Unformatted text preview: Success in Chemistry Class Come to class. Read the chapter before lecture. Put in the time study 2 hours outside of class for every hour in lecture. Do problems everyday. Sample exercise in chapter Study problems at end of chapter, with answers (blue), without answers (black) Do not be afraid to ask for help: TA (office hours), Mrs. Splan, tutoring center. CHEMISTRY 1151 Chemical Foundations Chemistry a study of matter and the changes matter undergoes. Chemistry is an experimental science. Specific questions asked Experiments carried out Observations made Qualitative and quantitative information is collected. Chemical and physical changes are usually accompanied by a gain or loss of energy. The Scientific Method QUESTION observe nature research literature GUESS (hypothesis) yes no observations CONCLUSION MODEL predict behavior EXPERIMENT test model Scientific method definitions Sec. 1 & 2: read. hypothesis: plausible explanation for behavior of matter theory: widely tested explanation for behavior of matter (a model) fact: observation law: generalized statement of fact Chemistry: An Applied Science Health Care Building Materials Energy Daily Life: Clothing, Food, Electonics,"Toys" Classification of Matter: p. 29 text Pure Substances: Solids, Liquids, Gases Substance: 1 kind of matter Element: Composed of 1 kind of atom. cannot be broken down by chemical means Compound: Composed of 2 or more kinds of atoms, united in a definite composition by weight. can be decomposed by chemical means Physical Property: describes appearance, state or physical behavior of substance. Physical Change: change in physical property. Chemical Property: describes how a substance undergoes a chemical change. Chemical Change: change in the identity of the substance. Mixtures Heterogeneous: nonuniform Homogeneous: uniform throughout Solution: homogeneous mixture Solute: substance dissolved Solvent: substance doing dissolving Omit: pp. 2627, separating components of mixtures. Aqueous Solutions (homogeneous mixture) Quantity of solid, liquid or gas (SOLUTE) dissolved in a quantity of water (SOLVENT). MOLARITY: ratio of MOLES of solute to VOLUME of solution M = moles volume and MV = moles When solution is diluted, moles are constant therefore ratio changes according to M V = M V 1 1 2 2 Example: 50.0 mL of H O is added to 2 10.0 mL of 12 M HCl. What is the new molarity of the solution? V = 10.0 mL 1 V = 60.0 mL 2 M = 12 M, 1 M = ? 2 M = 12M (10.0 mL) = 2 60.0 mL M = 2.0 M 2 Measurement Quantitative Observations Metric Conversions: Prefixes and SI Units p. 9 12 pico (p) = 10 9 nano (n) = 10 6 micro (m) = 10 milli (m) = 0.001 centi (c) = 0.01 deci (d) = 0.1 length: meter (m) mass: kilogram (kg) temperature: kelvin (K) time: second (s) quantity of substance: mole (mol) kilo (k) = 1000 Derived Unit: Measuring Volume (fig.1.6) 1 dm 1 dm 1 dm 3 V = 1 dm = 1 liter (L) Liter box: Contains volume of 1 liter or 1000 mL KNOW!! 3 3 3 1 dm = (10 cm) = 1000 cm 3 1 L = 1000 mL = 1000 cm 3 1mL = 1 cm Metric System Problems: Transparencies Unit Conversion (FactorLabel) Problems MetricU.S. Conversions Density: density = mass/volume units: g/mL, solids and liquids units: g/L, gasses Significant Digits p.20 All nonzero digits and 0's between non zero digits (captive zeros) ARE significant. 0's in front of a number (leading) are N OT significant (placeholders). Terminal 0's to right of decimal point (trailing) ARE significant. Terminal 0's are NOT significant if there is no decimal point. Examples: Examples: 12.3 12.30 0.123 0.1230 .1230 100 100.0 100. Express 100 to 2 sig. figures Exact Numbers: Infinite Number of Sig. Figures Identities: 1 inch = 2.54 centimeters 1.00000... in = 2.5400000.....cm Counted Items Police counted 454 cars in lot. There are 450 cars in lot. (not counted) Rounding Significant Figures Multiplication and Division: round to number of significant figures as in LEAST precise term. Addition and Subtraction: round to number of PLACES BEYOND DECIMAL POINT as in term with LEAST number of places beyond decimal point. Examples: transparency Uncertainty of Measurement
Precision: How certain is the measurement? Refers to how closely measurements can be duplicated. In general: allowed to carry 1 uncertain digit Accuracy: How close measurement comes to true value. ...
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- Spring '08
- Chemistry, International System of Units, Chemical Foundations, decimal point, Chemical property