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# Lecture 3.2 through 3.4- Units, Conversions, & Density

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Section 3.2 through 3.4 Lecture for Honors & Prep Chemistry

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• The two parts of a conversion factor, the numerator and the denominator, are equal.
• In this computer image of atoms, distance is marked off in nanometers (nm). Inferring What conversion factor would you use to convert nanometers to meters?
• A 10-g sample of pure water has less volume than 10 g of lithium, but more volume than 10 g of lead. The faces of the cubes are shown actual size. Inferring Which substance has the highest ratio of mass to volume?
• Because of differences in density, corn oil floats on top of corn syrup.
• ### Lecture 3.2 through 3.4- Units, Conversions, & Density

1. 1. Bellwork- sig figs Honors only For full credit you must… How many sig figs? 1) 1000g 6) 1000g = 1kg 2) 1000.0g 7) 1000 people 3) 0.000110g 8) 1.1m + 11.11m +1.111m = 4) 1.1 x 10-4g 9) 11m x 101m = 5) 10,101g
2. 2. Lecture 3.2- Units
3. 3. 3.1 Using and Expressing Measurements A measurement is a quantity that has both a number and a unit.
4. 4. Measuring with SI Units 5 of the 7 S.I. base units are used by chemists m meter (length) kg kilogram (mass) K kelvin (temperature) s second (time) mol mole (quantity)
5. 5. 3.2 Units and Quantities For very large or very small measurements, use a metric prefix.
6. 6. 3.2 Units and Quantities
7. 7. Units of Volume 3.2 Units and Quantities The SI unit of volume is the cubic meter (m)3, which is the amount of space occupied by a cube that is 1 m along each edge. A more convenient unit of volume for everyday use is the liter, a non-SI unit.
8. 8. Units of Volume 3.2 Units and Quantities The SI unit of volume is the cubic meter (m)3, which is the amount of space occupied by a cube that is 1 m along each edge. A more convenient unit of volume for everyday use is the liter, a non-SI unit. A liter (L) is the volume of a cube that is 10 centimeters (10 cm) along each edge. 10 cm × 10 cm × 10 cm = 1000 cm3 = 1 L
9. 9. 3.2 Units and Quantities Common metric units of volume include the liter, milliliter (aka cubic centimeter), and microliter.
10. 10. 3.2 Units and Quantities Common metric units of mass include kilogram, gram, milligram, and microgram.
11. 11. 3.2 Units and Quantities Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin.
12. 12. Absolute zero = lowest possible temperature
13. 13. 3.2 Units and Quantities 1 C° = 1 K
14. 14. 3.2 Units and Quantities
15. 15. 3.2 Units and Quantities Energy is the capacity to do work or to produce heat.
16. 16. 3.2 Units and Quantities The joule (J) is the SI unit of energy. One calorie (cal) is the quantity of heat that raises the temperature of 1 g of pure water
17. 17. BELLWORK- units Student’s Magnitude SI unit 1)Match the age 1.6 K appropriate Body 6.2 x 101 kg magnitude and temp. SI unit to the height 3.1 x 102 m item being mass 4.8 x 108 s measured. 2)Convert 32°C to Kelvins 3)Convert 250K to °C 4) Convert \$9,675,000,000,000 to scientific notation. 5) Convert 1.2x10-7m to standard notation
18. 18. Lecture 3.3- Unit conversions
19. 19. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
20. 20. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
21. 21. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
22. 22. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
23. 23. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
24. 24. A3.3 conversion factor is a fraction that is equal to one because the values in the numerator and the denominator are equal. Ex. 1g and 1000mg 1000mg 1g
25. 25. 3.3 Conversion Factors Using the relationship 1000mL = 1L, you can write the following conversion factors. 1000 ml 1L 1L 1000ml
26. 26. 3.3 Using conversion factors to change units 5,600ml
27. 27. 3.3 Using conversion factors to change units Put the units you’ve got on the bottom, so they will cancel out. Put the units you want on the top. 5,600ml x 1L 1000ml
28. 28. 3.3 Using conversion factors to change units Put the units you’ve got on the bottom, so they will cancel out. Put the units you want on the top. 5,600ml x 1L = 5.6L 1000ml
29. 29. 3.3 Using conversion factors to change units Put the units you’ve got on the bottom, so they will cancel out. Put the units you want on the top. 5,600ml x 1L = 5.6L 1000ml Because 1 L=1000ml we are really just multiplying by one and THE VALUE STAYS THE SAME.
30. 30. 3.5 Using multiple conversion factors in a row is called dimensional analysis
31. 31. 3.5 Using multiple conversion factors in a row is called dimensional analysis 8 hours GIVEN
32. 32. 3.5 Using multiple conversion factors in a row is called dimensional analysis 8 hours ? seconds GIVEN WANTED
33. 33. 3.5 Using multiple conversion factors in a row is called dimensional analysis How do I get 8 hours ? seconds GIVEN in between? WANTED
34. 34. 3.5 Using multiple conversion factors in a row is called dimensional analysis ? 8 hours seconds
35. 35. 3.5 Using multiple conversion factors in a row is called dimensional analysis 60 minutes ? 8 hours x 1 hour seconds
36. 36. 3.5 Using multiple conversion factors in a row is called dimensional analysis 60 minutes x 60 seconds ? 8 hours x = 1 hour 1minute seconds
37. 37. 3.5 Using multiple conversion factors in a row is called dimensional analysis 60 minutes x 60 seconds ? 8 hours x = 1 hour 1minute seconds 8 x 60 x 60 = 28,800 seconds
38. 38. for Sample Problem 3.7 PRACTICE! CONVERT 5670 milliseconds to seconds CONVERT 100 km/h to m/s
39. 39. Lecture 3.4- Density
40. 40. 3.4 Determining Density Density is the ratio of the mass of an object to its volume.
41. 41. 3.4 Determining Density Each of these 10-g samples has a different volume because the densities vary.
42. 42. 3.4 Determining Density Density is an intensive property that depends only on the composition of a substance, not on the size of the sample.
43. 43. 3.4 Determining Density The density of corn oil is less than the density of corn syrup. For that reason, the oil floats on top of the syrup. HIGH DENSITY on bottom LOW DENSITY on top
44. 44. 3.4 Density and Temperature
45. 45. 3.4 Density and Temperature The volume of most substances increases as the temperature increases. The mass remains the same. The density of most substances will decrease as the temperature increases.
46. 46. 3.10
47. 47. 3.10
48. 48. 3.10
49. 49. 3.11
50. 50. 3.11
51. 51. 3.11
52. 52. 3.11
53. 53. 3.3 Section Quiz Express the density 5.6 g/cm3 in kg/m3. a) 5.6 × 106kg/m3 b) 5.6 × 103kg/m3 c) 0.56 kg/m3 d) 0.0056 kg/m3
54. 54. 3.3 Section Quiz Express the density 5.6 g/cm3 in kg/m3. a) 5.6 × 106kg/m3 b) 5.6 × 103kg/m3 c) 0.56 kg/m3 d) 0.0056 kg/m3