CHM 110

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CHM 110

• CHAPTER 1
• THE STUDY OF CHEMISTRY
• Dr. Floyd Beckford
• Lyon College

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A small piece of sodium which lived in a
test tube fell in love with the Bunsen
burner. Oh Bunsen, my flame. I melt whenever I
see you, the sodium pined. Dont worry. Its
just a phase you are going through, replied the
Bunsen burner.
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MATTER

• MATTER defined as anything that has mass
• and occupies space
• MASS defined as the amount of matter in an
• object
• An object or substance can be totally defined by
• its properties
• Two basic types

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• Physical
• - characteristics that are not related to the
• chemical makeup of the substance
• 2. Chemical
• - depends on the chemical composition
• Associated with properties are changes
• There are physical changes and chemical
• changes

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• May be classified further as extensive or
• intensive
• EXTENSIVE properties depend on the amount
• of sample
• INTENSIVE properties do not depend on
• sample size

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STATES OF MATTER

• Three common states solid, liquid, gas
• The states are usually defined by the
• arrangements of their particles
• Solids have well-ordered particles in close
• contact with each other
• Liquids have particles that are close enough
• together to allow the substance to flow

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• Gases the particles are very far apart from
  each
• other and move randomly

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ENERGY

• Energy defined as the ability to do work
• Two fundamental categories
• Potential energy - the energy an object
• possesses by virtue of its position or
  composition
• 2. Kinetic energy - the energy of an object due
  to
• its motion

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• Total energy Potential Kinetic
• of an object Energy
  Energy
• Energy changes accompany chemical and
• physical changes
• But total energy is constant
• Law of Conservation of Energy - energy can
• neither be created nor destroyed it can only be
• converted from one form to another

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MEASUREMENT

• All measurements in science has two parts a
• number and a unit
• In chemistry SI Units are used for measurement
• There are 7 fundamental units
• Mass ? kilogram (kg)
• Length ? meter (m)
• Temperature ? kelvin (K)

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• Amount of substance ? mole (mol)
• Time ? second (s)
• Sometimes the units are too big or too small
• Prefixes are then required
• milli - 1/1000 (10-3)
• kilo - 1000 (103)
• nano 1/1 000 000 000 (10-9)

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DIMENSION ANALYSIS

• A method for going from one unit to another
• using a conversion factor
• Original quantity x CONVERSION FACTOR
• Equivalent quantity
• Units may be multiplied or divided
• Converting between inches and feet
• 12 in 1 ft

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Convert 100 km to miles given 1 km 0.6214 mi

• Any number of conversion factors may be used to
• carry out a conversion

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• Recall the seven fundamental SI units
• All other units are derived from those
• Some common units
• MASS - has SI units of kilograms, kg
• - a fairly big unit typically grams or
  milligrams
• are used
• 1 kg 1000 g 1 000 000 mg

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• Mass must be differentiated from weight
• Weight is a force related to the gravitational
• field acting on the object
• - so weight varies from place to place
• Mass on the other hand is constant

• Balances measure mass not weight

• VOLUME - a common derived property

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• Has SI units of m3
• Smaller units of liters, L and milliliters, mL
• are used
• 1 m3 1000 L
• Another common volume unit cm3
• 1 cm3 1 mL

• What kind of properties are mass and volume?

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• DENSITY the density of an object is defined
• as the ratio of its mass to volume

• - more likely to see g/cm3 or g/mL
• Density is an example of an intensive property
• (at a particular temperature)

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TEMPERATURE

• Temperature is a measure of how hot or cold an
• object is
• - has to be compared to something
• HEAT is a form of energy the flow of which
• depends on the temperature difference between
• two bodies
• Heat ? extensive temperature ? intensive

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• Temperature may be measured with any of 3
• units
• - degree Fahrenheit (F), degree Celsius (C)
• and the kelvin (K)
• The kelvin is the SI unit
• The scales differ in the size of the respective
  unit
• and/or the definition of the zero point

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• The C and K are the same size - but the scales
  
• are different
• Celsius scale water freezes at 0 C
• boils at 100 C
• Kelvin scale water freezes at 273.15 K
• boils at 373.15 K
• So
• 0 C 273.15 K

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• On the Fahrenheit scale water freezes at 32 F
• water boils at 212 F
• - difference is 180 units
• So the C is bigger than the F
• 100 Celsius units 180 Fahrenheit units

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• Conversion of Celsius ? Fahrenheit
• (i) size correction, and
• (ii) a zero point correction

• For C ? F do (i) then (ii)

• For F ? C do (ii) then (i)

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98.6 F ? C ? K
37 C
310 K
158 C ? F
316 F
375 K ? F
102 C
216 F
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NUMBERS

• ACCURACY refers to how close a measurement
• is to the true value
• PRECISION refers to repeatability - how well
• a number of independent measurements agree
• with one another
• The total number of digits in a measurement is
• called the significant figures a reflection of
  the
• uncertainty (error)

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• Rules for significant figures
• 1. Zeroes in the middle of a number are always
• significant
• 2. Zeroes at the beginning of a number are NOT
• significant
• 3. Zeroes at the end of a number and after the
• decimal point are always significant
• 4. Zeroes at the end of a number and before the
• decimal point may or may not be significant

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• Rounding numbers
• In a multiplication or division, the answer
  cannot
• have more significant figures than any of the
• original numbers
• In a addition or subtraction, the answer cannot
• have more more digits to the right of the decimal
• point than any of the original numbers

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• In rounding off
• First digit removed
• dropping it
• 2. First digit removed is ? 6 round up by adding
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• 2.309 86 x 10-4 (to 5 sig. figs) ? 2.309 9 x
  10-4
• 3. First digit removed 5 with more non-zero
• digits following it round up
• 3.442 508 (to 4 sig. figs) ? 3.443

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4. First digit removed 5 with nothing following
it (i) round up if the preceding digit is
odd 4.7475 ( to 4 sig figs) ? 4.748 (ii) round
down if preceding digit is even 4.7465 (to 4 sig
figs) ? 4.746
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• Consider the following
• 2.54 cm 1 in or 60 min 1 h
• The number 2.54 is known with absolute
• certainty it has an infinite number of
  significant
• figures
• Such numbers are called exact numbers

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• Precision and accuracy are linked to errors
• 1. Systematic errors
• - values are either all higher or all lower
• than the actual value
• 2. Random errors
• - some values are higher and some are
• lower than the actual value
• Systematic errors minimized by using calibration