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

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

3. Example: Cookie Monster is Blue
Making Measurements
Ch 2.2
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

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

5. 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.

7. International System of Units

8. SI Units (Systeme Internationale)
Quantity
Unit
Symbol
tool
Length
Meter m
Ruler, meter stick
Mass
Gram g
Scale/ balance
Not the same as weight
Temperature
Kelvin/ Celsius
K / C
Thermometer
K=C+273
Time
Seconds s
Stopwatch
Volume
Liter or cm3
L or cm3
Graduated cylinder
1mL=1cm3
Density
Mass/Vol
g/mL
Scale & cylinder
Derived unit
Energy
Joule J
coulometer
Can also use calorie
Amount
Mole
Mol

9. SI Units (Systeme Internationale)
Meter (m) for length Use 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 thermometer to measure
oC is another option, but not Fahrenheit (in the metric system)
Second (s) for time
Use a stopwatch to 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
Mass: amount of matter - Gravity does not affect mass
Weight: measure of gravitational pull

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 mL=cm3
Speed: meters/ second

12. milli- (1/1000x), centi-(1/100x),
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)

13. 100 cm = 1 m Prefixes you need to memorize…
Metric Prefixes
Prefixes you need to memorize…
milli- (1/1000), centi-(1/100), kilo-(1000x)
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.
100 cm = 1 m

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

15. Conversion factors: a ratio of equal proportions, expressed as a fraction
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.

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

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

18. 3. 600 g = __________ kg 4. 8900 mm = __________ m
More examples
g = __________ kg
mm = __________ m
s = ___________ms
kg = __________ mg
cm3 = __________ m3
m3 = ________ mm3
Answers
3) 0.6kg
4) 8.9m
5) 2300ms
6) 250,000mg
7) m3 8)

19. Date SI Unit Practice Convert each of the following:
kg = __________ g
cm = __________ m
ml = __________ l
4. 25 mg = __________g
cm = __________ mm
ml = __________ l
g = __________ kg
mm = __________ m
m = __________ mm
kg = __________ mg
1000g
1 kg
Example: 3.68kg * = g
3.68kg * 103
Use table 2 on pg35!
However you won’t get the table for your quiz

20. What SI unit would you use to measure….
Date: SI Unit Practice
What SI unit would you use to measure….
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?
The length of a football field?
The WIDTH of a strand of hair?
The mass of an elephant?
The mass of an ant?

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

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

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

24. 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

25. 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- - y1 g
X2 – x1 mL
rise
run
Ex: 11-3 g
11-3mL
= 1 g/mL

26. 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

28. 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
50mL
60ml
60-50=10mL
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.

29. How would temp affect density??
Ex: 3. The density of silver is 10.0 g/cm3. If you have a sample size of 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?

30. 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

31. The density of silver is 10. 0 g/cm3. If you have a sample size of 17
The density of silver is g/cm3. If you have a sample size of 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?

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

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

34. Value experimental – Value accepted Value accepted
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 g/mL. What is her percent error?
Example:

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

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

37. Rules for Significant Figures: All nonzero numbers are significant
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)
Examples:
245 G 3 sf
40.7 L
87009 km m
0.09 kg
85.00g
2000 m
2000. m 3 5 3 1 4 6 1 4

38. a) 12,389 = _____ b) 0.452 = _____ c) 10.26 = _____ d) 23.000 = _____
When given a number, you must be able to determine the number of sig.figs. in it.
a) 12,389 = _____
All non-zero #’s are significant
b) = _____
Zeros before a decimal are not imp unless it is part of a whole number
c) = _____
zeros in between #’s are significant
d) = _____
Zeros after a decimal are significant IF THERE IS A WHOLE #
e) 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) = _____
zeros after a decimal but with no whole # are NEVER significant.
Again, use sci.not.

39. 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

40. 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 g = Multiplication and Division with Sig Figs: answer must use same # 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

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

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

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

44. B. Solve the following problems and report answers with appropriate number of significant digits.
1)      cm cm + 0.68 cm +12.0 cm = 
2)     1.6 km m cm =  
3)     g g =   
4)     m - 6.0 m =  
5)     m kg=  
6)     1.31 cm x 2.3 cm =  
7)     m x 6.201 m = 
8)    20.2 cm / 7.41 s =  
9)    g / g =

45. B practice
1)      cm cm + 0.68 cm +12.0 cm =  26.3 cm
2)     1.6 km m cm =   1.2 x 103 or 1203 m
3)     g g =    0.5 g
4)     m - 6.0 m =  4.4 m
5)     m kg=   can’t add m and kg
6)     1.31 cm x 2.3 cm =   3.0 cm2
7)     m x 6.201 m =  m2
8)    20.2 cm : 7.41 s =   2.73 cm/s
9)    g : g = g

46. 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?

47. Name the tool and units to measure each:
Length
Volume
Mass
Temperature
Density

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!

51. Practice:

52. 3. Mass
The quantity of matter
Tool?
balance, scale, etc.
Units?
Kilograms (kg)
Grams (g)
We use digital scales (usually)…so just record what the scale says

53. Mass continued…
Scale must read zero before you place anything on it! If you want to measure the mass of something inside a container…you must measure the empty container first.
How much mass does the water have?
462.3 g
450.0 g

54. 4. Temperature
The amount of heat present
Tool?
thermometer
Units?
Degrees Celsius (°C)

55. 5. Density?
The amount of matter in a space
Units?
g/cm3 or g/mL
Tool?
scale and
ruler or graduated cylinder