PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1 DR. AUGUSTINE OFORI AGYEMAN Assistant professor of...
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Transcript of PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1 DR. AUGUSTINE OFORI AGYEMAN Assistant professor of...
PRINCIPLES OF CHEMISTRY I
CHEM 1211
CHAPTER 1 DR. AUGUSTINE OFORI AGYEMAN
Assistant professor of chemistryDepartment of natural sciences
Clayton state university
CHAPTER 1
MEASUREMENT
- Is the determination of the dimensions, capacity, quantity, or extent of something
- Is a quantitative observation and consists of two parts: a number and a scale (called a unit)
- Is the tool chemists use most
Examplesmass, volume, temperature, pressure, length, height, time
MEASUREMENT
SIGNIFICANT FIGURES
Precision - Provides information on how closely individual(repeated) measurements agree with one another
Accuracy - Refers to how closely individual measurements
agree with the true value (correct value)
Precise measurements may NOT be accurate
SIGNIFICANT FIGURES
Exact Numbers - Values with no uncertainties
- There are no uncertainties when counting objects or people(24 students, 4 chairs, 10 pencils)
- There are no uncertainties in simple fractions(1/4, 1/7, 4/7, 4/5)
Inexact Numbers - Associated with uncertainties
- Measurement has uncertainties (errors) associated with it- It is impossible to make exact measurements
SIGNIFICANT FIGURES
Measurements contain 2 types of information- Magnitude of the measurement- Uncertainty of the measurement
Only one uncertain or estimated digit should be reported
Significant Figures digits known with certainty + one uncertain digit
RULES FOR SIGNIFICANT FIGURES
1. Nonzero integers are always significant 4732 (4 sig. figs.) 875 (3 sig. figs.)
2. Leading zeros are not significant 0.0045 (2 sig. figs.) 0.00007895 (4 sig. figs.) The zeros simply indicate the position of the decimal point
3. Captive zeros (between nonzero digits) are always significant 1.0025 (5 sig figs.) 12000587 (8 sig figs)
RULES FOR SIGNIFICANT FIGURES
4. Trailing zeros (at the right end of a number) are significant only if the number contains a decimal point 2.3400 (5 sig figs) 23400 (3 sig figs)
5. Exact numbers (not obtained from measurements) are assumed to have infinite number of significant figures
RULES FOR SIGNIFICANT FIGURES
How many significant figures are present in each of the following?What is the uncertainty in each case?
significant figures uncertainty1.24 g 3 ± 0.01 g
0.0024 L 2 ± 0.0001 L0.39200 mL 5 ± 0.00001 mL3.0026 kg 5 ± 0.0001 kg
RULES FOR SIGNIFICANT FIGURES
Rounding off Numbers
1. In a series of calculations, carry the extra digits through to the final result before rounding off to the required significant figures
2. If the first digit to be removed is less than 5, the preceding digit remains the same (round down) Round to two significant figures 2.53 rounds to 2.5 and 1.24 rounds to 1.2
RULES FOR SIGNIFICANT FIGURES
Rounding off Numbers
3. If the first digit to be removed is greater than 5, the preceding digit increases by 1 (round up) (2.56 rounds to 2.6 and 1.27 rounds to 1.3)
4. If the digit to be removed is exactly 5 (round even)- The preceding number is increased by 1 if that results in an even number (2.55 rounds to 2.6 and 1.35000 rounds to 1.4)- The preceding number remains the same if that results in an odd number (2.45 rounds to 2.4 and 1.25000 rounds to 1.2)
RULES FOR SIGNIFICANT FIGURES
Multiplication and Division- The result contains the same number of significant figures as the
measurement with the least number of significant figures
2.0456 x 4.02 = 8.223312 = 8.22
3.20014 ÷ 1.2 = 2.6667833 = 2.7
- The certainty of the calculated quantity is limited by the least certain measurement, which determines the final number of
significant figures
RULES FOR SIGNIFICANT FIGURES
Addition and Subtraction- The result contains the same number of decimal places as the
measurement with the least number of decimal places
- The certainty of the calculated quantity is limited by the least certain measurement, which determines the final number of
significant figures
5.479
0.234
3.2
2.045
4.028
3.52
7.548
= 5.5 = 4.03 6.00
3.47
47.9
= 6.00 (not 6)
SCIENTIFIC NOTATION
- Used to express too large or too small numbers (with many zeros)in compact form
- The product of a decimal number between 1 and 10 (the coefficient)and 10 raised to a power (exponential term)
24,000,000,000,000 = 2.4 x 1013
coefficientexponential term
exponent (power)
0.000000458 = 4.58 x 10-7
SCIENTIFIC NOTATION
- Provides a convenient way of writing the required number of significant figures
6300000 to 4 significant figures = 6.300 x 106
2400 to 3 significant figures = 2.40 x 103
0.0003 to 2 significant figures = 3.0 x 10-4
SCIENTIFIC NOTATION
- Add exponents when multiplying exponential terms(5.4 x 104) x (1.23 x 102)
= (5.4 x 1.23) x 10 4+2
= 6.6 x 106
- Subtract exponents when dividing exponential terms(5.4 x 104)/(1.23 x 102)
= (5.4/1.23) x 10 4-2
= 4.4 x 102
MEASUREMENT SYSTEMS
Two measurement systems:
English System of Units (commercial measurements): pound, quart, inch, foot, gallon
Metric System of Units (scientific measurements)SI units (Systeme International d’Unites)
liter, meter, gramMore convenient to use
FUNDAMENTAL (BASE) UNITS
Physical Quantity
MassLengthTimeTemperatureAmount of substanceElectric currentLuminous intensity
Name of Unit
KilogramMeterSecondKelvinMoleAmpereCandela
Abbreviation
kgms (sec)KmolAcd
Area = length x length = m x m = m2
Volume = m x m x m = m3
Volume may also be expressed in LITERS (L)1L = 1000 mL = 1000 cm3 or cubic centimeters
(c.c.)Implies 1mL = 1c.c.
mL is usually used for volumes of liquids and gasesc.c. is usually used for volumes of solids
Density = kg/ m3
DERIVED UNITS
DERIVED UNITS
Physical Quantity
Force PressureEnergyPowerFrequency
Name of Unit
NewtonPascalJouleWattHertz
Abbreviation
N (m-kg/s2)Pa (N/m2; kg/(m-s2)J (N-m; m2-kg/s2)W (J/s; m2-kg/s3)Hz (1/s)
Prefix
GigaMegaKiloDeciCentiMilli
MicroNanoPico
Femto
Abbreviation
GMkdcmµnpf
Notation
109
106
103
10-1
10-2
10-3
10-6
10-9
10-12
10-15
UNIT CONVERSIONS
UNIT CONVERSIONS
1 gigameter (Gm)
1 megameter (Mm)
1 kilometer (km)
1 decimeter (dm)
1 centimeter (cm)
1 millimeter (mm)
1 micrometer (µm)
1 nanometer (nm)
1 picometer (pm)
1 femtometer (fm)
= 109 meters
= 106 meters
= 103 meters
= 10-1 meter
= 10-2 meter
= 10-3 meter
= 10-6 meter
= 10-9 meter
= 10-12 meter
= 10-15 meter
UNIT CONVERSIONS
Length/Distance
2.54 cm = 1.00 in.12 in. = 1 ft1 yd = 3 ft1 m = 39.4 in.1 m = 1.09 yd1 km = 0.621 mile1 km = 1000 m
Time
1 min = 60 sec1 hour = 60 min24 hours = 1 day7 days = 1 week
Volume
1 gal = 4 qt1 qt = 0.946 L1 L = 1.06 qt1 L = 0.265 gal1 mL = 0.034 fl. oz.
Mass
1 Ib = 454 g1 Ib = 16 oz1 kg = 2.20 lb1 oz = 28.3 g
UNIT CONVERSIONS
1 km = 1000 m orm1000
km 1
km 1
m 1000»
Conversion Factors
1 L = 1000 mL
24 hours = 1 day
1 kg = 2.20 lb
»
»
»
mL 1000
L 1
day1
hours24
lb 2.20
kg 1
or
or
or
L 1
mL 1000
hours24
day1
kg 1
lb 2.20
UNIT CONVERSIONS
given number · unit new unit
unit to be converted= new number · new unit
quantity to beexpressed in
new unitsconversion factor
quantity nowexpressed in
new units
given data desired unit
unit of given data= answer in desired unit
Convert 34.5 mg to g
How many gallons of juice are there in 20.0 liters of the juice?
gallon5.30liter1
gallon0.265xliters20.0
g10x3.45org0.0345mg1000
g1xmg34.5 2
UNIT CONVERSIONS
Convert 4.0 gallons to quarts
quarts16quarts15.9559liter0.946
quart1x
gallons0.265
liter1xgallons4.0
Convert 2.64 μg to kg
Convert 3.912 m2 to km2
2623
22 km10x3.912
m)(10
km) (1xm3.912
kg10x2.64g10
kg1x
μg1
g10xμg2.64 9
3
-6
UNIT CONVERSIONS
Convert 4.0 cm3 to μm3
μm10x4.0cm)(10
μm)(1xcm4.0 12
34-
33
DENSITY
- The amount of mass in a unit volume of a substance
Ratio of mass to volume =Density =
UnitsSolids: grams per cubic centimeter (g/cm3)
Liquids: grams per milliliter (g/mL)Gases: grams per liter (g/L)
- Density of 2.3 g/mL implies 2.3 grams per 1 mL
- Density usually changes with change in temperature
volume
mass
For a given liquid:
- Objects with density less than that of the liquid will float
- Objects with density greater than that of the liquid will sink
- Objects with density equal to that of the liquid will remainstationary (neither float nor sink)
DENSITY
The liquid level in a graduated cylinder reads 12.20 mL.The level rises to 18.90 mL when 129.31 g of piece of
gold is added to the cylinder. What is the density of gold?
Volume of the piece of gold = 18.90 mL – 12.20 mL = 6.70 mLMass of the piece of gold = 129.31 g
Density = mass/volume = 129.31 g/6.70 mL = 19.3 g/mL or 19.3 g/cm3
DENSITY
TEMPERATURE
- The degree of hotness or coldness of a body or environment
3 common temperature scales Metric system: Celsius and Kelvin
English system: Fahrenheit
Celsius Scale (oC): Reference points are the boiling and freezing points of water (0oC and 100oC) - 100 degree interval
Kelvin Scale (K): Is the SI unit of temperature (no degree sign)
The lowest attainable temperature on the Kelvin scale is 0 (-273 oC) referred to as the absolute zero
TEMPERATURE
Fahrenheit Scale: Water freezes at 32oF and boils at 212oF- 180 degree interval
or
10o, 40o, 60o may be considered as 2 significant figures
100o may be considered as 3 significant figures
32F9
5C oo 32C
5
9F oo
273KCo 273CK o or
TEMPERATURE
C21.73)(9
53229
9
5C oo
F8484.23252.232295
9F oo
C 244- 27329C oo
K 302 27392K Convert 29 oC to K
Convert 29 K to oC
Convert 29 oF to oC
Convert 29 oC to oF