Chem 121-- Chapter 1

Chem 121-- Chapter 1

1. 1. 1 Modern Chemistry: A Brief Glimpse

   • Chemistry: The study of composition and structure of materials and of changes that materials undergo.

2. 1.2 Experiment and Explanation

   • Experiment: An observation of natural phenomena carried out in a controlled manner so that the results can be duplicated and rational conclusions obtained.
   • Law: A concise statement or mathematical equation about a fundamental relationship or regularity of nature.
     • Hypothesis: A tentative explanation of some regularity of nature.
     • Theory: A tested explanation of a basic natural phenomenon.
   • Scientific Method

3. 1.3 Law of Conservation of Mass

   • Matter: Whatever occupies space and can be perceived by our senses.
     • Mass: The quantity of Mass in a material
   • Law of Conservation of Mass: The total mass remains constant during a chemical change (chemical reaction)
     • EXAMPLE 1.3 You heat 2.53 g of metallic mercury in the air which produces 2.73 g of red-orange residue.  Mercury+Oxygen >>>>Red-orange residue What is the mass of oxygen that reacts?  First, you apply the law of conservation of mass to this reaction. The total mass remains constant during a chemical reaction.  Mass of substances before reaction=Mass of substances after reaction.  SO Mass of Mercury+Mass of oxygen= Mass of red-orange residue 2.53 grams (Mercury) + Mass of oxygen = 2.73 grams (red-orange residue) 2.73 grams - 2.53 grams= 0.20 grams of oxygen **** The mass of the oxygen that reacts with the mercury is 0.20 grams****

4. 1.4 Matter: Physical State and Chemical Constitution

   • Solid: Characterized by rigidity; fixed volume and fixed shape
     • Liquid: Relatively in compressible fluid; fixed volume, no fixed shape.
     • Gas: Compressible fluid; no fixed volume, no fixed shape.
     • The States of Matter
   • Physical Change: A Change in the form of matter but not in its chemical identity.
     • EXAMPLE Melting Dissolving: You can dissolve sodium chloride (table salt) in  water. 
     • Chemical Change/ Chemical Reaction: A change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter.
       • EXAMPLE Rusting Burning
       • Chemical property: A characteristic of a material involving its chemical change
         • EXAMPLE Ability to react with oxygen. Ability to react with fluorine. 
     • Physical Property: A characteristic that can be observed for a material without changing its chemical identity
       • EXAMPLE Physical State Boiling Point Color
   • Element: A substance that cannot be decomposed into simpler substances by any chemical reaction.
     • EXAMPLE Hydrogen Carbon Oxygen
     • Compound: A substance composed of two or more elements chemically combined
       • EXAMPLE Italian Salad Dressing Salt water
       • Mixture: A material that can be seperated by physical means into two or more substances. >>>Heterogenous and Homozygous mixtures
         • Heterogenous Mixture: A mixture that consists of physically distinct parts, each with different properties. (Salt and Iron fillings, Oil and Vinegar) Homogenous Mixture: A mixture that is uniform in its properties; also called a solution (saltwater, air)
         • Phase: One of several different homogenous materials in the portion of matter under study.

5. 1.5 Measurement and Significant Figures

   • Measurement: The comparison of physical quantity with a fixed standard of measurement---- a unit.
     • Precision: The closeness of the set of values obtained from repeated measurement to its value.
     • Accuracy: The closeness of a single measurement to its true value

6. 1.6 SI Units

   • Significant Figures
     • SF in Multiplication and Division
       • Your answer should have the same number of Significant Figures as are in the measurement with the least number of significant figures. 
     • SF in Addition and Subtraction
       • Your answer should have the same number of decimal places as are in the measurement with the least number of decimal places
     • Exact number: A counted number or defined number
     • Rounding: The procedure of dropping nonsignificant digits and adjusting the last digit reported in the final result of a calculation
       • Rounding Procedure: 1. Look at the leftmost digit to the dropped. 2. If this digit is 5 or greater: Add 1 to the last digit to be retained. Drop all digits farther to the right.  3. If this digit is less than 5. Drop all digits farther to the right. 
   • SI Units: An international system of units made up of a particular choice of metric units
     • Temperature: A measure of "hotness." Heat flows from an area of higher temperature to an area of lower temperature
       • Celsius C
       • Fahrenheit F
       • Kelvin K
   • Base Units: The seven metric units from which all other units can be derived
     • SI Base Units: Length_Meter_m Mass_Kilogram_kg Time_Second_s Temperature_Kelvin_K Amount of substance_mole_mol Electric Current_ampere_A Luminous Intensity_candela_cd
     • Selected Prefixes Mega 10^6 M Kilo 10^3 k Deci 10^-1 d Centi 10^-2 c Milli 10^-3 m Micro 10^-6 u (mew) Nano 10^-9 n Pico 10^-12 p

7. 1.7 Derived Units

   • Derived Units: Combinations of fundamental units
     • Area= length*length= m^2 Volume= length*length*length=m^3 Density Speed Acceleration Force Pressure Energy
     • Density= m/v
       • solids= g/cm^3 liquids=g/mL gases= g/L

8. 1.8 Units and DImensional Analysis

   • Factor-Label Method: A method of calculations in which one carries along the units for quantities
     • Conversion Factor: A factor equal to 1 that converts a quantity expressed in one unit to a quantity expressed in another unit.

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