BIOL1406/ metric
Name:_________________________ BIOL 1406____________________ Date:________________ The Metric System Most countries around the world use International System of Measurements (SI), or the “metric system”, as their system of measurement. We here in the United States most often use the English system in our day-to-day lives. For example, you are familiar with such terms as inch, foot, mile, etc. However, in science, it is important that measurements be standardized throughout the world to avoid unnecessary confusion as information is exchanged internationally. Thus, even here in the U.S., scientists use the metric system. The metric system is based on units of 10. The main basic units of measurement we will use in this course are as follows: Length: meters (m) Volume: liters (L) Mass: grams (g) Temperature: degrees Celsius (ºC) or Kelvin (degrees Celsius + 273.15) Making accurate measurements allows scientists to objectively describe what they observe. Accuracy is how close to actual, true value a set of measurement of the same thing are. Precision is how close together the repeated measurements are to each other. Like hitting a target, accurate shots will be close to the bull’s eye and precise shots will be very close together in where they hit. Being based on tens makes conversions within the metric system easy. Different prefixes can be placed before the base units (meter, liter, or gram) when measuring large or small quantities. For example, the distance from Dallas to Fort Worth is measured in kilometers (km). The length of a bacterium is usually measured in micrometers (µm) also called microns (μ) Use the website https://www.nist.gov/pml/weights-and-measures/metric-si-prefixes 1. Indicate the symbol for the following metric prefixes: nano _____ milli _____ centi _____ micro _____ kilo _____ deci _____ mega _____ giga _____ 2. Express the following metric prefixes in scientific notation (example centi = 10 -2): nano _____ micro _____ kilo _____ deci _____ mega _____ giga _____ no prefix _______ 3. Complete the following metric conversion problem: a. 3.5 mg = ___________________ µg b. What is the exponent for nano______ milli _____ micro _______ 4. Define accuracy_______________ Define precision___________________ 4. Which unit is used for length measurements (meter, gram, liter)? _____________________ 5. Which unit is used for volume measurements (meter, gram, liter)? ___________________ 6. Which unit is used for mass measurements (meter, gram, liter)? _____________________ 1 Name:_________________________ BIOL 1406____________________ Date:________________ 7. What do the smallest lines on the metric ruler represent? ___________________________ 8. What unit do the numbers on a metric ruler represent? _____________________________ 9. Which measuring device should you use to measure 95 mL (100 mL graduated cylinder, 500 mL beaker, or scale)? ________________________ 10. Which measuring device should you use to measure 0.25 mL? (10 mL graduated cylinder, 1 in 1/100 mL pipette, 1 in 1/10 mL pipette) ______________________________________ 11. Which two instruments can be used to determine the mass of an object? ________________ ________________________ and _______________________________________________ 12. What does it mean to tare the electronic balance? ___________________________________ ______________________________________________________________________________ Use the metric system link in eCampus: https://www.nist.gov/pml/weights-and-measures/metric-siprefixes to complete the following chart. Go to insert-symbol to find any special characters you need, or copy and paste it from the text on the first page. Prefix Giga Mega Kilo Hecto Deka No prefix Deci Centi Milli Micro Nano Abbreviation Scientific notation Decimal notation G 109 1,000,000,000 – 100 1 Converting within the metric system: There are several ways to convert within the metric system. 1. Move the decimal point method Because the metric system is based on units of 10, it is very easy to make conversions within the system. We start with the base unit, which is meters (m) for length, liters (L) for volume, and grams (g) for mass. Then we just need to know if we are converting to something bigger or smaller compared to the base unit. If we are getting bigger, we will move the decimal point to the right each 2 Name:_________________________ BIOL 1406____________________ Date:________________ time we go up by a factor of 10. If we are getting smaller, we will move the decimal points to the left by a factor of 10. Example: How many centimeters are in a kilometer? Looking at the table above, this entails we need to go from small to big, and we will be moving the decimal point to the right 5 times: 1.0 cm 🡪 100,000.0 km. 2. Subtract exponents method Subtract the exponents associated with the prefixes and then to move the decimal point the indicated number of units. This method only works within the metric system and cannot be used to convert between metric and English units. Example: 7.5 km = _____ mm Kilo = 103 Milli = 10-3 Exponent for the starting prefix minus (–) Exponent for the ending prefix 3 – (-3) = 6 If the answer is positive, move the decimal point that many places to the right. The number will get larger. You may add zeros as needed to move the decimal point. Keep track of those negative signs and remember that when a negative is subtracted, the negative signs cancel, and it becomes addition. Since the answer is 6, you move the decimal point 6 places to the right. 7.5 km = 7500000 mm If the answer is negative, move the decimal point that many places to the left. The number will get smaller. You may add zeros as needed to move the decimal point. 3. Dimensional analysis method Multiply the amount by a conversion factor, which is a fraction that equals 1 and has the unit you are converting to on the top (numerator) and the unit you are converting from on the bottom (denominator). You will multiply straight across, NOT cross-multiply in this method. The advantage of this method is that it can be used in any system, not only within the metric system. For example: 10 inches = ? cm Conversion factor: 2.54 cm/1 inch 10 inches x 2.54 cm/1 inch = 25.4cm, inches divided by inches will cancel out inches, leaving cm. That part about the units canceling because the same unit is divided by itself is what makes this method work. Always check to make sure the unit you are converting from will cancel in this method (meaning, it will be divided by itself). 3 Name:_________________________ BIOL 1406____________________ Date:________________ Using one of the techniques described above for converting within the metric system, solve the following conversion problems (show your work!). a. 10 mm = ? cm b. 51 mL = ? liters c. 1.2 kg = ? mg d. 10.4 m = ? μm e. 2.35 L = ? nL Converting between the metric and English systems: Let’s say you decide to take a trip to Europe. Upon arriving in Europe, you rent a car and start to drive towards your hotel. You notice that the speed limit sign says 100km/hr. You are used to seeing signs in mi/hr. What do you do? When you buy some apples from the grocery store, they are weighed in grams. You are used to buying by the pound. What do you do? Fortunately, there are simple conversion factors that will allow you to convert measurements from the English system to the metric system (and vice versa). Here are some basic conversions you may need in today’s lab activity and throughout the course: Within the English system: 12 inches = 1 foot 3 feet = 1 yard 1 lb = 16 oz Conversions between systems: 1 in = 2.54 cm 1 mi = 1.6 km 1 g = 0.04 oz 1 gallon = 3.79L 1 kg = 2.2 lb More conversions can easily be found online. The average room temperate us 72 ď‚°F in the box below. The freezer temperature is usually 0 ď‚°C Table: To convert from Fahrenheit to Celsius, you use this following equation: ºC = (5/9)*(ºF – 32) To convert from Celsius to Fahrenheit, you need to use the following equation: ºF = [(9/5) * ºC] + 32 Convert the following temperatures, show your work! a. 100 ºC = ? ºF b. 32 ºF = ? ºC c. 98.6 ºF = ? ºC d. 20 ºC = ? ºF Save your completed lab and upload it to ecampus, then take the metric system quiz. 4
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