1. Unit 2. Measurement
This lesson is 8 days long

2. Do Now
In your own words, what do you think is the difference between Accuracy and Precision?

3. Accuracy vs. Precision
Accuracy - how close a measurement is to the accepted value

4. Accuracy vs. Precision
Precision - how close a series of measurements are to each other

5. ACCURATE = CORRECT PRECISE = CONSISTENT

6. Percent Error Equation
The accuracy of an individual value can be compared with the correct or accepted value by calculating the percent error.
Percent Error Equation
experimental - accepted value x 100
accepted value

7. Percent Error Example: Measuring the boiling point of H2O
Thermometer reads – 99.1OC
You know it should read – 100OC
experimental - accepted value x 100
accepted value

8. % error = |99.1oC – 100.0oC| x 100%
100oC
= o C x 100%
100o C
= x 100% = 0.9%

9. Not All Errors are equal…
You fly from NY to
San Francisco
You are an eye surgeon
Your plane is blown off
course by 3cm
Your scalpel misses the mark by 3cm
They sound equal … but are they?

10. Objectives:
Describe the difference between a qualitative and a quantitative measurement.
Describe the difference between accuracy and precision.
Write a number in scientific notation.
State the appropriate units for measuring length, volume, mass, density, temperature and time in the metric system..
Calculate the percent error in a measurement.
Calculate density given the mass and volume, the mass given the density and volume, and the volume given the density and mass.

11. Units of Measurement

12. Do Now: Name the equipment and briefly describe the purpose of each.
A. B. C. D. E.

13. Measurements represent quantities.
A quantity is something that has magnitude, size or amount.
All measurements are a number plus a unit (grams, teaspoon, liters).

14. A. Number vs. Quantity
Number + Unit! … Always!

16. B. SI Units Length l meter m Mass m kilogram kg Time t second s Temp T
Quantity
Symbol
Base Unit
Abbrev.
Length l
meter m
Mass m
kilogram kg
Time t
second s
Temp T
kelvin K
Amount n
mole
mol

17. Do Now What are the SI units for…. Length: ______________
Mass: _______________
Temperature: ____________

18. B. SI Units Prefix Symbol Factor mega- M 106 kilo- k 103 BASE UNIT ---
100
deci- d
10-1
centi- c
10-2
milli- m
10-3
micro- μ
10-6
nano- n
10-9
pico- p
10-12

20. SI Prefix Conversions 1) 20 cm = ______________ m
2) L = ______________ mL
3) 45 μm = ______________ m

21. Do Now 1) .87 cm = ______________ μ m 2) 62.3 L = ______________ hL
3) 0.98 μm = ______________ nm

22. Do Now 1. 4.5nm = ___________ cm 2. 0.568hg = ____________ mg
cL = _________ μL

23. Derived SI Units
Many SI units are combinations of the quantities shown earlier.
Combinations of SI units form derived units.
Derived units are produced by multiplying or dividing standard units.

25. Scientific Notation

26. Let’s Try These 1.0 x 101 = ______________ 2.0 x 102 = ______________

27. Scientific Notation

28. A Problem worked out 23,415 = ____________________ 2.3415 X 10,000
If you go to the ….
Right = negative number in exponent
Left = positive number in exponent

29. Do Now A. 124 = _____________________________
B.   = _________________
C. 93,000,00 = ________________________
D.  3.6 × = ______________________

30. What is this called? How do you use it?
List the steps!

31. Do Now A. 3290 = _____________________________
B.   = _________________
C. 76,500,000 = ________________________
D.  4.5 × = ______________________

32. M V D = C. Derived Units cont… Density: ratio between mass and volume
kg/m3 or g/mL or g/cm3
does not depend on size of sample
D = M V

33. Volume Volume is the amount of space occupied by an object.
length x width x height
Expressed as cubic centimeter (cm3) or cubic meter (m3).
When measuring liquid volumes in the laboratory a chemist typically uses milliliters (mL)
1 mL = 1 cm3

34. How do you calculate density?
You need the measure Mass and Volume
Mass - Obtain by weighing the mass of an object by using a balance and then determine the volume.

35. How do you calculate density?
Solids - the volume can be a little difficult since it’s not a perfect shape.
If the object is a regular solid, like a cube, you can measure its three dimensions and calculate the volume.
Volume = length x width x height

36. Volume continued …
If the object is an irregular solid, like a rock, determining the volume is more difficult.
Archimedes’ Principle – states that the volume of a solid is equal to the volume of water it displaces.
Put some water in a graduated cylinder and read the volume. Next, put the object in the graduated cylinder and read the volume again.
The difference in volume of the graduated cylinder is the volume of the object.

37. Volume Displacement 25 mL
A solid displaces a matching volume of water when the solid is placed in water.
35mL
25 mL

38. Learning Check
What is the density (g/mL) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?
1) 0.2 g/mL ) 6 g/mL ) g/mL

39. PROBLEM: Mercury (Hg) has a density of 13. 6 g/cm3
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams?

40. Do Now: 1. What is the equation for density. 2
Do Now: 1. What is the equation for density? 2. What is Archimedes’ Principle ?

41. PROBLEM: Mercury (Hg) has a density of 13. 6 g/cm3
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg?
First, note that 1 cm3 = 1 mL
Strategy
Use density to calc. mass (g) from volume.
Density = Mass
Volume

42. PROBLEM: Mercury (Hg) has a density of 13. 6 g/cm3
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 cm of Hg? 3
Density = Mass
Volume
13.6g/cm3= Mass (g)3
95 cm 3

43. Do NOW- What units do we use for….. A. Volume B. Mass C. Density
*** List all that apply***
What’s the equation for density?

44. Learning Check Osmium is a very dense metal. What is its
density in g/cm3 if g of the metal occupies a volume of 2.22cm3?
1) g/cm3
2) 22.5 g/cm3
3) 111 g/cm3

45. Solution
Placing the mass and volume of the osmium metal into the density setup, we obtain
D = mass = g =
volume 2.22 cm3
= g/cm3 = g/cm3

46. Learning Check
The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane?
1) kg
2) 614 kg
3) 1.25 kg

47. Learning Check
The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane?
1) kg

48. Problem-Solving Steps
1. Analyze
2. Plan
3. Compute
4. Evaluate

49. D. Density V = 825 cm3 D = 13.6 g/cm3 M = ? GIVEN: WORK:
An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass.
GIVEN:
V = 825 cm3
D = 13.6 g/cm3
M = ?
WORK:

50. D. Density
An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass.
GIVEN:
V = 825 cm3
D = 13.6 g/cm3
M = ?
WORK:
M = DV
M = (13.6g/cm3)(825cm3)
M = 11,200 g

51. Do Now: D = 0.87 g/mL V = ? M = 25 g GIVEN: WORK:
A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?
GIVEN:
D = 0.87 g/mL
V = ?
M = 25 g
WORK:

52. D. Density D = 0.87 g/mL V = M V = ? M = 25 g V = 25 g 0.87 g/mL
A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?
GIVEN:
D = 0.87 g/mL
V = ?
M = 25 g
WORK:
V = M D
V = g
0.87 g/mL
V = 29 mL

53. III. Unit Conversions

54. A. SI Prefix Conversions
1. Find the difference between the exponents of the two prefixes.
2. Move the decimal that many places.
To the left
or right?

55. A. SI Prefix Conversions
Symbol
Factor
mega- M
106
kilo- k
103
BASE UNIT
---
100
deci- d
10-1
move left
move right
centi- c
10-2
milli- m
10-3
micro- μ
10-6
nano- n
10-9
pico- p
10-12

56. A. SI Prefix Conversions
1) 20 cm = ______________ m
2) L = _____________ mL
3) 45 μm = ______________ nm
4) 805 dm = ______________ km

57. A. SI Prefix Conversions
0.2
1) 20 cm = ______________ m
2) L = ______________ mL
3) 45 μm = ______________ nm
4) 805 dm = ______________ km 32
45,000
0.0805
C. Johannesson

58. DO NOW
A golden-colored cube is handed to you. The person wants you to buy it for $100, saying that is a gold nugget. You pull out your old geology text and look up gold in the mineral table, and read that its density is 19.3 g/cm3. You measure the cube and find that it is 2 cm on each side, and weighs 40 g.
What is its density?
Is it gold?
Should you buy it?

59. Conversion Factors Conversion Factors
Conversion factor – a ratio derived from the equality between two different units that can be used to convert from one unit to the other.
Example: the conversion between quarters and dollars:
4 quarters dollar
1 dollar or quarters

60. Conversion Factors Conversion Factors
Example:
Determine the number of quarters in 12 dollars?
Number of quarters = 12 dollars x conversion factor
? Quarters = 12 dollars x 4 quarters = 48 quarters
1 dollar

61. Learning Check 1. Liters and mL 2. Hours and minutes
Write conversion factors that relate each of the following pairs of units:
1. Liters and mL
2. Hours and minutes
3. Meters and kilometers

62. B. Dimensional Analysis
The “Factor-Label” Method
Units, or “labels” are canceled, or “factored” out to make your calculations easier

63. Do Now How many hours are in 2.3 years?
*use dimensional analysis to solve this problem*

64. B. Dimensional Analysis
Steps:
1. Identify starting & ending units.
2. Line up conversion factors so units cancel.
3. Multiply all top numbers & divide by each bottom number.
4. Check units & answer.

65. Learning Check a) 2440 cm b) 244 cm c) 24.4 cm
1) A rattlesnake is 2.44 m long. How long is the snake in cm?
a) cm
b) 244 cm
c) 24.4 cm
2.44 m x cm = 244 cm (b)
1 m

66. B. Dimensional Analysis
2) Your European hairdresser wants to cut your hair cm shorter. How many inches will he be cutting off?
8.0 cm
1 in
2.54 cm
= 3.2 in

67. B. Dimensional Analysis
3) A piece of wire is 1.3 m long. How many 1.5-cm pieces can be cut from this wire?
1.3 m
100 cm
1 m
1 piece
1.5 cm
= 86 pieces

68. Do Now How many meters are 372.4 inches?
*use dimensional analysis to solve this problem*

69. Quantitative vs. Qualitative Data
Quantitative data is information about quantities; that is, information that can be measured and written down with numbers. 
Ex.
Qualitative data is descriptive data that cannot be quantified.

70. Identify the following as quantitative or qualitative
1. The book is red.
2. The apple has a mass of 2.34 g.
3. The temperature of the room is 412K.
4. There are 4 blue desks in the front of the room.
6. The apple smells rotten.