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Universidad de Puerto Rico en Cayey Departamento de Biología Laboratorio de Biología General I BIOL:3033
Agosto 2012

Laboratory #1: : Metric Units and Conversions in Biology Objective: Students should be able to: 1. recognize laboratory equipment as well as their function. 2. explain the concepts of measurements such as length, volume, weight, and mass 3. explain the difference between thestandard system of measurement and the Metric system 4. describe how to care for a microscope 5. define and use basic descriptive statistical parameters and % error

Background: The metric system is the world standard for measurement. Not only is it used by scientists throughout the world, but most nations have adopted it as their standard of measurement. All of the measurements done in thiscourse will use the metric system. The system is based upon measures of distance (in meters), volume (in liters), and mass (in grams). Scales of measurements increase or decrease as multiples of ten which facilitates expression of measurement values using the decimal system (Table 1 & 2). Table 1. The metric system uses a two-part representation of all measurements. The first character or prefixindicates the power of 10 used, while the remainder of the measurement is the base unit.

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How to convert within the metric system using the B—S rule - First, learn where the metric prefixes are along the metric scale. Each notch on the metric scale represents one power of 10. This means you would either multiply or divide by 10 when moving one notch on the metric scale (Table 1).

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- Determine the number of notches between the unit you have and the unit you want. This is the number of places that you will move the decimal point when converting between the two units. Moving the decimal one place to the right is the same as multiplying by 10. Moving the decimal point one place to the left is the same as dividing by 10. A. Metric system conversionsusing dimensional analysis Dimensional analysis is a method of converting between different units of measurement. While it requires a bit more set-up on paper, it has the advantage of built-in checks and balances. In other words, you can tell if you set up a problem correctly by whether the units cancel. To start, consider that all measurements consist of a numerical value and a unit (Table 2).You should always include the units when writing any number in your lab notebook; without the units, the number is often meaningless. Table 2. Below you will find convertion relations for English and a metric units based upon measures of distance (in meters), volume (in liters), and mass (in grams). Linear Measure: Area Measure: Volume Measure: 1 ft = 12 in 1 acre = 160 sq rods 16 oz = 1 pt 1 yd =3 ft 1 sq mile = 640 acres 2 pt = 1 qt 2 2 1 mile = 5280 ft 1 cm = 0.15500031 in 4 qt = 1 gal 1 rod = 16.5 ft 1 m2 = 1.195990046 yd2 1 gal = 0.13368056 ft3 2 1 furlong = 220 yd 1 km = 0.3861021585 sq mile 1 gal = 231 in3 1 in = 2.54 cm 1 gal = 3.78541178 L 1 ft = 0.3048 m 1 ft3 = 7.48051948 gal 1 yd = 0.9144 m 1 ft3 = 28.31684659 L 1 mile = 1.609344 km 1 L = 0.26417205 gal 1 L = 1.056688209 qt 1 L= 61.02374409 in3 1 L = 0.001 m3 1 mL = 1 cm3
Weight Measure: Temperature Conversions: Time Measure: 16 oz = 1 lb 1 min = 60 s 1 oz = 28.348 g 1 hr = 60 min 1 ton = 2000 lb 1 hr = 3600 s 1 lb = 453.568 g 1 day = 24 hours 1 kg = 2.20474 lb To convert from one unit to another, you simply take the measurement you have, and multiply it by the conversion factor that will convert the units you have tothe units you want. You do this in your day to day life without thinking about it. For example, if you are going to watch a movie that is 90 minutes in length, you 2

mentally calculate that this movie is 1.5 hours long. To do this, you used a conversion factor along the way:

So, to convert 530 milligrams (mg) to grams (g), you would set up the following:

The following exercises are...