Laboratory Exercise #1 Measurement

Laboratory Exercis e #1 Measurement An introduction to science must begin with the basics. In this laboratory we introduce the metric system, the system of measurement embraced by most scientists. The United States is one of the few countries yet to adopt the metric system in everyday life. This is unfortunate because, as you will soon learn, conversions are more easily performed using the metric system than its cumbersome counterpart, the American Standard System. Conversions are easier because the metric system is based on units of ten, as shown in Table 2.1 below: Table 2.1 Metric Units of Measurement Units of Symbol Values length s Kilometer km 1 km = 1000 m Meter m 1m Decimeter dm 1 m = 10 dm Centimeter cm 1 m = 100 cm Millimeter mm 1 m = 1000 mm Micrometer um 1 mm = 1000 um Nanometer nm 1 um = 1000 nm Units of mass Symbols Values Kilogram kg 1 kg = 1000 g Gram g 1g Milligram mg 1 g = 1000 mg Microgram ug 1 mg = 1000 ug Units of volume Symbols Values Liter L 1L Deciliter dl 1 L = 10 dl Milliliter ml 1 L = 1000 ml Microliter ul 1 ml = 1000 ul Conversion Techniques: Several techniques may be utilized to perform conversions. We will examine two of these methods. If you are already comfortable with a technique that we don’t cover, keep using it - provided, of course, that you arrive at the correct answers! Let’s now take a look at our first problem: 23 cm = __.23_____m In this problem, we are asked to determine the number of meters in 23 centimeters. To solve the problem, we have to multiply 23 cm by some number, but we mustn’t change the given value of 23. There is only one number that we can multiply 23 by and not change its value, and that number is one. Now, to complicate things slightly, the number “one” that we are going to multiply by 23 cm must be expressed as a fraction. For this fraction to equal one, its numerator and denominator must be equal. Table 1.1 tells us that 100 cm = 1 m. When we express this relationship as a fraction, it is equal to one. We now have to determine which value to put in the numerator of the fraction and which value to put in the denominator. The units that we are seeking (in this case meters) must be placed in the numerator, while the units that we have (in this case centimeters) must be placed in the denominator. If we express our given value of 23 cm as a fraction by placing it over the number 1, we see that the units for cm will cancel out when we multiply. We will then be left with meters, which is the unit we are seeking. Let’s use all of the information we have covered so far and solve the problem: 23 cm x 1 m 1 = .23 m 100 cm 23m Multiplying across and canceling out units, we are left with 100. When dividing by factors of 10, the decimal point moves to the left. The decimal point moves 1 place to the left when dividing by 10; 2 places to the left when dividing by 100; 3 places to the left when dividing by 1000, and so on. Since we are dividing by 100, we move the decimal 2 places to the left. This leaves us with our answer, which is 0.23 m. Thus, there are 0.23 m in 23 cm! (If we had been multiplying by factors of 10, we would have moved the decimal to the right.) It should now be apparent that conversions simply involve moving the decimal point. You have to determine which direction and how many places the decimal should move. This brings us to another method of unit conversion. Let’s take a look at the same problem and solve it a different way: 23 cm = m We must first identify the equation that explains the relationship between cm and m. From Table 1.1, we see that this equation is 100 cm = 1 m. We write this equation above our problem, keeping similar units on the same side: 100 cm = ____ 1m 23 cm = __.23__ m Since there are two zeros in 100 cm, we know that we will move the decimal point two places, but should it be moved to the right or to the left? We can try both, actually, and determine our final answer using common sense. If we move the decimal to the left, our answer is 0.23 m. If we move the decimal to the right, our answer is 2300 m. Since 100 cm = 1 m, and we have decreased our value in cm to 23, we should see a corresponding decrease in meters in our answer. The correct answer is therefore 0.23 m, the same answer that we came up with using the first method. Solve the practice problems below to determine how proficient you are at unit conversions and check your answers with the answer key. Practice Problems: 1) µm 2) 3) mm 4) 37 mm = _______37000___ µm 62 µm = __.0.062____.____ mm 2.1 cm = .021 5) 932.7 nm = _93270_________ 6) 1.72 mm = _____.00172______m m 0.35 nm = ___.00035_______ µm 7) 47.5 µm = ____.0475______ 8) 8.23 mm =_____.823_____cm LENGTH, MASS, VOLUME AND TEMPERATURE We now introduce the metric units for length, mass, volume and temperature. As you work through the lab, record your answers. You will submit all answers in the Results section at the end of the lab. LENGTH is the measure of a line end to end. The unit of measurement for length is the meter (m). Experimental Procedure: 1. Use the metric side of the ruler to measure the diameter of the top of the cup in your lab kit in centimeters. Convert to meters, then to millimeters, as indicated below. ____.92____cm = .092 m= 92 mm To demonstrate how much easier conversions are in the metric system than American Standard, repeat your measurement, this time measuring in inches and then doing the indicated conversions. ______4 3/8___in = .4479 ft = .149 1 inch=.0833 inches 1 foot = 1/3 yards .0833 x 4.⅜ = .4479 .4479 x 1/3 yds 2. Use the ruler to measure the length from your elbow to your wrist in centimeters. Convert as indicated: _____30_____cm = .3 m= 300 mm 3. a.Estimate the length of your index finger. ____3_______ cm b. Use the ruler to measure the length of your index finger. ______3.1_____cm 4. Estimate your height. _____189______ cm View the following video: Measuring height for a demonstration of actual measurement of height and then measure your actual height using the ruler. ____189________ cm MASS is the quantity of matter an object has. The unit of measurement for mass is the gram (g). Frequently, weight and mass are used interchangeably, but there is a difference. Mass, the amount of matter in an object, does not change. Weight, on the other hand, is determined by gravitational pull and can change. For example, your mass will be the same on earth as it is on the moon, but your weight will be different. A scale is used to measure mass. The display on the scale must be set at exactly zero before weighing an object in order to obtain an accurate measurement of mass. Setting the scale to zero is known as taring. View the video to see how a scale is tared. . Then view the next video to observe the measurement of the mass of an Erlenmeyer flask. Experimental Procedure: 1. Determine the mass of a domino on the scale by viewing the video. Use the exact number on the scale. Do not round. Convert as indicated. 4.9 g = 4900 mg I was able to find this online 2. Determine the mass of the pebble on the scale by viewing the video. Use the exact number on the scale. Do not round. Convert as indicated. g= mg 3 a. Estimate the mass of a set of keys. ___________g=___________mg b. Read and record the actual mass of the keys ___________g=___________mg 4 a. Estimate the mass of a graduated cylinder ___________g=___________mg b. Read and record the actual mass of the graduated cylinder in the video. ___________g=___________mg VOLUME is the amount of space an object occupies. The standard unit of measurement is the liter (L). Since volume measures the three dimensions of space, volume can also be expressed using the measurements of length. (length x width x depth) Experimental Procedure: Use the ruler to determine the length, width and depth of the domino in your lab kit. Length = __4.34____cm Width = __2.14____cm Depth = ___.76___cm To calculate the volume of your domino, multiply length x width x depth. The answer obtained is in cubic centimeters (cm3), which must be converted to milliliters. This conversion is simple, since 1 ml = 1 cm 3. L x W x D = ____7.058__ cm3 =___7.058____ ml Convert your answer to liters: __.007058______ L Calculate the volume of your cell phone using the same formula as above. ____94____ cm3 157.5 x 77.4 x 7.7 93866.85mm Convert your answers to liters: ___.094_____ L In the laboratory, graduated cylinders are used to measure volume in milliliters or liters. Fill a 25 ml graduated cylinder with 17 ml of water. * See photograph #1 (below). When using a graduated cylinder, there are a few things you should be aware of. First, due to certain properties of water, you will see that there is a curve on the surface of water. This is called a meniscus, and you should read the lowest part of the meniscus. Second, you should make sure that you are at eye level with the meniscus when recording the volume. Most graduated cylinders have certain lines that go all the way around the cylinder. You are at eye level when you can no longer see the line on the other side. Finally, make sure that you can determine the value of each increment, since cylinders may be marked differently. Read the volume of water in the graduated cylinder in photograph #2 below and record in Table 2.5. ____17___ml and convert to Liters ___.017__L Fill the cup from your lab kit to the top with water. Using the graduated cylinder in the lab kit, fill it as many times as necessary to measure the volume of water in the cup. Record the volume of the cup _______ml, and convert to Liters _____L. Archimedes’ Theory of Displacement states that an object will displace a volume of water equal to its own. View the video and then perform the volume displacement experiment as described below. Volume displacement experiment: Calculate the volume of the small marble in your lab kit. Fill a 25 ml graduated cylinder with 20 ml of water, then drop in the marble. The amount of water displaced by the marble is equal to the volume of the marble. Record the volume of the marble and convert to liters. ml = L There will be times throughout the semester when you will add drops of liquids to solutions. To grasp an understanding of the actual volume you will be adding, determine the number of drops in 1 ml of water. Gather a 10 ml graduated cylinder, a paper cup filled with water and a pipette. Using the pipette, count the number of drops it takes to reach 1 ml in the graduated cylinder. There are approximately drops/ml TEMPERATURE - Thermometers are used to measure the degree of hot or cold (the temperature) of an object. There are two common scales of temperature measurement that are used for doing this, Celsius and Fahrenheit. They are related in the following way: oC = 5/9(oF – 32) oF = 9/5 o C + 32 Experimental Procedure: View the following videos to read and record the temperatures of the three samples of water in Celsius and then convert to Fahrenheit. Ice Water oC = oF ent. Room Temperature Water Warm Water ____________oC =_____________oF oC = oF Estimate the outdoor temperature right now. ______80________ oF Determine the actual outdoor temperature (If you have a thermometer outdoors, use it to determine the temperature. If not, search online for the temperature in your area right now). Record the temperature in oF and then convert to oC. ____82______oF = ____27.78______oC (82-32) x 5/9 50 x 5/9= 27.78 BIOL 101 Laboratory Exercise #1 Measurement Results Copy and paste the following to a WORD document, fill in the answers and submit the assignment as a file upload. Each question is worth 2 points. Incorrect estimations will not be penalized, but the conversions will be graded. Table 2.2: LENGTH ------------------------------------------------------- cm m mm Diameter of cup Diameter of cup (American Standard System) inches feet cm m -------------------------------------------------------- Elbow to wrist Estimated length of index finger Actual length of index finger Estimated height Actual height Table 2.3: MASS g Mass of domino Mass of pebble Estimated mass of set of keys mg yards mm Actual mass of set of keys Estimated mass of graduated cylinder Actual mass of graduated cylinder Table 2.4: VOLUME Length (cm) Width (cm) Depth (cm) Volume (mL or cm3) Volume (L) Domino cellphone Table 2.5 VOLUME Volume (ml) water in graduated cylinder in photograph #2 cup marble # of drops in 1 ml _________ Table 2.6 TEMPERATURE Volume (L) o C Ice water Room temperature water Warm water Estimated outdoor temperature Actual outdoor temperature ----------------- oF