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One Last Chapter 2 Thing

Mixture. Pancake Batter, Orange Juice, Cement. Solution. Syrup, Apple Juice, White Gold (mixture of Au and Pt atoms). One Last Chapter 2 Thing. Solutions are mixtures, but not all mixtures are solutions. Think of it this way: solutions (to anything!) are special. Physical Quantity.

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One Last Chapter 2 Thing

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  1. Mixture Pancake Batter, Orange Juice, Cement Solution Syrup, Apple Juice, White Gold (mixture of Au and Pt atoms) One Last Chapter 2 Thing Solutions are mixtures, but not all mixtures are solutions. Think of it this way: solutions (to anything!) are special.

  2. Physical Quantity Name of Unit Symbol Length meter m Mass kilogram kg Time second s Temperature kelvin K Number of objects mole mol Luminous intensity candela cd Electric current ampere A The Basic Units

  3. Those units are not the only rational choice.

  4. Compound Units • Velocity is a compound unit: distance over time: m/s or m-s-1 • Force is another: mass times acceleration: kg-m/s2 = 1 Newton • Pressure is yet another: • force over area = mass times acceleration over area • = (kg-m/s2)/m2 = Newton/m2 = Pascal • There are many more (viscosity: g-cm-1s-1 = Poise)

  5. Prefix Symbol Meaning femto- F 10-15 = 1/1,000,000,000,000,000 pico- P 10-12 = 1/1,000,000,000,000 nano- N 10-9 = 1/1,000,000,000 micro- m 10-6 = 1/1,000,000 milli- m 10-3 = 1/1,000 centi- c 10-2 = 1/100 deci- c 10-1 = 1/10 kilo- k 10+3 = 1000 mega- M 10+6 = 1,000,000 giga- G 10+9 = 1,000,000,000 tera- T 10+12 = 1,000,000,000,000

  6. What is the gravitational acceleration in cgs units?

  7. One Unity = 1 2.54 cm = 1 inch [2.54 cm/1 inch] = 1 = [1 inch/2.54 cm]

  8. Compute the length of a football field in centimeters.

  9. Compute the volume of rain, in gallons, that fell a football field (100 yards long x 50 yards wide) if the weather guy said we got one inch of rain.

  10. Break: Today’s Announcements • Monday, September 10 announcements • We are maybe one day behind—not bad, considering! • Ch 2 notes are essentially in final form. • New Appendix ABC notes are available. • Watch for a take-home exam to appear on website “soon” • You should have completed many of the assigned Ch. 2 problems.

  11. Estimate the pressure on your feet when you stand up.  Express the answer in pounds per square inch, and in nt/m2.

  12. Estimate the pressure when you sit on your xxxx, in pounds per square inch, and in nt/m2.

  13. Temperature: who the heck was Fahrenheit K = oC + 273.15 oF = 32 + 1.8oC oC = (oF - 32)/1.8

  14. Convenient Temperature Conversions Summer in Duluth Body Temp. (Humans) Winter in DuluthRectal temperature of the cow Room TemperatureLiquid N2   16 oC = 61 oF 98.6 oF = 37 oC -40 oF = -40 oC 100 oF 77 oC = 25 oC 77 K = -196.15 oC = -321oF

  15. Precision vs. Accuracy

  16. Wrong Right Why 1.867 + 2 = 3.867 1.867 + 2 = 4 Addition/Subtraction: use least precise places 1.867 + 2.000 = 4 1.867 + 2.000 = 3.867 " 1.867 x 2 = 3.734 1.867 x 2 = 4 Multiply/Divide: use smallest number of significant figures 1.867 / 2.000 = 1 1.867/2.000 = 0.9355 " S I G N I F I C A N T F I G U R E S

  17. A Lost Art—Reading Gauges 23 ± 3 For sure 23 ± 1 Probably What does it read? Don’t forget to guess! What if we had to put + and – on it?

  18. Noise is Normal! • A balance that reads 1.00053 to 1.00055 is working! • A gauge that bounces around a bit is working! • (In fact, if it doesn't bounce, it might be stuck)

  19. Exponential Notation • Use it when it is EASIER. • Your calculator has an “E” button—learn how it works To code in Avogadro’s number (we’ll see this later) push 6-.-0-2-3- E-2-3.

  20. Remember the Rules!!! (6 x 1023) x (3 x 1013) = 18 x 1036 Products: Add Exponents (6 x 1023) / (3 x 1013) = 2 x 1010 Quotients: Subtract Exponents

  21. Suppose we measure a square tile, and find that each edge of the tile is L = 12.1 ± 0.2 inches. What is % uncertainty? Percent Errors

  22. What is the uncertainty in the area of the square tile? Error Propagation

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