measurement is
• Rules for significant figures

  1. All non-zero numbers are significant

  2. Zeros between two non-zero digits are significant

  3. Leading zeros are not significant

  4. Trailing zeros to the right of the decimal are significant

  5. Trailing zeros in a whole number with the decimal shown are significant

  6. For a number in scientific notation, all digits comprising N are significant, "10" and "x" are not significant
• Rules for adding/subtracting

  Retain as many decimal places in the final result as the number with fewest decimal
• Rules for multiplying/dividing

  Retain only as many significant figures as those in the number with the fewest significant number
• Rounding off should not be done until the final calculations for the reportable value have been completed
• The reportable value is often the summary value for several individual determinations, the end result, the value compared with the specification (acceptance criterion)
• Scientific notation


  Used to express very large or very small numbers, consists of a number between 1 & 10 followed by x 10 to an exponent
• Converting standard notation to scientific notation

  1. Move decimal point to the right of the first non-zero digit

  2. Multiply the resulting number by the base 10 raised to an exponent

  3. The exponent is the number places moved

  4. If movement is left to right, exponent is negative, if right to left, exponent is positive
• Converting scientific notation to standard notation

  1. Move the decimal point to the right if the exponent is positive

  2. Move the decimal point to the left if the exponent is negative

  3. The number of times to move the decimal point is based on the number of the exponent

  4. Add zeroes for each place moved and remove the power of 10
• Rounding off

  If the rounding digit is followed by a number greater or equal to 5, add 1 to the rounding digit<|>If the rounding digit is followed by a number less than 5, retain the rounding digit and drop all succeeding digits
• Precision


  The reproducibility of results and measurements
• Accuracy


  How close the value is to the actual or true value
• It may be that the results are both accurate and precise, neither or accurate but not precise or not accurate but precise
• Treatment of Data

  1. Read the given data

  2. Compute for the results applying basic statistical tools

  3. Supply the correct rounded off values
• Mean


  The numerical average for a data set, calculated by dividing the sum of the individual values by the size of the data set
• Median


  The middle value when we order our data from the smallest to the largest value. When the data has an odd number of values, the median is the middle value. For an even number of values, the median is the average of the n/2 and the (n/2) + 1 values, where n is the size of the data set.
• Range


  The difference between a data set's largest and smallest values
• Mode


  The value that occurs most frequently in a population
• Standard deviation


  Describes the spread of individual values about their mean
• Variance


  The square of the standard deviation
• Relative standard deviation

  The measure of deviation of a set of numbers disseminated around the mean, calculated as the ratio of standard deviation to the mean for a set of numbers
• Types of errors


  • Determinate or constant errors
  • Indeterminate errors
• Determinate or constant errors are those that, although sometimes unsuspected, may be avoided or determined and corrected once they are uncovered.
• Indeterminate errors are caused by uncontrollable fluctuations in variables that affect experimental results.
• According to specifications, capsule dimensions should not have a percentage error more than 2.5%
• Absolute error

  Vtrue - Vobserved
• Relative error

  Absolute error / Vtrue
• Percentage error

  Relative error x 100
• Measurement


  Essential in setting the properties of an object, useful for determining identity and purity by comparing values to a standard
• The word "measurement" comes from the Greek word "metron," which means "limited proportion"
• The metric system was developed in 1790, revised, and renamed as SI system (System International d'Unites or International System of Units)
• The metric system is used in almost all countries except for the United States
• System of measurement used in the US

  "King Henry Doesn't Usually Drink Chocolate Milk"
• Vernier Caliper

  • Upper jaws - smaller in size and attached to the upper portion

  Lower jaws - designed to grip objects firmly between them for measurement

  Main scale - the large scale which runs along the body

  Vernier scale - a smaller scale attached to the main scale and can move along the main scale as the jaws are opened or closed

  Depth rod - used to measure the depths of holes

  Lock screw - used to fix the position of the jaws

  Thumb screw - provides a grip for the user to slide the jaws easily and adjust the position
• Top Loading Balance

  • Capacity of up to 200 g (or up to 3.4 kg) with the readability of up to 3 decimal places
• Analytical Balance

  • Highly precise laboratory balance for measuring mass, used for exact weighing applications of small amounts of material, has a readability of four decimal places (0.0001 g) and a capacity of up to 320 g
• General Instructions For Care And Use Of Precision Analytical Weights

  Never touch analytical weights with bare hands

  Keep the balance calibrated

  Wear gloves and use the forceps provided when manipulating the weights

  The forceps should have no sharp edge, and when possible, not have metal-to-metal contact with the weights
• Weighing Samples

  Ensure that you weigh the samples only after closing the weighing chamber doors

  Keep the weighing chamber clean to prevent cross-contamination of samples and erroneous readings
• Burette


  • A long, narrow tube with a stopcock at its base
  • Used for accurately dispensing flexible volumes of liquids or solutions