1. BASIC CHEMISTRY CHM 138 CHAPTER 1: UNITS OF MEASUREMENTS

2. Chemistry is the study of matter and the changes it undergoes
Matter is anything that occupies space and has mass.
A substance is a form of matter that has a definite composition and distinct properties.
liquid nitrogen
gold ingots
silicon crystals

3. DIMENSIONS Defined as:
Any physical quantities that can be measured by measuring devices.
There are 2 types of dimension:
1.Basic dimension
The simplest and the most basic physical quantities
There are 7 basic dimensions:
- Length (L)
- mass (m)
- time (t)
- temperature (T)
- amount of substances (n)
- luminous intensity (I)
- electrical current

4. Combination of Basic dimensions
2. Derived dimensions
The compound physical quantities that are obtained by combining basic physical by multiplying / dividing the basic dimensions.
Derived dimensions
Combination of Basic dimensions
Area
Length x length
Volume
Length x length x length
Speed
Length / time
Force
(mass x length) / (time x time)
Density
Mass / (length x length x length)
Pressure
Mass / (time x time)

5. International System of Units (SI)

6. Meter per second squared m.s-2 Pressure Newton per meter squared,
S.I system of units
Dimension
Symbol of dimension
Name of unit
Symbol of unit
Definition of unit
Basic SI Units
length L
meter m
mass
kilogram Kg
time t
second s
temperature T
Kelvin, degree celcius
K, °C
Amount of substance n
mole
mol
Derived SI Units
Energy E
Joule
J / Nm
Kg.m2.s-2
Force F
Newton N
Kg.m.s-2
Power P
watt
W /J/s
Kg.m2.s-3
Velocity V
Meter per second
m.s-1
Acceleration a
Meter per second squared
m.s-2
Pressure
Newton per meter squared,
Pascal
N.m-2 Pa
Density ƿ
Kilogram per cubic meter
Kg.m-3

7. American Engineering system of units Dimension Symbol of dimension
Name of unit
Symbol of unit
Definition of unit
Basic SI Units
length L
Feet ft
mass m
Pound mass
Ibm
force F
Pound force
Ibf
time t
Second S
temperature T
Degree Rankie,
Degree Fahrenheit °R °F
Amount of substance n
mole
Ib mol
Derived SI Units
Energy E
Foot pound force
Ft.Ibf
Force
Power P
Horsepower hp
Velocity V
feet per second
ft.s-1
Acceleration a
feet per second squared
ft.s-2
Pressure
Pound force per second inch
Psi
Density ƿ
Pound mass per cubic foot
Ibm.ft-3

8. Quantity Equivalent Values
Mass
1 kg = 1000 g = metric ton = Ibm = oz
1 Ibm = 16 oz = 5 x 10-4 ton = g = kg
Length
1 m = 100 cm = 1000 mm = 106 microns (µm) = 1010 angstroms (A)
= in. = ft = yd = mile
1 ft = 12 in. = 1/3 yd = m = cm
Volume
1 m3 = 1000 L = 106 cm3 = 106 mL
= ft3 = imperial gallons = gal
= qt
1 ft3 = 1728 in.3 = gal = m3 = L
= 28,317 cm3
Force
1 N = 1 kg.m/s2 = 105 dynes = 105 g.cm/s2 = Ibf
1 Ibf = Ibm.ft/s2 = N = x 105 dynes
Pressure
1 atm = x 105 N/m2 (Pa) = kPa = bar
= x 106 dynes/cm2
= 760 mm Hg
= Ibf/in.2 (psi) = 33.9 ft
= in. Hg
Energy
1 J = 1 N.m = 107 ergs = 107 dyne.cm
= x 10-7 kW.h = cal
= ft-Ibf = x 10-4 Btu
power
1 W = 1 J/s = cal/s = ft.Ibf/s = x 10-4 Btu/s
= x 10-3 hp

9. 1 year = 365 days
1 day = 24 hours
1 hour = 60 minutes
1 minute = 60 seconds
30 days = 1 month
1 year = 12 month
1 qt = L
1 gal = L
1 L = fl oz
1 fl oz = ml
1 L = qt
1 in = 2.54 cm
1 m = in
1 mile = km
1 mile = 5280 feet
1 mile = 1760 yards
3 feet = 1 yard
12 inches = 1 feet
1 oz = g
1 lb = g
1 kg = lb
1 g = grains

11. MASS AND WEIGHT Matter - anything that occupies space and has mass.
mass – measure of the quantity of matter
SI unit of mass is the kilogram (kg)
1 kg = 1000 g = 1 x 103 g
weight – force that gravity exerts on an object
weight = c x mass
A 1 kg bar will weigh
1 kg on earth
0.1 kg on moon
on earth, c = 1.0
on moon, c ~ 0.1

12. VOLUME Volume – SI derived unit for volume is cubic meter (m3)
1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3
1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3

13. Density – SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
d = m V
density =
mass
volume
EXAMPLE:
A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass?
d = m V
m = d x V
= 21.5 g/cm3 x 4.49 cm3 = 96.5 g

14. Ex. 1.1

15. Ex. 1.2

17. A Comparison of Temperature Scales
Three temperature scales:
0F – degrees Fahrenheit
0C – degrees Celcius
K - Kelvin
K = oC
9 oF
oF = x oC oF
5 oC
5 oC
oC = (oF – 32oF) x
9 oF

18. Example:
Convert F to degrees Celsius.
0C = x (0F – 32) 9 5
0C = x (172.9 – 32) = 78.3 9 5

20. Scientific Notation The number of atoms in 12 g of carbon:
602,200,000,000,000,000,000,000
6.022 x 1023
The mass of a single carbon atom in grams:
1.99 x 10-23
N x 10n
N is a number
between 1 and 10
n is a positive or
negative integer

21.
move decimal left
move decimal right
n > 0
n < 0
= x 102
= 7.72 x 10-6
Addition or Subtraction
Write each quantity with the same exponent n
Combine N1 and N2
The exponent, n, remains the same
4.31 x x 103 =
4.31 x x 104
= 4.70 x 104

22. (a x 10m) x (b x 10n) = (axb) x 10m+n
Multiplication
Multiply N1 and N2
Add exponents n1 and n2
(4.0 x 10-5) x (7.0 x 103) = ?
= (4.0 x 7.0) x (10-5+3)
= 28 x 10-2
= 2.8 x 10-1
(a x 10m) x (b x 10n) = (axb) x 10m+n
Division
Divide N1 and N2
Subtract exponents n1 and n2
8.5 x 104 ÷ 5.0 x 109 = ?
= (8.5 ÷ 5.0) x 104-9
= 1.7 x 10-5
(a x 10m) ÷ (b x 10n) = (a ÷ b) x 10m-n

23. Significant Figures
- The meaningful digits in a measured or calculated quantity.
RULES:
Any digit that is not zero is significant
1.234 kg significant figures
Zeros between nonzero digits are significant
606 m significant figures
Zeros to the left of the first nonzero digit are not significant
0.08 L significant figure
If a number is greater than 1, then all zeros to the right of the decimal point are significant
2.0 mg significant figures

24. If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant
g 3 significant figures
Numbers that do not contain decimal points, zeros after the last nonzero digit may or may not be significant.
400 cm or 2 or 3 significant figures
4 x significant figures
4.0 x significant figures

25. How many significant figures are in each of the following measurements?
24 mL
2 significant figures
3001 g
4 significant figures m3
3 significant figures
6.4 x 104 molecules
2 significant figures
560 kg
2 significant figures

26. Significant Figures Addition or Subtraction
The answer cannot have more digits to the right of the decimal
point than any of the original numbers.
89.332
1.1 +
90.432
one significant figure after decimal point
round off to 90.4
3.70
0.7867
two significant figures after decimal point
round off to 0.79

27. Significant Figures Multiplication or Division
The number of significant figures in the result is set by the original number that has the smallest number of significant figures
4.51 x =
= 16.5
3 sig figs
round to
3 sig figs
6.8 ÷ =
= 0.061
2 sig figs
round to
2 sig figs

28. Significant Figures Exact Numbers
Numbers from definitions or numbers of objects are considered
to have an infinite number of significant figures
The average of three measured lengths; 6.64, 6.68 and 6.70? 3
= = 6.67
= 7
Because 3 is an exact number

31. Dimensional Analysis Method of Solving Problems
Determine which unit conversion factor(s) are needed
Carry units through calculation
If all units cancel except for the desired unit(s), then the problem was solved correctly.
given quantity x conversion factor = desired quantity
desired unit
given unit
given unit x
= desired unit

32. Dimensional Analysis Method of Solving Problems
How many mL are in 1.63 L?
Conversion Unit 1 L = 1000 mL 1L
1000 mL
1.63 L x
= 1630 mL

33. The speed of sound in air is about 343 m/s
The speed of sound in air is about 343 m/s. What is this speed in miles per hour?
conversion units
meters to miles
seconds to hours
1 mi = 1609 m
1 min = 60 s
1 hour = 60 min
343 m s x
1 mi
1609 m
60 s
1 min x
60 min
1 hour x
= 767 mi
hour