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Chapter 2 - PowerPoint PPT Presentation

Chapter 2. Measurements and Calculations. Scientific Notation. All numbers written as C x 10 e where C is a number between 1 and 10 e is a whole number exponent that identifies the position of the decimal. Measurement.

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Chapter 2

Measurements and Calculations

• All numbers written as

C x 10e

• where

• C is a number between 1 and 10

• e is a whole number exponent that identifies the position of the decimal

• Always read a measuring device to the maximum number of digits possible.

• Uncertainty – last digit of a measurement is estimated.

• Always include the units with a measurement.

• The number of digits that are known accurately plus the doubtful digit for a measurement.

• All non-zero digits are significant.

• All zeros between nonzero digits (or significant zeros) are significant.

• Zeros used as placeholders are not significant.

• all zeros to left of 1st non-zero digit are not significant. (For example 0.0068 -- two sig figs the zeros are placeholders.)

• for numbers greater than 1, zeros to the right of last digit are ambiguous if no zeros after decimal point. Assume not significant for this class.

• Zeros after last digit are significant for numbers <1 or if they occur after decimal point for number >1.

• Exact numbers have an unlimited number of significant figures.

• 1 dozen = 12 = 12.00 = 12.00000000

• In multiplication and division, an answer has no more sig figs than the measurement with the least number of sig figs.

• In addition and subtraction, the last digit retained in the sum or difference is determined by the position of the first doubtful digit.

• When working with exact numbers, measured values determine the number of significant figures.

• When rounding off nonsignificant digits round up for 5 and higher, otherwise round down.

Conversion Factors

• Answer 226 in

You have just won 2410 nickels in Las Vegas. How many quarters can you get to play with?

• Answer 482 quarters

SI Units (Metric system) quarters can you get to play with?

• Mass kilogram

• Length meter

• Temperature Kelvin

• Time second

Metric prefixes quarters can you get to play with?

Squared and cubic units meters?

• A field of corn has an area of 343.2 km2. What is the area of the field in m2?

• A bucket has a volume of 3.54 m3. What is the volume in cm3?

Density week. If oil costs \$4.65/kg, how much will 1 years worth of oil cost the plastics manufacturer?

• Ebony is a dark hard wood. A rectangular piece of ebony has a mass of 522 g and a volume of 435 cm3. Find the density of ebony.

Percent g/mL for water, determine the number of pounds of water in the fish tank.

• Jodi, a sculptor, has prepared a mold for casting a bronze figure. The figure has a volume of 225 mL. If bronze has a density of 7.8 g/mL and Jodi likes to use 90.0% of the bronze melted (she sometimes spills), how many ounces of bronze does Jodi need to melt in the preparation of the bronze figure.

Temperature and Heat figure. The figure has a volume of 225 mL. If bronze has a density of 7.8 g/mL and Jodi likes to use 90.0% of the bronze melted (she sometimes spills), how many ounces of bronze does Jodi need to melt in the preparation of the bronze figure.

• If you walk outside and the temperature is 30o, will you put on a coat or a bathing suit?

Temperature Conversions figure. The figure has a volume of 225 mL. If bronze has a density of 7.8 g/mL and Jodi likes to use 90.0% of the bronze melted (she sometimes spills), how many ounces of bronze does Jodi need to melt in the preparation of the bronze figure.

• T(oF) = 1.8 T(oC) + 32

• T(oC) = [T(oF) – 32] / 1.8

• T(K) = T(oC) + 273.16

• If I set my thermostat at 72 figure. The figure has a volume of 225 mL. If bronze has a density of 7.8 g/mL and Jodi likes to use 90.0% of the bronze melted (she sometimes spills), how many ounces of bronze does Jodi need to melt in the preparation of the bronze figure.oF, what will the temperature be in Celsius?

• A 4-year-old child has a temperature of 38.7 which her temperature had dropped to 20.6oC. Since high fevers cause convulsions in children, it is recommended that Phenobarbital be given if the temperature exceeds 101.0oF. Should Phenobarbital be given now?

Temperature vs Heat which her temperature had dropped to 20.6

• Temperature measures average energy

• Heat measures total energy