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Chemistry and Numbers

Chemistry and Numbers. What is Chemistry?. the study of the composition of matter and the changes it undergoes comes from the word alchemy

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Chemistry and Numbers

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  1. Chemistry and Numbers

  2. What is Chemistry? • the study of the composition of matter and the changes it undergoes • comes from the word alchemy • refers to both an early form of the investigation of nature and an early philosophical and spiritual discipline, both combining elements of chemistry, metallurgy, physics, medicine, astrology, semiotics, mysticism, spiritualism, and art all as parts of one greater force • example- making lead into gold (tomorrow’s lab- sort of) • five main areas of chemistry one can study--

  3. 1. Organic Chemistry • Organic is the study of matter that contains carbon • Organic chemists study the structure, function, synthesis, and identity of carbon compounds • Useful in petroleum industry, pharmaceuticals, polymers

  4. 2. Inorganic Chemistry • Inorganic is the study of matter that does NOT contain carbon • Inorganic chemists study the structure, function, synthesis, and identity of non-carbon compounds • Polymers, Metallurgy

  5. 3. Biochemistry • Biochemistry is the study of chemistry in living things • Cross between biology and chemistry • Pharmaceuticals and genetics

  6. 4. Physical Chemistry HONKif you passed p-chem • Physical chemistry is the physics of chemistry… the forces of matter • Much of p-chem is computational • Develop theoretical ideas for new compounds

  7. 5. Analytical Chemistry • Analytical chemistry is the study of high precision measurement • Find composition and identity of chemicals • Forensics, quality control, medical tests

  8. Scientific notation consists of two parts: • A number between 1 and 10 • A power of 10 nx 10x

  9. Examples • Given: 289,800,000 • Use: 2.898 (moved 8 places) • Answer:2.898 x 108 • Given: 0.000567 • Use: 5.67 (moved 4 places) • Answer:5.67 x 10-4

  10. Example • Given: 5.093 x 106 • Answer: 5,093,000 (moved 6 places to the right) • Given: 1.976 x 10-4 • Answer: 0.0001976 (moved 4 places to the left)

  11. Dimensional Analysis • figure what you have and where you are going • “cancel out” what you don’t want • Use conversion factors(fraction that equals one) • example: 23,532 seconds = ? hours 23,532 sec.X 1 min. X 1 hour = 1 60 sec. 60 min. • example: 7463 mm = ? meters 7463 mmX 1 m = 1 1000 mm • is your answer reasonable? 6.5 hours 7.463 m

  12. How many minutes are in 2.5 hours? Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

  13. Sample Problem • You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 1 dollar = 29 quarters X

  14. A rattlesnake is 2.44 m long. How long is the snake in cm? b) 244 cm 2.44 m x 100 cm = 244 cm 1 m

  15. Wait a minute! What is wrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min 1.4 day x 24 hr x 60 min x 60 sec 1 day 1 hr 1 min

  16. Chemistry In Action On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars’ atmosphere 100 km lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N “This is going to be the cautionary tale that will be embedded into introduction to the metric system in elementary school, high school, and college science courses till the end of time.”

  17. Precision vs. Accuracy • Precision • the exactness of a measurement • you get almost the same number every time, even if it is wrong • Accuracy • how close the measurement is to the correct answer

  18. precise accurate

  19. Percentage Error [error] accepted value % error = X 100% What is the percent error if the boiling point of water is measured at 99.2° Celsius? % error = 99.2°C- 100.0°C X 100% 100.0°C = 0.8°C X 100% 100°C = 0.008 X 100% = 0.8%

  20. sig fig video Significant Figures • the numbers that are known, plus one more number that is estimated • Significant values: • Every nonzero digit- 24.7, 0.743, 714 • Zeros between nonzero digits- 7003, 40.79, 1.503 • Zeros at the end of a number and to the right of a decimal point= 43.00, 1.010, 9.000 • Not Significant values • Leftmost zeroes acting as place holders- 0.0071, .00090 • Rightmost zeros acting as place holders- 300, 7000, 27,210

  21. Significant Figures When Calculating: • Addition and Subtraction • an answer should not be more accurate than your measurements! • the answer should be rounded to the same number of decimal places as the measurement with the least number of decimal places • 22.75 cm + 98.457 cm + 10. 1 cm • = 131.307 on your calculator • however, 10.1 cm has the least number of decimal places • therefore, the answer is 131.3 cm

  22. Multiplication and Division • an answer should not be more accurate than your measurements! • the answer should be rounded to the same number of significant figures as the measurement with the least number of significant figures • 0.7m + 98.457 m • = 68.9199 m2 on your calculator • however, 0.7 m has the least number of significant figures • therefore, the answer is 60 m2

  23. International System of Units (SI) • adopted in 1960 • seven base units which all others can be derived • m, kg, K, s, mol, cd, A

  24. Common Metric Prefixes

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