Chapter 1 and 2 Notes

Chapter 1 and 2 Notes - Introduction (Chapters 1 and 2) I....

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1 Introduction (Chapters 1 and 2) I. Review Items A. SI System of Measurements. 1. General. a. Chemistry = Study of the transformations and structure of matter and the accompanying energy changes . b. Since matter can be defined as anything possessing mass, occupying space and existing in time, the fundamental things we can measure are mass , dimension and time . The SI system is an agreed-on set of units used in making these measurements. 2. Metric prefixes-- The SI system is based on the metric system in which a fundamental unit is factored up or down by factors of ten, with prefixes used to indicate the factoring. The prefixes most used in chemistry are: a. Factors that increase a unit. Mega (M) = 1,000,000 X = 10 6 X kilo (k) = 1000 X = 10 3 X b. Factors that decrease a unit. pico (p) = 10 –12 X nano (n) = 10 –9 X micro ( μ ) = 10 –6 X milli (m) = 10 –3 X centi (c) = 10 –2 X deci (d) = 10 –1 X 3. SI unit of Mass = Kilogram (kg) = 1000 grams or 1000 g. 1 kg weighs ~2.2 lb. a. The practical unit of mass used in the laboratory is the gram (g). b. The masses of individual atoms in the gram scale is quite small (1.7x10 –24 g to 4.0x10 –22 g), therefore, a more convenient, defined unit for giving masses of individual atoms is the atomic mass unit (u, amu) = 1/12 the mass of the most abundant form (isotope) of C (C-12). 1 gram = 6.022x10 23 u or 1u = 1.66x10 –27 kg 4. SI unit of length = meter (m) = 39 in. a. Examples picometer (pm) = 10 –12 m, nanometer (nm) = 10 –9 m micron = 10 –6 m
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2 Bond distances are in the hundreds of pm’s and are usually expressed in that unit or in nm. The radius of Al = 143 pm in nm: 143 / p / m 1 / m 10 12 / p / m 10 9 nm 1 / m = 143 x 10 " 3 nm =0.143nm b. A non-SI defined unit often used in describing atomic and molecular dimensions is the Angstrom (Å) = 10 –10 m or 10 –8 cm . Radius of Al = 1.43 Å 5. SI unit of time = second (s) B. Some derived units ---combinations of mass, length and time. 1. Volume (V) = (length) 3 a. SI Unit = cubic meter = 1m 3 This is a very large unit and is not normally used b. Practical Units. Liter (L) = 10 –3 m 3 = 1 dm 3 ~ 1.06 qt milliliter (mL) = 10 –3 L = 1 cm 3 or 1 cc. 2. Density (d) = Mass Volume SI unit = kg m 3 = g L The density is a characteristic property of matter and can be used in identifying substances. a. Practical unit most used is g/mL or g/cm 3 b. Example A ribbon of Al that is 50.0 m x 100 cm x 18.0 mm has a mass of 2430 kg. Calculate the density of Al in SI units and in g/cm 3 . SI units (kg/m 3 ) Mass = 2430 kg = 2.43x10 3 kg Volume = 50.0 m x 100 cm 1m 100cm " # $ % x 18.0 mm 1m 1000mm " # $ % = 0.90 m 3 Density = 2.43x10 3 kg/0.90 m 3 = 2.7x10 3 kg/m 3 Density in g/cm 3 = 2.7x10 3 kg/m 3 (10 3 g/kg) (1m 3 /10 6 cm 3 ) = 2.70 g/cm 3 3. Velocity (speed) = time rate of change in position. Dimension = length time SI unit = m/s Speed of light = 2.9979x10 8 m/s 4. Acceleration = time rate of change of velocity. SI unit = m/s
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This note was uploaded on 04/07/2008 for the course CHEM 1304 taught by Professor Prof.maguire during the Spring '08 term at SMU.

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Chapter 1 and 2 Notes - Introduction (Chapters 1 and 2) I....

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