Chapter 2

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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

Scientific Notation
• 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
Measurement
• 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.
Significant Figures
• The number of digits that are known accurately plus the doubtful digit for a measurement.
Significant Figures
• 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
• Exact numbers have an unlimited number of significant figures.
• 1 dozen = 12 = 12.00 = 12.00000000
Calculations
• 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

You have just won 2410 nickels in Las Vegas. How many quarters can you get to play with?
SI Units (Metric system)
• Mass kilogram
• Length meter
• Temperature Kelvin
• Time second
Convert 4.6 cm to nm.
• Convert 750 ml to L.
A glass of orange juice contains 0.85 dL of juice. How many milliliters of orange juice is that?
• The recommended daily allowance of phosphorus for an adult male is 800 mg. How many grams of phosphorus are recommended?
• A hummingbird has a mass of 0.55 kg. What is the mass of the hummingbird in grams?
Squared and cubic units
• 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?
A person is 60.0 in tall. What is this height in cm?
• If someone weighs 80.7 kg, how much is this in pounds?
The daily dose of ampicillin for the treatment of an ear infection is 115 mg/kg body weight. What is the daily dose for a 34-lb toddler?
A person on a diet has been losing weight at the rate of 3.5 lb. per week. If the person has been on the diet for 6 weeks, how many kilograms were lost?
A plastics manufacturing plant uses 3.3 tons of oil per week. If oil costs \$4.65/kg, how much will 1 years worth of oil cost the plastics manufacturer?
Density
• 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.
A bottle containing 325 g of cleaning solution has fall and broken on the floor. If the solution in the bottle has a density of 0.850 g/mL, what volume of solution needs to be cleaned up?
A fish tank holds 30.0 gal of water. Using a density of 1.0 g/mL for water, determine the number of pounds of water in the fish tank.
A sample of sugar weighing 2.47 g contains 0.988 g of carbon. What is the % carbon in sugar?
An introductory chemistry class began with 135 students. Of the original enrollment, 11.1 % received a final grade of A. How many students earned an A?
Water is composed of 11.2% hydrogen and 88.8% oxygen. What mass of water contains 15.0 g of oxygen?
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
• If you walk outside and the temperature is 30o, will you put on a coat or a bathing suit?
Temperature Conversions
• T(oF) = 1.8 T(oC) + 32
• T(oC) = [T(oF) – 32] / 1.8
• T(K) = T(oC) + 273.16
A young woman recovered from extreme hypothermia, during which her temperature had dropped to 20.6oC. What was her temperature on

a. the Fahrenheit scale

b. the Kelvin scale

A 4-year-old child has a temperature of 38.7oC. 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
• Temperature measures average energy
• Heat measures total energy