Chem 101-01 Chemistry The Central Science
Chem 101-01 Chemistry The Central Science
Chem 101-01 Chemistry The Central Science
Dr. A. Al-Saadi
Chapter 1
Section 1
Why Chemistry?
Everything in this universe is made out of approximately 100 different kinds of atoms. atoms
Sand (Silicon, Oxygen) Table Salt (Sodium, Chloride) Water (Oxygen, Hydrogen)
Dr. A. Al-Saadi
08-Sep-11
Chapter 1
Section 1
Why Chemistry?
Dr. A. Al-Saadi
Chapter 1
Section 1
Why Chemistry? Chemical reactions are very common in this life d thi lif and are important for our survival i t tf i l on the Earth. They also cause many problems for humanity! Can you think of good and bad good bad chemical reactions?
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08-Sep-11
Chapter 1
Section 1
Scientific Method
The scientific method is the way used by scientists to understand the universe y and its changes. The more creative youre at solving problems, the more effective you will be in your career and your personal life. C e s y e ps o develop so v g Chemistry helps to deve op solving problems capabilities.
Dr. A. Al-Saadi
Chapter 1
Section 1
Scientific Method
Dr. A. Al-Saadi
08-Sep-11
Chapter 1
Section 1
Scientific Method
A set of valid hypotheses is alid h potheses assembled into a theory (model). This theory is confirmed, modified or may be discarded as more observations are recorded. Thus, it is a continuous process process.
Dr. A. Al-Saadi
Chapter 1
Section 1
Theory changes over time as more observations from experiments are recorded. p Some observations are found to apply to many different systems. Law (what happens) A summary of observed behaviors applied to different systems. L Law of conservation of mass. f ti f Law of conservation of energy. Theory (why it happens) An attempt to explain these observations.
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Dr. A. Al-Saadi
08-Sep-11
Chapter 1
Section 1
Scientific Method
Dr. A. Al-Saadi
Chapter 1
Section 2
Classification of Matter Matter is anything occupying the space and having a mass. mass Matter can be: A substance is a form of matter that has a defined composition and unique properties. A mixture is a combination of two or more substances that retain their distinct identities.
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Chapter 1
Section 2
Classification of Matter
States of matter:
Dr. A. Al-Saadi
Solid: rigid, has fixed volume and shape. Liquid: has definite volume but not fixed shape. Gas: has no fixed volume or shape. and is compressible.
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Chapter 1
Section 2
Classification of Matter
Gasoline Juices and tea Air (N2, O2, H2, CO2, etc.)
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Chapter 1
Section 2
Based on the physical properties of the substances (boiling point adsorption solubility etc ) point, adsorption, solubility, etc.) Separation methods discussed in the text:
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Chapter 1
Section 2
Chemical changes
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Chapter 1
Section 2
Classification of Matter
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Chapter 1
Section 4
Quantitative: expressed using numbers. Qualitative: expressed using properties properties. Physical properties: can be observed and measured without changing the substance.
Physical changes: the identity of the substance stays the same and only its state changes.
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Chapter 1
Section 4
Chemical properties: must be determined by the chemical changes that are observed. observed
Chemical changes: after a chemical change, the original substance no longer exists g g
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Chapter 1
Section 4
100.0 g 0.100 L 25 C
10.0 g 0.010 L 25 C
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Chapter 1
Section 3
Scientific Measurement
Making observations can be done quantitatively or qualitatively. A quantitative observation is called a measurement. It must include two important pieces of information: Number
(1) Metric Units International System (SI Units) Used in Science
Unit
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Chapter 1
Section 3
All other units of measurement can be derived from the above seven fundamental SI units .
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Chapter 1
Section 3
Units of Measurement
Number 10 1 5 20 1 60
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There are two major systems of measurements: t (1) Metric Units International System (SI Units) Used in Science S i
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Chapter 1
Section 3
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Chapter 1
Section 3
Dr. A. Al-Saadi
Must be memorized!
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Chapter 1
Section 3
Scientific Notation
0.0001 kg
110-4 kg 0.1 g
Scientific Notation
1 with 35 zeros kg
11035 kg
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Chapter 1
Section 3
Scientific Notations
123.1 = 1.231 102 = 1.231 100 0.00013 = 1.3 10-4 = 1.3 / 10000 = 0.13 10-3 Avogadros Number*: 602,214,000,000,000,000,000,000
number of atoms contained in 12 g of carbon and is equal to 1 mole.
*The
6.022 1023
Scientific notation is a very convenient way to express the number of atoms in chemistry problems.
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Chapter 1
Section 3
Temperature
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Chapter 1
Section 3
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Chapter 1
Section 3
Temperature scales for C and K are C identical, but their zeros are different.
TK = TC + 273.15 TC = TK 273.15
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Chapter 1
Section 3
Since: 180F = 100C => 9F = 5C and: 32F = 0C Then to convert from F to C: [Tf (F) 32 (F)] 5C 9F = Tc (C)
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Chapter 1
Section 3
Volume
Volume is not an SI unit, but it is extremely important in chemical y p measurements. Volume = 1m 1m 1m = 1m3
1m = 10dm (1m)3 = (10dm)3 1m3 = 1000dm3 1dm 1d 3 = 1L 1L = 1000mL = 1000cm3 1mL = 1cm3 (milli)Liter milli = 10-3 (centi)Meter centi = 10-2
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Dr. A. Al-Saadi
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Chapter 1
Section 3
Measurement of Volume
Chapter 1
Section 3
Density
Density
mass volume l
Substance
Oxygen Hydrogen Ethanol Water Aluminum Iron Mercury
Dr. A. Al-Saadi
Density (g/cm3)
0.00133 0.000084 0.789 0 789 0.998 1.47 7.87 13.6
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Chapter 1
Section 5
Uncertainty in Measurement
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Chapter 1
Section 5
Uncertainty in Measurement
Now you should be able to tell how many digits you need to include in your reading (measurement).
20 ml 20.1 ml 20.16 ml 20.160 ml 20.1600 ml Which one??
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Chapter 1
Section 5
Uncertainty in Measurement
2.5 0.1 cm
Uncertainty
2.46 0.01 cm
Different equipments have different uncertainties in their measurements.
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Chapter 1
Section 5
Significant Figures
In many cases, important physical quantities are obtained from measured values. Volume = l w h Mathematical operations Density = mass / volume Calculations need to be done on the basis of Significant Figure (S.F.) Rules R l for counting S.F. Rules f i SF Rules of mathematical operations on S.F. Implication of the word Significant. It is to have the correct degree of uncertainty in the resultant physical quantities.
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Chapter 1
Section 5
Rules for Counting Significant Figures 1- Nonzero integers are always counted as S.F. SF
Example: Give the number of S.F. for the following: 34 236 17296.1 12.1102 Exponential (Scientific) notation
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Chapter 1
Section 5
Rules for Counting Significant Figures 2- Zeros (leading zeros, captive zeros, and trailing zeros)
a) Leading zeros are not counted as S.F. Example: Give the number of S.F. for the following: 00121.1 0.0025
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Chapter 1
Section 5
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Chapter 1
Section 5
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Chapter 1
Section 5
Rules for Counting Significant Figures 3- Exact numbers are assumed to have an infinite number of S F S.F.
Examples: 3 Apples is 3.00000000 (zeros are all the way to ) 2 in 2r (the circumference of a cycle). cycle) 1 km = 1000 m 1 in = 2.54 cm
Dr. A. Al-Saadi
Definitions
Mathematical relationships
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Chapter 1
Section 5
Exercise
5.3004 m
0.120 1010 cm3
250.0 kg
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Chapter 1
Section 5
Mathematical Operations
Multiplication or division
4.56 1.4 4 56 1 4 = 6.38 6 38 6.4 64
2 S.F. (After correction) From calculator before correction
Number of S.F.
before correction
Dr. A. Al-Saadi
Chapter 1
Section 5
6.38
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Chapter 1
Section 5
Exercises
Perform the following mathematical operation and express the result to the correct number of significant p g figures:
Chapter 1
Section 5
Systematic error Precise but not accurate reproducible Good technique but needs calibration
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Chapter 1
Section 5
Accuracy: Agreement of a particular value (measurement) with the true value. Precision: Agreement among several values (measurements), not necessarily agreeing with the true value. value
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Chapter 1
Section 5
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Chapter 1
Section 5
Chapter 1
Section 6
Conversion Factors
Example 2:
How many inches are in 25.5 centimeters? 1 in 25.5 cm 10.0 in 2.54 cm
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Chapter 1
Section 6
?
Dr. A. Al-Saadi
1.63 L
Chapter 1
Section 6
0.25 megameters
0.2510 0 25106 m
100 cm 1 meters
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Chapter 1
Section 6
The Food and Drug Administration (FDA) recommends that dietary sodium intake be no more than 2400 mg y g per day. What is this mass in pounds (lb), if 1 lb = 453.6 g?
2400 mg
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Exercise
Perform the following mathematical operation and express the result to the correct number of significant p g figures:
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Exercise
Methodology to solve such problems: Start with the quantity given in the question. Use possible conversion factors to convert the unit of the given quantity in the question to the desired/needed unit.
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