1. Chem 20-1204 El Camino College
Ch. 1: Measurements
Chem
El Camino College

2. Ex. Which is larger, an in. or a meter?
Units
Units of Length
meter (m), centimeter (cm), inch (in.)
1 m = 100 cm
1 m = 39.4 in.
2.54 cm = 1 in.
Ex. Which is larger, a meter or a cm?
a meter
Ex. Which is larger, an in. or a meter?
a meter.

3. Ex. Which is larger, a quart or a liter?
Units
Units of Volume
liter (L), milliliter (mL), quart (qt)
1 L = 1000 mL
1 L = 1.06 qt
946 mL = 1 qt
Ex. Which is larger, a milliliter or a liter?
a liter
Ex. Which is larger, a quart or a liter?
a liter.

5. Units Units of Mass Ex. Which is larger, a g or a kg? a kg
gram (g), kilogram (kg), pound (lb)
1 kg = 1000 g
1 kg = 2.20 lb
454 g = 1 lb
Ex. Which is larger, a g or a kg?
a kg
Ex. Do you weigh a higher number of
pounds or kilograms?
lbs

7. Units Units of Temperature
Fahrenheit (oF), Celsius (oC), Kelvin (K)
freezing pt of H2O is 32 oF, 0 oC, 273 K
boiling pt of H2O is 212 oF, 100 oC, 373 K
Ex. What is being measured: length, volume, mass, or temp?
292 K
23 mL
0.004 cm.
temp
volume
length

11. For Very Large or Small Numbers
Scientific notation has a specific form
a.bcd x 10e
a.bc (the number must be ³1 to <10)
10e (the e is the exponent)
x 101 = x 10
x 102 = x 100
x 103 = x1000
x 10-1 = x .1
x 10-2 = x .01
x 10-3 = x .001

12. Solved Examples Write 53 in scientific notation
Convert to a.bc form (between 1 and 10)
5.3
To go from the a.bc form to 53, the decimal moves 1 place to the right
5.3 x 101

13. Solved Examples Write 8769 in scientific notation
Convert to a.bc form (between 1 and 10)
8.769
To go from the a.bc form to 8769, the decimal moves 3 places to the right
8.769 x 103

14. Solved Examples Write 100.30 in scientific notation
Convert to a.bc form (between 1 and 10)
1.0030
To go from the a.bc form to , the decimal moves 2 places to the right
x 102

15. Solved Examples Write 0.00367 in scientific notation
Convert to a.bc form (between 1 and 10)
3.67
To go from the a.bc form to , the decimal moves 3 places to the left
3.67 x 10-3

16. Examples Write these in scientific notation 501 = 3,256,000 =
0.042 = =
5.01 x 102
3.256 x 106
4.2 x 10-2
5.395 x 10-4

17. Solved Examples Write 1.0389 x 102 in decimal form
x 102 means that the decimal moves 2 places to the right
103.89
Write 8.0 x 10-3 in decimal form
8.0 x 10-3 means that the decimal moves 3 places to the left
.0080

18. Examples Write these in decimal notation 3 x 100 = 6.022 x 104 = 3
60220
99.9

19. On Your Calculator Don’t use the 10x key Don’t press “x 10”
You must use the EE or EXP key
5.62 x 10-3 is 5.62 exp 3 +/-
Try this calculation. If you get a different result, see me after class
5.62 x 10-3
8.84 x 104
= x 10-8

23. Place Names ___ ___ ___ . ___ ___ ___ hundreds tens ones tenths
thousandths
hundredths

24. Dimensional Analysis How many minutes are in 2.0 hrs?
The 2.0 hrs is your given information
The conversion (60 min/1 hr) is called a conversion factor
Always start with the given information
Write the conversion factor so the units to be cancelled are on the bottom.
2.0 hrs
60 min
1 hr
= 120 min

25. Dimensional Analysis How many minutes in 936.2 sec? 936.2 sec 1 min
How many hrs in 53 min?
53 min
1 hr
60 min
= 0.88 hr

26. Dimensional Analysis
If you need two conversions, don’t stop in the middle. Write one conversion after the other.
Hit the times (X) key between numerators
Hit the divide (/) key between denominators
How many hours in 9365 sec?
9365 sec
1 min
60 sec
1 hour
60 min
= hr

27. Dimensional Analysis How many hrs in 5,877 sec? 5,877 sec 1 min 1 hour
How many minutes in days?
0.052 days
24 hrs
1 day
60 min
1 hr
= 75 min

28. Metric Prefixes to Memorize
prefix symbol multiple
kilo k g / 1 kg
centi c 1 m / 100 cm
milli m 1 L / 1000 mL
micro m 1 g / 1 x 106 mg
nano n 1 m / 1 x 109 nm
also useful is 1 cm = 10 mm

29. Metric Conversion Factors
There are many ways to write conversion factors
Make sure you know which unit is bigger
Many small units = one big unit
A fraction of a big unit = one small unit
1 m
100 cm
100 cm
1 m
1 x 102 cm
1 m
1 cm
.01 m

30. Examples: Use Dimensional Analysis
Always put the number by itself before the conversion factor
How many cm in 4.6 m?
4.6 m
100 cm
1 m
= 460 cm
How many kg in 54.8 g?
1 kg
1000 g
54.8 g
= kg

31. Examples How many kL in 4,329,647 L? 1 kL 1000 L = 4329.647 kL
How many mm in 0.33 m?
0.33 m
1 x 106 mm
1 m
= 3.3 x 105 mm
How many kg in 828 mg?
828 mg
1 g
1000 mg
1 kg
1000 g
= 8.28 x 10-4 kg

32. English Units These are the most common US units mass: ounce, pound
length: inch, foot, yard
volume: cubic inch, fl. oz., gallon

33. Metric-US Conversions: Don’t Memorize
1.06 qt = 1 L
1 qt = 946 mL
1 lb = 454 g
1 oz = 28.3 g
2.20 lb = 1 kg
1 in. º 2.54 cm
39.4 in. = 1 m
0.621 mi = 1 km

34. Examples How many liters are in 2.98 quarts? 2.98 qt 1 L 1.06 qt =
How many ounces are in g?
500.0 g
1 oz
28.3 g =
17.7 oz
How many cm in in.?
8.994 in.
2.54 cm
1 in. =
22.84 cm

35. Place Names ___ ___ ___ . ___ ___ ___ hundreds tens ones tenths
thousandths
hundredths

36. Significant Figures Sig figs apply to measured amounts
Sig figs don’t apply to counted things

37. Significant Figures
For any apparatus, read 1 place past the smallest mark
The last significant digit is estimated (the doubtful digit).

38. Significant Figures 28 oC The smallest mark is in the tens place
One place past the smallest mark is the ones.

39. Ex. Read These
3.6 oC
110 oC
4.7 oC
5.5 oC
meas-4

40. Right on the Line? Always read to one place past the smallest mark
Always read a piece of equipment to the same place.
Note: Read the meniscus (the bottom of the belly for water)

41. Right on the Line?
3.0 mL

42. Conversion Factors in Problems
Read the problem carefully, then write a conversion factor
When solving, write a number by itself first, then write the conversion factor

43. The conversion factor is
Example
A car is traveling 65.9 miles per hour. How many miles will it go in 13.3 hrs?
65.9 miles
1 hour
65.9 miles
1 hour
The conversion factor is or
13.3 hrs
65.9 miles
1 hour =
876 miles

44. A car is traveling 38. 8 miles per hour
A car is traveling 38.8 miles per hour. How many hrs will it take to go 51.0 miles?
51.0 mi
1 hr
38.8 mi =
1.31 hr
A pool empties at 4.2 gal per sec. How many min will it take to empty 3200 gal?
3200 gal
1 sec
4.2 gal
1 min
60 sec =
13 min

45. Density m v Density is mass/volume D =
Find the density of 3.8 mL of liquid that has a mass of 5.8 g.
5.8 g
3.8 mL =
1.5 g/mL
Note: 1 mL º 1 cm3 º 1 cc

47. Figure 1.11

48. The density of gold is 19.3 g/cm3. Find the mass of 87.3 cm3 of gold.
Find the volume of 0.53 g of gold using the density of 19.3 g/cm3.
0.53 g
1 cm3
19.3 g
= cm3

50. Density and Solids
The mass of a solid is measured on a balance or scale
The volume of a solid may be measured by volume displacement
Measure the vol of water in a cylinder
Add the solid
Measure the vol of water again
Vfinal - Vinitial = Vsolid

51. A cylinder contains 11. 3 mL water
A cylinder contains 11.3 mL water. A piece of aluminum is added, and the water level rises to 16.0 mL. What is the volume of the aluminum?
16.0 mL mL = 4.7 mL
If the Al has a mass of 12.7 g, what is the density of the Al?
12.7 g
4.7 mL =
2.7 g/mL

52. Example
A cylinder contains 35.5 mL water. A piece of zinc is added, and the water level rises to 45.0 mL. If the mass of the zinc is g, what is the density of the zinc?
Volume 45.0 mL mL = 9.5 mL
Density
68.60 g
9.5 mL =
7.2 g/mL