Ch 5 Measurements Scientific measurements are based on the metric system. This is a decimal based system that uses a system of prefixes to relate the magnitude of the quantity. It is essential that you are able to work fluently in the metric system.

It was the Greeks who developed the "foot" as their fundamental unit of length. Legend has it that this Greek unit was based on an actual measurement of Hercules' foot.

People measured a yard of cloth by the distance between the end of the outstretched arm and their chin. <>

A cubit is the first recorded unit of length and was one of many different standards of measurement used through history.

The Romans measured their pace steps, of about 2.5 feet, 1000 double paces formed a mile.

English Units of Length Ell Unit of length. Very, very old. The English ell should be taken as 45 inches, or a yard and a quarter, and the Scots ell is 37 Scots inches, or 72.2 English inches. Very much not used. Fathom Unit of length, or rather depth, equal to 6 feet. Still encountered. Foot Unit of length. 12 inches, 3 feet to the yard. Very, very common. Furlong Unit of length, equal to 220 yards, or 10 chains. There are 8 furlongs to the mile. The name seems to derive from the length of a furrow, somehow. This unit is still used, especially so in horse-racing.

Enough Already! The metric system is an internationally agreed set of units for measurement. Since 1960, the metric system is correctly known as the SI system, which is short for System International d'Unites (International System of Units). However, it is still commonly (although somewhat incorrectly) continues to be referred to as the metric system. It has only seven basic measures known as units.

Metric Quantities The standard unit of length is the meter (m). The standard measure of mass is the gram (g). The standard unit of time is the second (s). Chemistry uses the cgs system The standard unit of Temperature is Celsius (C) or Kelvin (K) T k = T c The standard unit of volume is either: Cubic centimeters (cc) 1 m = 1,000,000 cm 3 Liters (L) 1 L = 1000 mL Milliliters (mL) 1 mL = 1 cc

Metric Prefixes

Converting Units Q Q How many decimal places do I move it?? A A Please do not ask this question or use this technique. We will use a system of conversion called dimensional analysis. It converts a value using factors of one that have both the known and unknown quantities in them. We will use the same technique for metric to English and metric to metric.

Technique Determine the given and unknown unit. Find a conversion between the given and unknown unit. Turn the equality into a ratio by placing the known unit in the denominator. Multiply the conversion ratio by the known value; cancelling out the undesired units. Round your answer correctly.