HTML University

Science Dept.

Chemistry CHE 100 Notes
B. Introduction

1. Mass and Weight
   1. Mass is the amount of matter

   2. Weight is the Force of Attraction on that mass in a gravitational field

   3. Force or Weight = G m₁m₂ / R²

   4. For example: A mass that would have 100 lbs on the earth would have 16.9 pounds on the moon

   5. In the British System we usually measure weight in pounds and not mass in slugs

   6. In the metric or SI system we usually measure mass in grams and not weight in newtons

2. Metric System
   1. Kilo ... 1000 ..................................... 10³
   2. Deci ... 1/10 ............... 0.1 ............... 10^-1
   3. Centi .. 1/100 ............. 0.01 ............. 10^-2
   4. Milli .... 1/1000 .......... 0.001............ 10^-3
   5. Micro . 1/1000.000 ... 0.000001 ...... 10^-6

3. Exponents and Scientific Notation
   1. 1 x 10⁰ = 1
   2. 1 x 10¹ = 10
   3. 1 x 10² = 100
   4. 1 x 10³ = 1000

   5. 1 x 10^-1 = 1/10¹ = 1/10
   6. 1 x 10^-2 = 1/10² = 1/100
   7. 1 x 10^-3 = 1/10³ = 1/1000

   8. 2 x 10³ x 3 x 10⁴ = 6 x 10⁷
   9. 2 x 10³ x 3 x 10^-4 = 6 x 10^-1
   10. 6.0 x 10³ x 3.0 x 10⁴ = 1.8 x 10⁸

   11. 8 x 10³ / 2 x 10² = 4 x 10¹
   12. 6 x 10² / 3 x 10^-4 = 2 x 10⁶

4. Units and Conversions
   1. Many of the conversions, but not all, in this course can use the form:
      (What you know) x (Relationship Fraction) = (What you need)
      Pay particular attention to the labels!

   2. For Example:
      Let us change from kilograms to grams.
      We already know that 1000 grams = 1 kilogram.
      

      (1 kilogram) x (Relationship Fraction) = (______grams)

      (1 kilogram) x (____grams/kilograms) = (______grams)

      N.B. Please Note that the kilograms label cancels out!

      (1 kilogram) x (1000 grams/kilogram) = (1000 grams)

   3. Try the Conversion of 200 milligrams to kilograms. Do this in two steps, mg to g and then g to kg.

5. Energy...the Capacity to do Work
   1. Energy and Work use the same units, Force x Distance
      In British Units it is stated as feet x pounds or foot-pounds.
      In SI or metric it is stated as newtons x meters or newton-meters. And one newton-meter is called one joule.

   2. Types of Energy:
      Mechanical or kinetic...Electrical...Chemical...Potential... Heat...Light...Sound.

   3. Energy can be transformed from one kind to another... for example from electrical to light. When that happens some of this energy become unusable, eg as heat. This Entropy has serious consequences for the entire universe.

   4. Energy is measured in joules (newton-meters) and heat energy can be measured in joules and calories.

6. Temperature
   1. Item: Heat flows from a hot body to a cold one.

   2. Definition: Temperature is the degree of hotness. At Absolute Zero (0^oK or -273.14^oC) there is no heat and no molecular motion.

   3. Relationships
      1. Boiling Point (water).....212^oF.......100^oC.......373.14^oK
      2. Freezing Point................32^oF............0^oC.......273.14^oK
      3. Absolute Zero.........................-273.14^oC................0^oK

   4. Conversion from Fahrenheit to Celsius: (^oF - 32) x 5/9 = ^oC
      1. Example for 68^oF: (68^oF - 32) x 5/9 = 20^oC

   5. Conversion from Celsius to Fahrenheit: (^oC x 9/5) + 32 = ^oF
      1. Example for 20^oC: (20^oC x 9/5) + 32 = 68^oF

   6. Conversion from Celsius to Kelvin: ^oC + 273.14 = ^oK

   7. Conversion from Kelvin to Celsius: ^oK - 273.14 = ^oC

7. Specific Heat
   1. Definition: the amount of heat needed to raise 1 gram of the substance 1^oC.

   2. For water: 1 calorie per gram degree. For Al : 0.217 calories per gram degree

   3. Definition of the calorie: The amount of heat needed to raise one gram of water from 14.5^oC to 15.5^oC.

   4. See also: the Molar Heat of a substance (in calories as well as joules).

8. Density
   1. Density = mass/volume

9. Specific Gravity
   1. Sp. Gr. = (density of the substance)/(density of water at 4⁰C).......this is one of the few dimensionless numbers.

10. Problem to Solve
    1. In the Los Angeles area, at one time in the past, 10 tons of Pb/day was deposited near roads from auto exhausts. How many kg/yr? N.B. 1 ton = 2000 lbs. N.B. 1 lb = 0.454 kg. N.B. 1 yr = 365.25 da.

11. How About a Quick Quiz?