Chem101 Chapter 01

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Chem101Chapter 01

• Chemical Foundations

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What is chemistry?
The science that explains
the properties of materials
how new materials may be made
the relationship between energy and chemical
reactions
how materials may be analyzed at the atomic and
molecular level (Macroscopic Microscopic.
A key concept is that chemists look for
explanations
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1.1Chemistry An overview

• Chemistry is fundamentally concerned with
• "How one substance changes to another"
• How plants grow by absorbing water and Carbon
  dioxide?
• How humans manufacture the proteins from the food
  we consume?
• .. and on and on
• A substance is composed of atoms, all universe is
  made of only 110 different types of atoms

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1.2 The Scientific Method

• It is a systematic approach to research that
  includes
• Making Observation
• Making a Prediction "Hypothesis"
• Doing Experiment to test the Hypothesis

Law summary of observed behavior
Theory model attempt to explain
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1.3 Units of Measurement

• Quantitative Measurement, consists of two parts
• a number and a scale (unit)
• In 1960, an international agreement get up a
  system of units called International System (SI-
  system) based on metric system.

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Prefixes are used to change the size of the unit
1.3 Units of Measurement
Table 1.2 Prefixes Used with SI Units Table 1.2 Prefixes Used with SI Units Table 1.2 Prefixes Used with SI Units
Prefix Symbol Meaning
Tera- T 1012
Giga- G 109
Mega- M 106
Kilo- k 103
Deci- d 10-1
Centi- c 10-2
Milli- m 10-3
Micro- m 10-6
Nano- n 10-9
Pico- p 10-12
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1.3 Units of Measurement

• Volume is not fundamental SI unit, but very
  commonly used in chemistry,
• SI derived unit for volume is cubic meter (m3)

1 m3 (10 dm)3 1000 dm3 1000 L
Used unit in liter 1dm3
1 L 1dm3 (10 cm)3 1000 cm3 (ml)
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1.4 Uncertainty in measurement

• Any measurement always has some degree of
  uncertainty. Uncertainty depends on the precision
  of measuring device.
• e.g., measurement of volume of a liquid using a
  buret
• the used liquid is about .mL

If 4 different people read the same volume we
might get
Person Result
1 22.2
2 22.1
3 22.3
4 22.0
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1.4 Uncertainty in measurement

• You have to record the certain digits and the
  first uncertain digit only.
• All digits together
• certain first uncertain
• are called
• " Significant Figures"
• The uncertainty in the last number must be
  assumed to be 1

Volume 22.2 0.1 ml
Example 1.1 What is the difference between the
measurements 25.00mL and 25mL?
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Precision and Accuracy
1.4 Uncertainty in measurement
Not Accurate Not precise

• Accuracy it is the agreement of a particular
  value with the true value.
• Precision it is the agreement among several
  measurements of the same quantity.

Not Accurate But precise
Accurate and precise
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Errors
1.4 Uncertainty in measurement
Large Random Error

• Random error it means that a measurement has an
  equal probability of being high or low.
• Systematic error error accurse in the same
  direction each item.

Small Random and Large Systematic Error
Small Random And NO Systematic Error
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1.5 Significant Figures (SF) and Calculations

• Rules for Counting Significant Figures
• It is important to be applied to get the
  uncertainty in the final results out of adding,
  subtracting multiplying ..etc.
• Nonzero integers, count as SF.
• Zeros
• - "Leading zeros are not significant. e.g.
  0.0025 (2 SF)
• - "Captive zeros Count as s.f. e.g.
  1.008 (4 SF)
• - "Trailing zeros count as s.f. eg. 100
  1.00 X 102 (3 SF)
• Exact numbers have an infinite number of SF
• e.g. 10 experiment, 5 apples, 8 books so on.
  ..
• Exponential notation
• it is used to unite large or small numbers in
  the correct sig.fig.
• e.g. 0.000060 ?convenient ? 6.0 x 10-5

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1.5 Significant Figures (SF) and Calculations

• Rules for SF in Mathematical Operations
• Multiplication / Division Final results have the
  same SF in the least precise measurement used in
  calculation.
• e.g. 4.56 x 1.4 6.38 (?)
• Addition / Subtraction Final results have the
  same number of decimal places as the least
  precise numbers
• e.g. 12.11 18.0 1.013 31.123 (?)

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1.5 Significant Figures (SF) and Calculations

• Note To get the correct total SF in the final
  results you may round off the results.
• Rules for rounding
• if the number to be removed is lt 5, the
  preceding digit stays the same.
• e.g., round 1.33 to 2 S.F. ? (?)
• Exercise 1.4
• a) 1.05 x 10-3 6.135 (.?)
• b) 21 13.8 (?)

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1.6 Dimensional Analysis

• conversion of a given results from one system
  unit to an other using "Unit Factor Method" or
  dimensional analysis.
• Means ?Multiply any expression by "1" will not
  change its value.
• Exercise 1.5
• A pencil is 7.00 in long, What is its length in
  centimeter?
• Solution
• what is the in/cm relation 2.54cm 1 in
• which unit is needed cm
• unit factor must has cm unit as nominator.
• i.e. 2.54 cm / 1 in 1 unit factor
• Multiply the length by the unit factor gives
• 7.00 in x 2.54 cm /1 in 17.8 cm
• 7.00 in 17.8 cm

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1.6 Dimensional Analysis

• Note
• Sometime you have to do multi-step conversion to
  get correct answer.
• Exercise 1.7
• A student has entered a 10.0 km race. How long
  is the run in miles?
• Solution km ? m ? yd ?mi
• 1 km 1000m, 1 m 1.09yd, 1760yd 1
  mi
• Results 10.0 km 6.22 mi

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1.7 Temperature
Engineering Science
Difference Is complicated
Difference Is in their zero

• Conversion
• Adjustment in the degree step
• Adjustment in the zero

Conversion Adjust the zero difference
Tc (TF-32oF) x 5oF/ 9oC TF (T0C x 9oF/5oC)
32oF
T(Kelvin) T(oC) 273.15
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1.8 Density

• It is the mass per unit volume of the substance.
• A property of matter that is often used by
  chemists.
• Density

Exercise 1.13 A chemist finds that 25.00cm3 of
a CD- cleaner has a mass of 19.625g at 20oC. The
following are the names and densities of the
compounds that might be the main
component Which of them is the most likely to
be the main component of the CD-cleaner? Solutio
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Chloroform 1.492 g / cm3 At 20oC
Diethyl ether 0.714 g / cm3 At 20oC
Ethanol 0.789 g / cm3 At 20oC
Isopropyl alcohol 0.785 g / cm3 At 20oC
Toluene 0.867 g / cm3 At 20oC
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1.9 Classification of matter

• Read (pp. 26-30)
• and Report (HW2)
• Define
• "Matter, Mixtures, Physical changes, Compound,
  and Element"
• Define
• "Distillation, Filtration, and Chromatography.

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What is this apparatus? What is its main opeation?