Scientific & Chemical Foundations The Scientific Method Matter : Classification & Properties Mathematics / Arithmetic: Exponents, Significant Figures Measurement & Units: (SI & metric) Conversions and Relationships: Density, Percent VOCABULARY: Key Terms © Copyright 1998-2000 R.J. Rusay

Steps in the Scientific Method 1. Observations - quantitative - qualitative 2. Formulating hypotheses - possible explanation for the observation 3. Performing experiments - gathering new information to decide whether the hypothesis is valid

Properties & States of Matter Physical vs. Chemical Properties Solid (s), Liquid (l), Gas (g) Homogeneous vs. Heterogeneous Mixtures Organization of atoms/molecules: atoms/elements -> molecules/compounds Extensive vs. Intensive Properties © Copyright 1998-2000 R.J. Rusay

Organization of Matter

States of Matter

Physical & Chemical Properties

Types of Mixtures Mixtures have variable composition of two or more components. A homogeneous mixture is a solution (for example, vinegar: water + acetic acid, or steel & bronze: solid metals) A heterogeneous mixture is, to the naked eye, clearly not uniform (for example, a bottle of ranch dressing with two layers: water + oil, or two solids: iron and sulfur)

Compounds & Elements Compound: A substance with a constant composition that can be broken down into elements only by chemical processes,eg. FeS, Iron (II) sulfide Element: A substance that cannot be broken into simpler substances by chemical means, eg. Fe, Iron or S8 Sulfur

Measurement & Units Qualitative vs. Quantitative MASS (Chem: gram; SI: kg) LENGTH (Chem: cm & others; SI: m) TEMPERATURE (Celsius & Kelvin; SI: K) VOLUME (Chem: mL; SI: Liter) CHEMICAL AMOUNT: Mole (mol) (Common Units in General Chemistry) © Copyright 1998-2000 R.J. Rusay

Nature of Measurement Measurement - quantitative observation consisting of 2 parts Part 1 - number Part 2 - scale (unit) Examples: 20 grams 6.63   Joule seconds

Units of Measure

Powers of Ten: Exponents Scale: Macroscopic vs. Microscopic Video: http://www.wordwizz.com/imagendx.htm http://www.designlab.ukans.edu/~miller/pof10/CIndex.html Language can describe scale (prefixes) Relationship to Scientific Notation

Shorthand Prefixes

Mass and Volume Measurement

Liquid Measurement Tools

Volume

Temperature Scales Relative to Water

Temperature

Precision & Accuracy

Numbers Numeric expression is relative to the method of measurement. How many numbers to include? Consider: Quantitative (exactness) vs. Qualitative Short Hand expression: Scientific Notation © Copyright 1998-2000 R.J. Rusay

Significant Figures Nonzero integers always count as significant figures. 3456 has 4 sig figs. In scientific notation?

Significant Figures Exact numbers (conversion factors) can have an infinite number of significant figures. 1 liter = 1,000. ml, exactly 1 inch = 2.54 cm, exactly

Zeros - Leading zeros do not count as significant figures. 0.0486 has 3 sig figs. Number expressed in scientific notation?

Zeros Captive zeros always count as significant figures. 16.07 has 4 sig figs. Number expressed in scientific notation?

Zeros Trailing zeros are significant only if the number contains a decimal point. 9.300 has 4 sig figs. Number expressed in scientific notation?

Mathematics & Arithmetic Addition/Subtraction...... Multiplication/Division..... What is “significant”?.....Rounding Off http:dbhs.wvusd.k12.ca.us/SigFigsFable.html © Copyright 1998-2000 R.J. Rusay

Computational Rules Addition/Subtraction: Answer expressed to the least number of decimal places of the figures in the process Multiplication/Division: Answer expressed to the least number of significant figures © Copyright 1998-2000 R.J. Rusay

Conversion Factor Method (Dimensional Analysis) Use numbers and “scale factor” UNITS A Bookkeeping Method: Example ___ ft___in --------> ? m (1 ft = 12 in; 2.54 cm = 1 in; 100 cm = 1 m) ___ft x 12 in/ft + ___in = ___in ___in x 2.54 cm/in x 1 m/100cm = ___m © Copyright 1998-2000 R.J. Rusay

Density Density = Mass / Volume Units = g/mL or g/cm3; g/L Least dense man made solid substance: Aerogel, D = 3.025 x 10-3 g/cm3 Dair = 1.22 x 10-3 g/cm3 (1.22 g/L) Densest known substance: white dwarf 1 teaspoon = 3.0 T; D = ? g/cm3 (1 tsp = 14.8 mL; 1 mL = 1 cm3 ) © Copyright 1998-2000 R.J. Rusay

Percent A comparison based on normalization to 100. George Washington University: 64 unsealed addressed envelopes with $10 in each were dropped on campus in different classrooms. In economics 18 of 32 were mailed, in business, history and psychology 10 of 32 were mailed. What is the percent for each of the 2 groups of students? © Copyright 1998-2000 R.J. Rusay

Percent Continued The Professor conducting the study received 43.75% of the $640 in the mail. How much did he receive? How many of you would mail the envelop presuming no one knows you found it? One student mailed an empty envelop with the return address: Mr. IOU, 1013 Indebted Lane, Bankrupt City, MS (WSJ 1/18/95) © Copyright 1998-2000 R.J. Rusay