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Review and Introductory Topics

Review and Introductory Topics. Measurements. In science, System Internationale (SI) is used. See Table 2-2 for prefixes Giga through pico (some examples) 1Gm=10 9 m 1km=10 3 m 1mg=10 -3 g or 1000mg= 1g 1cm=10 -2 m or 100 cm = 1m. Base Units. time in seconds (s)

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Review and Introductory Topics

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  1. Review and Introductory Topics

  2. Measurements • In science, System Internationale (SI) is used. • See Table 2-2 for prefixes • Giga through pico (some examples) • 1Gm=109m 1km=103m • 1mg=10-3g or 1000mg= 1g • 1cm=10-2m or 100 cm = 1m

  3. Base Units • time in seconds (s) • length in meters (m) • mass in kilograms (kg) [base unit] • amount of substance in moles (mol) • Derived units- combinations of units • Liters (1dmx1dmx1dm) or 1dm3 • Grams/mL or newtons/m2

  4. Density • Also a derived unit • See practice problems p.29 and Appen. A p.871

  5. Temperature Scales Celsius and Kelvin used in Science. Have diff. frz. Pts and blg. Pts. Celsius: Frz/Mlt pt. of water is 00 C (320F) Boiling pt. water is 1000C (2120 F) K= 0C + 273

  6. Lab Safety • See page 16 in text • In class activity • Big ideas: • Use common sense, follow directions • No horseplay • No eating, drinking, sitting on floor or lab tables. (Chemicals or broken glass possible) • GOGGLES if using heat, chemicals, or glass.

  7. Scientific Method • Systematic way to solve problem or find an answer. • Observation( Previous info or phenomena noticed) • Hypothesis • Experiment (Testing of hypothesis) • Conclusions • Re-theorizing, re-experiment,etc.

  8. Qualitative data: descriptive in nature [Sulfur is a yellow metal, copper is an orange metal] Quantitative data: numerical in nature Aluminum has a density of 2.7g/ml Independent variable: condition or quality that can be changed. Dependent variable: what changes as a result of changing the independent variable. Terms

  9. These variables can be used for graphing. Indep. on x, dependent on y. • Control: a standard for comparison, usually set up with no change made.(or the “normal” condition) • Model: 1st level of “scientific” or idea tested. • Theory: after a model is tested many times • Scientific Law: no exceptions ever found.

  10. Scientific Notation • Method of rewriting a number as a number between 1 and 9.99 AND correct power of 10. • Ex. 215= 2.15x102 or • 0.000048= 4.8x10-5 • Change sci. not’n to standard not’n. 1.53x104m 5.66x10-3cm • To add or subtract, change all to same power of ten, then add or subtract. (Not done much)

  11. Multiplying and dividing with sci. notation • Multiply number portion, then add powers of ten. • Divide number portion, then subtract powers when dividing. P. 33 • These are used a lot in Chem.

  12. Dimensional Analysis • Uses conversion factors to convert units to other units. • Numerator must equal value of denominator. • Units cancel by algebra in numerator and denominators. See p.34-35.

  13. Accuracy and Precision • Accuracy: how close a measured value is to accepted value.(Arrow and target) • Precision: how close a set of measurements are to each other. • Discuss fig 2-9, on p.36 • It is possible to be precisely wrong.

  14. %Error • A comparison of an experimental value to the true value. • Practice problems p. 38, p. 871

  15. Significant Figures • Significant figures is a method of expressing amount of exactness reflected in a measurement. • More significant figures, more exact a number is. • Rules for determining sig. digits and for calculating with them must be followed. • P. 39 recognizing, p.40 rounding, p.41 add/subtract, p.42 mult./division

  16. SIGNIFICANT Zeroes between non zeroes, (captive), 403 All nonzero digits, 321 Zeroes after decimal and at very end. 4.5600 NOT SIGNIFICANT Placeholding zeroes, 0.0023 4700 150 Sci. notation will eliminate non sig. 0’s Determining Sig. Digits

  17. Graphing • Visual display of data • Line graphs mostly used • Indep. var. on x, dep. on y • Slope sometimes used • + slope means direct proportion • - slope means inverse proportion.

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