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Measuring Mass What is Mass? • Mass is the measure of the amount of matter in an object. • Mass and Weight are different. Weight is the amount of gravitational force pulling on an object. • Weight can also change from place to place (planet to planet), but mass always stays the same. Metric Units of Mass Measurement • • • • • • • Gram (g) – Unit of measurement (starting point) Milligram (mg) – (1 thousandth of a gram, 0.001, 10-3) Centigrams (cg) – (1 hundredth of a gram, 0.01, 10-2) Decigram (dg) – (1 tenth of a gram, 0.1, 10-1) Decagram (dag) – (ten grams, 10, 101) Hectogram (hg) – (1 hundred grams, 100, 102) Kilogram(kg) – (1 thousand grams, 1000, 103) • The units decigram, decagram and hectogram are not used as much as the other units. • Grams are used to measure the mass of larger things such as candy bars. • Kilograms are used to measure the mass of even larger objects like cars. Metric Conversions • To convert larger units to smaller ones , you MULTIPLY by units of 10 • To convert smaller units to larger ones you DIVIDE by units of 10 – Example: 1000 100 10 1 0.1 0.01 0.001 Kilogram hectogram decagram Unit (gram) decigram centigram milligram – To convert 2 grams to centigrams (1 hundredth of a gram), you multiply by 100: • 2 x 100 = 200 cg (2 grams = 200 centigrams) – To convert 3 milligrams (1 thousandth of a gram) to grams, you divide by 1000 • 3 ÷ 1000 = 0.003 g (3 milligrams = 0.003 g) OR • Find out how far apart the two prefixes are on the line above. For example, kilo and hecto are one place apart, kilo and deca are two places apart, etc. • Move the decimal point to the left to convert smaller units or right to convert larger units by the number of places you found in the previous step. If there is no decimal in the number, assume it's after the last digit in the number. 1000 kilogram 100 10 1 0.1 hectogram decagram Units (grams) decigram 0.01 centigram 0.001 milligram Example #1 • To convert 1 kilogram to grams (convert larger to smaller), move the decimal 1 place to the RIGHT and add zeros where needed for the number of places you move down the table. Decimal Point Start 1 kilogram 0 hectogram End 0 0 decagram gram • 1 kilogram = 1000 grams decigram centigram milligram Example #2 • To convert 1 milligrams to grams (convert smaller to larger), move the decimal 1 place to the LEFT and add zeros where needed for the number of places you move down the table. Decimal Point End kilogram hectogram decagram gram • 1 milligram = 0.001 grams 0 decigram 0 centigram Start 1 milligram Convert the following measurements • 8 grams to centigrams • 6.568 kilograms to grams • 2 grams to milligrams 800 cg _________ 6568 g _________ 2000 mg _________ • 9.85 centigrams to grams 0.0985 g _________ • 4 decigrams to grams 0.4 g _________ • 5 milligrams to decigrams 0.05 dg _________ How to Measure Mass You can use a triple-beam balance or hanging balance to find the mass of various objects. The objects are placed on the pan and then you move the weights on the beams until you get the lines on the right-side of the scale to match up. Once you have balanced the scale, you add up the amounts on each beam to find the total mass. What would be the mass of the object measured in the picture? _______ + ______ = ________ 300 70 + _______ 373.4 g 3.4 How to Use a Triple-Beam Balance 1st – Place the object on the pan. 2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place. 3rd – Repeat this process with the top weight. When the arm moves below the line, back it up one groove. 4th – Slide the small weight on the front beam until the lines match up. 5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram. How to Use a Hanging Balance 1st – Place the object on the scale. 2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place. 3rd – Repeat this process with the top weight. When the arm moves below the line, back it up one groove. 4th – Slide the small weight on the front beam until the lines match up. 5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram. Measuring the Mass of a Liquid Mass of beaker with liquid 10 grams - Mass of beaker without liquid 3 grams = = Mass of the Liquid 7 grams Find the mass of the following objects on your desk 5.97 g • Washer __________ 5.20 g • Small Density Cube __________ • Two Large Paper Clips__________ 3g 29.10 g • 50 ml beaker (empty) __________ • 20 ml of water __________ 18.79 g