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Foundations of Chemistry

Foundations of Chemistry. Prefixes. Tera- T 1,000,000,000,000 10 12 giga- G 1,000,000,000 10 9 mega - M 1,000,000 10 6 kilo - k 1,000 10 3 deci- d 0.1 10 -1 centi- c 0.01 10 -2 milli- m 0.001 10 -3 micro- m 0.000001 10 -6 nano- n 0.000000001 10 -9

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Foundations of Chemistry

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  1. Foundations of Chemistry

  2. Prefixes • Tera- T 1,000,000,000,000 1012 • giga- G 1,000,000,000 109 • mega - M 1,000,000 106 • kilo - k 1,000 103 • deci- d 0.1 10-1 • centi- c 0.01 10-2 • milli- m 0.001 10-3 • micro- m 0.000001 10-6 • nano- n 0.000000001 10-9 • pico- p 0.000000000001 10-12

  3. Prefixes • Tera- T 1,000,000,000,000 1012 • giga- G 1,000,000,000 109 • mega - M 1,000,000 106 • kilo - k 1,000 103 • deci- d 0.1 10-1 • centi- c 0.01 10-2 • milli- m 0.001 10-3 • micro- m 0.000001 10-6 • nano- n 0.000000001 10-9 • pico- p 0.000000000001 10-12

  4. Mass • is the amount of matter in an object. • Tool - balance scale • Standard SI unit – kilogram • Base unit - gram • Common units = mg,mg, g, kg • Weight – pull of gravity on matter

  5. Length • The distance between two points • Tool – metric ruler • Standard unit - meter • Common units – mm, cm, m, km

  6. Derived Units • Many SI units are combinations of base units called derived units • Examples we will use at this time are volume and density

  7. Volume • The amount of space an object occupies • V = L x W x H • Tools – metric ruler, graduated cylinder, buret, volumetric flask • SI unit - m3 • 1 Liter = 1 dm3 • 1 mL = 1 cm3 = 1 cc

  8. Using Scientific Measurements • All measurements have a certain degree of uncertainty • Uncertainty can result in limitations that depend on the instrument or the experimenter • Scientists use two word to describe how good the measurements are

  9. How good are the measurements? • Accuracy- how close the measurement is to the actual value • Precision- how closely the numerical values of a set of measurements agree with each other • Random error - equal chance of being high or low- addressed by averaging several measurements • Systematic error- same direction each time, they can be compensated for

  10. Percent Error Accuracy is judged using percent error. The formula is: Actual Value – Experimental Value x 100 Actual Value

  11. Significant figures (sig figs) • Scientists record measurements in significant figures. • Sig figs consist of all the digits known with certainty plus a final digit that is estimated.

  12. Rules for Determining Sig Figs • All nonzero digits are significant • Exact numbers (from counting or definitions) do not limit sig figs • All zeros between nonzero digits are significant

  13. Atlantic/Pacific Rule for Determining Sig Figs • If a decimal point is Present, count from the Pacific side • If a decimal point is Absent, count from the Atlantic Side • Begin counting with the first nonzero digit you come to and then keep counting

  14. Adding and subtracting with sig figs • Round the answer so that the estimated digit is in the same place value as the least precise measurement

  15. 27.93 + 6.4 27.93 27.93 + 6.4 6.4 For example • First line up the decimal places Then do the adding Find the estimated numbers in the problem 34.33 This answer must be rounded to the tenths place

  16. Multiplication and Division • The answer should have the same number of significant figures as the measurement with the least number of sig figs • 3.6 x 653 • 2350.8 • 3.6 has 2 s.f. 653 has 3 s.f. • answer can only have 2 s.f. • 2400

  17. Dimensional Analysis • A problem solving method that treats units in calculations as algebraic factors • Units common to both numerators and denominators are cancelled and removed from the expressions • A conversion factors is used to convert from one unit to the other • Exact conversions do not limit significant figures

  18. Density • D = M / V • An intensive property (it is unaffected by the size of the sample) • Density is often used to identify substances. • Common units - g/ cm3, g/mL, g/L • Tools? -

  19. Density • As the mass of the substance increases the volume increases proportionately and the ratio of mass to volume (density) is constant • This is a direct proportion therefore the graph is a straight line that passes through the origin.

  20. Density • Because most substances expand with an increase in temperature (increasing the volume), density usually decreases with increasing volume. • Density varies with temperature

  21. Density of water • 1 g of water is 1 mL of water. • density of water is 1 g/mL (at 4ºC) • Specific gravity - the density of an object compared to the density of water • Specific gravity of water is 1.0

  22. Chem II Quick Lab • Use the accepted density to determine the thickness of aluminum foil. • Compare your data and calculations with other students to concur and determine an average.Write a short lab report in your composition book that includes a data table. • D = m/V • D = m/ LWH • H = m/DWH

  23. Temperature • A measure of the average kinetic energy • Different temperature scales based on the same expansion of mercury. • So why are they different?

  24. Converting Between Celsius and Kelvin K = C + 273.15 C = K - 273.15 0ºC 273K 100 º C 373K

  25. Converting Between Celsius and Fahrenheit 1ºC = 9/5ºF F= 9/5ºC +32 C = 5/9 (ºF – 32) 0ºC 100ºC 212ºF 32ºF

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