Bio 105 Lab 1: Metric System, Dimensional Analysis, and Measuring

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1 1 BIO 105 Summer 2013 Name Bio 105 Lab 1: Metric System, Dimensional Analysis, and Measuring The word measure means to determine the size, capacity, extent, volume, or quantity of anything, especially as determined by comparison with some standard or unit. To measure something you need a standard system of units and a device to measure it. A. Metric System 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 Systeme International d'unites (International System of Units). However, it is still commonly referred to as the metric system. It has only seven basic measures (known as units), listed in the following table, of which the first four are in common use and the other three are mainly for technical and scientific purposes. Table 1. International System of Units Type of Measure Standard Unit Symbol Length Meter M Mass (weight) Kilogram* Kg Time Second S Temperature Kelvin** K Electric current Ampere A Amount of substance Mole mol Luminous intensity Candela cd * Although the kilogram is commonly used as a measure of weight, it is actually defined as a measure of mass. Weight is a measure of how heavy something is, whereas mass is a measure of the amount of matter. For everyday use, the difference between mass and weight is irrelevant. ** Temperature is officially measured in degrees Kelvin, but in day-to-day use the Celsius system is used instead. Table 2. Common prefixes used in the metric system Prefix Symbol Factor Nano n 10-9 or Micro µ 10-6 or Milli m 10-3 or.001 Centi c 10-2 or.01 Deci d 10-1 or or 1 Deka da 10 1 or 10 Hecto h 10 2 or 100 Kilo k 10 3 or 1,000 Mega M 10 6 or 1,000,000

2 In the metric system, the standard units of measurement (see above table) are multiplied or divided by an order of 10 to produce larger or smaller units. 2 Table 3. 1 meter, 1 gram, and 1 liter is equivalent to... 1 meter = 1,000,000,000 nm 1 gram = 1,000,000,000 ng 1 Liter = 1,000,000,000 nl 1,000,000 µm 1,000,000 µg 1,000,000 µl 1,000 mm 1,000 mg 1,000 ml 100 cm 100 cg 100 cl 10 dm 10 dg 10 dl km kg kl B. Dimensional Analysis Dimensional Analysis (also called Factor-Label Method or the Unit Factor Method) is a problem-solving method that uses the fact that any number or expression can be multiplied by the number one without changing its value. Example 1: Convert 5000 mm into meters: 5000 mm x 1 m = 1,000 mm Since 1 m = 1,000 mm, you are essentially multiplying 5000 mm by one. The mm cancel and we are left with the units that we wanted. Example 2: Convert 5000 mm to cm: 5000 mm x 100 cm = 1000 mm Since both 100 cm and 1000 mm equal 1 meter, they also equal each other. Again, we are multiplying 5000 mm by one. Do the mm cancel out? Are we left with the units that we wanted? C. Relationship between English and Metric Units Most of the measurements in the United States use the English system of pounds, inches, and ounces. Length Volume Mass English Metric English Metric English Metric 1 in 2.54 cm 1 ft L 1 lb g in 1 m qt 1 L 1 oz g 1 mile km 1 gal L 1 dram g

3 3 To convert from the English system to the metric or visa versa use the same method as you used above. Example: Suppose that a soup recipe directs you to add 3 quarts of water to a pot. How many liters of water are you adding? 3 qt x 1 L = qt Do the units of quarts cancel? Are we left with the units that we were asked for? D. Temperature Scientists use either the Celsius or the Kelvin scale. The Fahrenheit scale is used commonly in non-science settings in the United States. Both Celsius and Fahrenheit scales use degrees as units, the Kelvin scale units are called kelvins. Water freezes at 0 ºC or 32 ºF or 273 kelvins. Water boils at 100 ºC, 212 ºF, or 373 kelvins. K = ºC +273 ºF = (9/5 x ºC) + 32 C = 5/9 (ºF 32) E. Measuring The basic unit of measurement for distance is the meter. Below are examples of distances using the metric system. Procedure 1: Measuring length using the metric system

4 4 Step 1: Using the metric rulers, measure following items. Step 2: Record the length in the table on the next page. Length of binder paper (cm) Length of binder paper (mm) Height of binder paper (cm) Height of binder paper (mm) Width of your outstretched hand (cm) Width of the door to the room (m) Length of your pencil (cm) Length of your pencil (mm) Width of lab bench (m) Width of lab bench (cm) Height of lab bench (m) Height of lab bench (mm) Length of your shoe (cm) Length of your shoe (m) Weights The basic unit of measurement for weight is the gram. Below are examples of weights using the metric system.

5 5 Procedure 2: Measuring weights using the metric system Step 1: Using the triple beam balance, measure the following items and record their weights in the table below, remembering to include units. Step 2: Weigh the empty weigh boat, record the weight below. Step 3: Using the pipet, add 1 ml of water to the weigh boat. Note: The instructor will show you how to use the pipets. Step 4: Weigh the weigh boat with the 1 ml of water, record the weight below. Object Weight (g) Weight (kg) Paper clip Pencil Glass beaker Metal object Empty weigh boat Weigh boat + 1 ml water 1 ml water Procedure 3: Measuring volumes Step 1: First estimate the number of drops of water are in 1 ml of water. Record your guess in the table below Step 2: Fill the graduated cylinder to the 1 ml line using a transfer pipet, counting the drops. Step 3: Record the number of drops in the table below. Step 4: Keep adding drops of water to the 2 ml line, record number below Step 5: Keep adding drops of water to the 3 ml line, record number below Step 6: Take the average of the three measurements Estimated # drops Counted # drops Counted # drops Counted # drops Average Procedure 4: Measuring temperature Step 1: Using the Celsius thermometer, measure the temperature of the room and the water baths Step 2: Record the temperature below in Celsius, Then calculate the temp in Fahrenheit and Kelvin. Water bath A Water bath B Water bath C Celsius Fahrenheit Kelvin

6 6 Homework problems. In order to get full credit, you must show your work. 1. Convert 400 ml to L. 2. Convert 37 ºF to kelvins. 3. Convert 525 mm to dm. 4. Convert 42 µm to mm. 5. Convert 5000 cm into yards. 6. Convert 15 ounces into grams. 7. Convert 37 ºC into ºF. 8. Suppose that you are told by a patient that he weights 80 kg. What does this individual weigh in pounds?