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 m1km=10 3 m –1mg=10 -3 g or 1000mg= 1g –1cm=10 -2 m or 100 cm = 1m

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 1dm 3 –Grams/mL or newtons/m 2

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

Temperature Scales Celsius and Kelvin used in Science. Have diff. frz. Pts and blg. Pts. Celsius: Frz/Mlt pt. of water is 0 0 C (32 0 F) Boiling pt. water is C (212 0 F) K= 0 C + 273

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.

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.

Terms  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. what changes as a result of changing the independent variable.

 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: 1 st level of “scientific” or idea tested.  Theory: after a model is tested many times  Scientific Law: no exceptions ever found.

Scientific Notation  Method of rewriting a number as a number between 1 and 9.99 AND correct power of 10. – Ex. 215= 2.15x10 2 or – = 4.8x10 -5  Change sci. not’n to standard not’n. 1.53x10 4 m5.66x10 -3 cm  To add or subtract, change all to same power of ten, then add or subtract. (Not done much)

 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.

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

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.

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

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

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

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.