Scientific Measurement

1. Ch 2 Chemistry is a lot of math! Scientific Measurement

2. Name Per, Row Warm-ups 1. 2. 8/22/13 8/26/13 Saving paper is always good!

3. Warm up • Name 3 tools used for measurement. • What is a unit? • Give an example of a unit. • Why are units important.

4. Ch 2.2 Making Measurements • Qualitative measurements:Give results in a descriptive and non-numerical form • Example: Cookie Monster is Blue • Quantitative measurements:Give results in a definite form – usually as numbers and units • Example: Cookie Monster ate 1 kg of cookies

5. Qualitative or Quantitative? • The Big Mac is $2.29. • The Pop Rocks are blue. • The coffee is hot. • The slurpee is 0 degrees Celsius.

6. Measurement—a quantity that has both a number and a unit. • For example… • I weigh 90! • I make 1000 an hour! • There are 72 in this class. • Numbers with NO units mean NOTHING…and will be marked WRONG on HW/Tests, etc. • Measurements are fundamental to the experimental science.

8. International System of Units

9. SI Units (SystemeInternationale) • Meter (m) for lengthUse a meterstick to measure • Kilogram (kg) for mass (1 kg = 2.2 lbs) • Weight is NOT the same thing as mass! • Use a scale to measure • Kelvin (K) for temperature • K = oC + 273 • 0 K = absolute zero • Use a thermometerto measure • oC is another option, but not Fahrenheit (in the metric system) • Second (s) for time • Use astopwatchto measure • Mole for the amount of substance • We will talk about mole later • Liter (L) or m3 for volume • Use a graduated cylinder to measure 1L = 1m3 • joule or calorie for energy • We don’t discuss this much in this class…

10. Mass vs Weight • Weight: measure of gravitational pull • Mass: amount of matter • - Gravity does not affect mass

11. Derived Units: it is a combination of units • Volume: cm3 • amount of space occupied by an object • Density: D= m/v • Ratio of mass to volume Speed: meters/ second

12. Warm-up A scientist wants to conduct an experiment measuring the effect of temperature on the density of nitrogen gas. What is the independent variable in this experiment? The dependent variable? What could be used as a control group? What would be some constants? What units should be used for temperature and density? What tools should be used to measure temperature and density?

13. Metric Prefixes • Adding prefixes, gives us a range of size measurements. • Based on a system of 10’s (decimal system) • NOTE that the bigger number goes with the smaller unit. • 100cm = 1 m • Prefixes you need to memorize… • milli- (1/1000), centi-(1/100), kilo-(1000x)

14. Metric prefixes: • The metric system utilizes prefixes based on powers of 10. • Prefixes you need to memorize… • milli- (1/1000x), centi-(1/100x), • kilo-(1000x)

15. All metric units increase or decrease by a power of 10.

16. Conversion factors: a ratio of equal proportions • Values can often be expressed in more than one form • $1 = 4 quarters = 10 dimes = 20 nickels = 100 pennies • 1 meter = 100cm = 1000mm = 0.001km • equal values can be shown as a ratio equal to 1; such ratios are called conversion factors… • conversion factors are useful for solving problems in which given measurements must be expressed in some other unit.

17. Example 1: conversions a. convert 20 meters to to millimeters 1. which is smaller? 2. how many of the smaller are in the larger? 3. create a conversion 1000 mm in 1m 20,000mm

18. Example 2: conversions b. Convert 20 meters to kilometers 0.02 km

19. Date SI Unit Practice Convert each of the following: 1. 3.68 kg = __________ g 2. 568 cm = __________ m 3. 8700 ml = __________ l 4. 25 mg = __________g 5. 0.101 cm = __________ mm 6. 250 ml = __________ l 7. 600 g = __________ kg 8. 8900 mm = __________ m 9. 0.000004 m = __________ mm 10. 0.250 kg = __________ mg 1000g 1 kg Example: 3.68kg * = 3680g 3.68kg * 103 Use table 2 on pg35! However you won’t get the table for your quiz next class

20. Date: SI Unit Practice What SI unit would you use to measure…. • The length of a football field? • The WIDTH of a strand of hair? • The mass of an elephant? • The mass of an ant? • The distance from school to Sears? • The height of your desk? • The volume of water in a pool? • The volume of water in a spoon? • The temperature of this room?

21. 1. 3.68 kg = __3680____ g 2. 568 cm = ___5.68___ m 3. 8700 ml = ___8.7____ l 4. 25 mg = __0.025___ g 5. 0.101 cm = ___1.01___ mm 6. 250 ml = __0.25_____ l 7. 600 g = ___0.6____ kg 8. 8900 mm = ___8.9____ m 9. 0.000004 m = __0.004___ mm 10. 0.250 kg = __250000__ mg

22. What SI unit would you use to measure…. • The length of a football field? • The WIDTH of a strand of hair? • The mass of an elephant? • The mass of an ant? • The distance from school to union station? • The height of your desk? • The volume of water in a pool? • The volume of water in a spoon? • The temperature of this room? Meters Mm, um km Mg (grams) Kilometers cm kL or km3 mL or cm3 Kelvin (Celsius)

23. SCIENTIFIC NOTATION: move decimal point the number of times ex: 1*105 indicated by the power of 10. + means larger number - means smaller number • 1) 6.5*104 = • 2) 6.5*10-4 = • 3) .00035 = • 4) 35000 = Convert the following out of or into scientific notation 65000. .00065 3.5*10-4 3.5*104

24. Derived Units: it is a combination of units • Volume: cm3 • amount of space occupied by an object • Density: D= m/v • Ratio of mass to volume • mL=cm3 Speed: meters/ second

25. Density add the symbols <, >, or =to compare the blocks < < =

26. Density: D= m/v • Ex: A rock has a mass of 10 grams and a volume of 5 cm3. Calculate its density. • Units: • or 10g / 5cm3 = 2 g/cm3

27. D= m/v How can you find density from a graph? Density is the slope of the line of mass vs volume. D= m/v=slope = = y2- - y1g X2 – x1 mL rise run Ex: 11-3 g 11-3mL = 1 g/mL

28. What mineral is more dense? A, B, or C? • - A: it has greatest slope • If you put equal volumes of A and B on a balance, which would have a larger mass? • - A

29. http://www.youtube.com/watch?v=-CDkJuo_LYs

30. Density Calculations Water displacement is used to find the volume of unusual shape: measure volume of water Add an object and measure volume again Subtract the volume of object+water from volume of just water • Ex 2. The mass of 10 copper coins is 30 grams. The initial volume of water is 50mL and the volume with the coins if 55mL. Calculate the density of the copper coins. 50mL 60ml 60-50=10mL

31. Ex: 3. The density of silver is 10.0 g/cm3. If you have a sample size of 17.235 grams, what is the volume of the silver? How would temp affect density?? • As temperature increases, what happens to density? • If density deals with mass and volume… • Does temperature affect mass? Or volume?

32. Homework • Quiz! Next class • Use pg 42 #1,2 • And 881 # 1, 2, 7, 9 to study • Table on pg 35 • HW: ch. 2 section 2 pg 42 answer questions 1-6 • Pg 881 #1, 2, 7

33. The density of silver is 10.0 g/cm3. If you have a sample size of 17.235 grams, what is the volume of the silver? If you have equal volumes of B(blue line) and C (red line). Which one has a larger mass?

34. Ch 2.3 • Accuracy: • the closeness of measurements to the actual value • Precision: • The closeness of a set of measurements to each other 2 technicians measure the density of a new substance: A: 2.000, 1.999, and 2.001 g/mL B: 2.5, 2.9, and 2.7 g/mL The correct value is 2.480 g/mL Who is more accurate and who is more precise?

35. Percent Error: measure of how different your value is form the real value Value experimental – Value accepted Value accepted • Percent error = *100% The density of water at 4 oC is known to be 1.00 g/mL. Kayla experimentally found the density of water to be 1.075 g/mL. What is her percent error? Example:

36. Ch 2.3 Significant Figures • When we make quantitative measurements, we care about how good our data is. • How we do this? Significant figures Slide 1 of 6

37. Significant Figures (Sig. Figs)in Measurements… • Significant Figures: all the digits in a measurement that are known with certainty plus one estimated digit

38. Examples: 40.7 L 87009 km .00958 m 0.09 kg 85.00g 9.00000 2000 m 2000. m 3 5 Rules for Significant Figures: • Zeros b/t nonzero digits are significant • Zeros appearing in front of all nonzero are not significant • Zeros at the end of a number and the right of a decimal point are significant • Zeros at the end of a number but to the left of a decimal point, if a decimal point is there, are significant. (NOT necessarily significant if no decimal) 3 1 4 6 1 4

39. When given a number, you must be able to determine the number of sig.figs. in it. e) 6.700 x 107 = _____ All numbers in the coefficient of a # in scientific notation are significant f) 24,000,000 = _____ zeros w/out a decimal are NOT significant Perfect example of why sci.not. is so great…gets rid of insig 0’s g) 0.00000670 = _____ zeros after a decimal but with no whole # are NEVER significant. Again, use sci.not. • a) 12,389 = _____ • All non-zero #’s are significant • b) 0.452 = _____ • Zeros before a decimal are not imp unless it is part of a whole number • c) 10.26 = _____ • zeros in between #’s are significant • d) 23.000 = _____ • Zeros after a decimal are significant IF THERE IS A WHOLE #

40. Math with Sig Figs • Conversions with Sig Figs: use same number of sig figs in the original measurement • - the conversion factor is considered exact and does not count 100cm m 4.608 m * =460.8cm

41. Addition and Subtraction with Sig Figs:answer must have same # of sig figs as the number with the fewest digits to right of the decimal • 25.1g + 2.03g = • Multiplication and Division with Sig Figs: • answer must usesame # sig figs as the # with the fewest sig figs • 3.05g / 8.47mL = 27.1g 0.360g 80.0g/ 5mL = 16mL = 20mL 80.0g/ 5.0mL = 16mL

42. SCIENTIFIC NOTATION: move decimal point the number of times ex: 1*105 indicated by the power of 10. + means move to the right - means move to the left • 6.5*104 = • 6.5*10-4 = • .00035 = • 35000 = 65000. .00065 3.5*10-4 3.5*104

43. Significant Figures A. State the number of significant digits in each measurement.  1)    2804 m 2)   2.84 km 3)   5.029 m 4)   0.003068 m 5)   4.6 x 105 m  6)   4.06 x 10-5 m 7)   750 m 8)  75 m    9)   75,000 m 10)   75.00 m  11)  75,000.0 m  12)  10 cm

44. Significant Figures Practice A. State the number of significant digits in each measurement.  1)    2804 m4  2)   2.84 km3 3)   5.029 m4 4)   0.003068 m4  5)   4.6 x 105 m 2 6)   4.06 x 10-5 m3 7)   750 m2 or 3 8)  75 m   2 9)   75,000 m 2 10)   75.00 m 4 11)  75,000.0 m  6 12)  10 cm 1 or 2

45. B. Solve the following problems and report answers with appropriate number of significant digits. 1)      6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =  2)     1.6 km + 1.62 m +1200 cm =   3)     8.264 g - 7.8 g =    4)     10.4168 m - 6.0 m =   5)     12.00 m+15.001 kg=   6)     1.31 cm x 2.3 cm =   7)     5.7621 m x 6.201 m =  8)    20.2 cm / 7.41 s =   9)    40.002 g / 13.000005 g =

46. 1)      6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =  26.3 cm 2)     1.6 km + 1.62 m +1200 cm =   1.2 x 103 or 1.20 x 103 or 1203 m 3)     8.264 g - 7.8 g =    0.5 g 4)     10.4168 m - 6.0 m =  4.4 m 5)     12.00 m+15.001 kg=   can’t add m and kg 6)     1.31 cm x 2.3 cm =   3.0 cm2 7)     5.7621 m x 6.201 m =  35.73 m2 8)    20.2 cm : 7.41 s =   2.73 cm/s 9)    40.002 g : 13.000005 g = 3.0771

47. Warm up • What tool would you use to measure mass? • What unit would you use to measure mass? • What tool would you use to measure volume? • What unit(s) would you use to measure length?

48. 1. Linear Measurements • The length, width, or height of something • Tool? • ruler, meter stick, etc. • Units? • Meter (m) • Centimeters (cm) • Millimeters (mm)

49. Practice:

50. 2. Volume • The space matter takes up • Tool? • Graduated cylinder, beaker, etc. • Units? • Liter (L) • Milliliters (mL) • cm3 • MUST BE EYELEVEL TO MEASURE CORRECTLY!