Transcript Ch. 1_Chemical Foundations PPT

. Do Now:
1. Differentiate between qualitative and
quantitative observations/data.
2. True or False (explain why): A theory can be
proven correct or incorrect
1.1 Chemistry: An Overview
 Considered the “central” science
 ALL matter and energy transformations are based on
interactions between atoms and molecules
 Macroscopic vs. submicroscopic views
 Science: a process for understanding the natural world
and its changes
1.2 Scientific Method
 Making observations
 Qualitative Observations - observations made by using
your senses (does not involve a number)
 Quantitative Observations - observations made by
measuring (involves a number and a unit)
 Formulating hypotheses
 hypothesis - a possible explanation for an observation
 Performing experiments
 experiments - performed to test the hypothesis.
Experiments will either support or disprove your
hypothesis.
 Forming a theory - set of hypotheses that agree with
observations over the test of time. Helps create a model.
1.3 Units of Measurement
 Metric System: ALL measurements in this course are
expected to be reported in the metric system
 Measurements
 Number and Scale (units) are both essential
 "The number without the units is worthless!“
SI system
 Important SI Units for Chemistry
 Mass  kilogram kg
 Length  meter  m
 Time  second  s
 Temperature  Kelvin  K
 Amount of Substance  mole  mol
 Volume  liter  L
SI Prefixes










Mega
M
1,000,000
Kilo
K
1,000
Hecto
H
100
Deka
D
10
Deci
d
.1
Centi
c
.01
Milli
m
.001
Nano
n
.000 000 001
Pico
p
.000 000 000 001
**KNOW TABLE 1.2 (page 9)**
106
103
102
100
10-1
10-2
10-3
10-9
10-12
1.4 Uncertainty in Measurement
 Every measurement always has some degree of uncertainty.
 When measuring it is always important to record the certain
digits (those that are marked on the measuring device) and
the
 first uncertain digit (not marked on the device and the number is
guessed at).
 Accuracy - refers to the agreement of a particular value
with the true value.
 Precision - refers to the degree of agreement among
several measurements of the same quantity.
 Random error - means that a measurement has an equal
probability of being high or low.
 Systemic error - this error occurs in the same direction
each time; it is either always high or always low.
1.5 Significant Figures and
Calculations
 Nonzero integers - nonzero integers always count as
significant figures.
 Zeros - depending on the type of zero, it will determine
weather the zero counts or does not.
 Leading zeros - are zeros that precede all the nonzero digits.
these do not count as significant figures, they are considered
place holders.
 Captive zeros - are zeros between nonzero digits. These
always count as significant figures.
 Trailing zeros -are zeros at the right end of the number.
They are significant only if the number contains a decimal
point.
 Exact numbers - numbers that were not measured but
determined by counting. These can be assumed to have
an infinite number of significant figures.
Mathematical Operations
 For multiplication or division - the number of
significant figures in the result is the same as the
number in the least precise measurement used in
the calculation.
 For addition or subtraction - the result has the
same number of decimal places as the least
precise measurement used in the calculation.
Rounding
 In a series of calculations, carry the extra digits
through to the final result, then round.
 If the digit to be removed  is less then 5, the preceding digit stays the same.
 is equal to or greater than 5, the preceding digit is
increased by 1.
1.6 Dimensional Analysis
 method used to change from one system of units to
another.
 Converting from one unit to another
 To convert from one unit to another, use the equivalence
that relates the two units.
 Derive the appropriate unit factor (equivalence factor)
by looking at the direction of the required change (to
cancel the unwanted units)
 Multiply the quantity to be converted by the unit factor
to give the quantity with the desired units.
1.7 Temperature
 Know the relationship and conversion between the three
systems for measuring temperature
 Kelvin
 Celcius
 Farenheit (oF)
(K)
(oC)
 Celsius (°C) and Kelvin (K)
 Kelvin = Celsius + 273.15
 Celsius = Kelvin - 273.15
 Size of the temperature unit (degree) is the same
 Fahrenheit
 TC = (TF - 32°F)(5°C/9°F)
 TF = TC x (9°F/5°C) + 32°F
1.8 Density
 Derived unit
 Based on relationship between mass and volume
 D = M/V
 Dependent on temperature
 WHY?
 NOT dependent on amount or quantity of sample used
1.9 Classification of matter
 Matter
 Anything that occupies space and has mass
 States of Matter
 Solids - rigid, fixed volume and shape
 Liquids - definite volume, no specific shape
 Gases - no fixed volume or shape, highly compressible
 Mixtures - Matter of variable composition
 Heterogeneous mixtures

Having visibly distinguishable parts
 Homogeneous mixtures (solutions)

Having visibly indistinguishable parts
 Components of Mixtures can be Separated by Physical
Means
 Distillation-difference in volatility
 Filtration-solid/liquid
 Chromatography—difference in polarity
 Pure substances
 Elements

Cannot be decomposed into simpler substances by physical or
chemical means
 Compounds
 Constant composition
 Can be broken into simpler substances by chemical means, some
physical means
HOMEWORK 1A student performed an analysis of a sample for its
Iodine content and got the following results.
19.3%, 21.2%, 18.7% and 20.4%
The actual value is 20.3%.
What can you say about the student’s accuracy and
precision?
What can you say about the cause(s) for any error?
2. Is the boiling of water a physical or chemical change?
Explain
3. Textbook Questions 29a,b, 31a,b, 33a-d, 35c, 43, 45
1.
Homework 2
 Textbook Questions, Chapter 1
# 15, 47, 53, 59, 63, 67, 69, 77,