Chemistry 1364
General Chemistry I
Chapter
1 - Introduction
Chemistry
n Study
of matter and the changes that matter can undergo
n Matter
n Has
mass/occupies space
n 3
phases
n solid
n gas
n liquid
(intermediate)
Matter
n Substance
n fixed
composition
n Au, H2O,
C6H12O6
n distinct
properties
n melting
point, color, vapor pressure
n The
two categories of matter are an element or a compound (more later)
n Two types of properties to describe matter
n physical
n no rearrangement of the atoms
n chemical
n atoms will rearrange to form new substances
n Changes
n physical
n chemical
n Mixtures
n heterogeneous
n homogeneous
(solutions)
n can
be of any phase
n CAN
BE SEPARATED BY PHYSICAL MEANS!
n filtration
n distillation
n chromatography
Problems 1, 3, 5
Elements and Compounds
n Elements
- cannot be decomposed by CHEMICAL means.
n 'Building
blocks' of the universe
n Abbreviated
by symbols (Table 1.2 - know)
n Compounds - decomposed by chemical means to
elements/other compounds.
n Law
of constant composition
n All
samples of a compound will have the same elements in the same ratio
Problems 7, 9, 11, 13, 15
Units of Measurement.
n Metric system - basis for SI system
n Units based on measurements of Earth
n Meter based on distance from equator to North Pole
n Heat based on energy to change water
n SI system
n Divides units into ‘base’ and ‘derived’
n Seven ‘base’ units
n All other units are a combination of the ‘base’ units
Base Units
n Mass
(kg)
n Length
(m)
n Time
(s)
n Electric
current (A)
n Temperature
(K)
n Luminous
intensity (cd)
n Amount
of substance (mol)
n All
other units - derived units
n volume
( length3 )
n weight
[ mass * length / time2 ]
n density
( mass / volume )
n etc...
Prefixes
n Defined
decimal amount of unit
n kilo
- unit x 1000
n centi
- unit x 0.01
n Know
prefixes from Terra to femto
n know
both abbreviation and unit
n milli-
n abbreviation
is m
n multiply
base unit by 0.001
n Difference
between MASS and WEIGHT.
n Mass
is a base unit
n Weight
is a derived unit (mass x acceleration)
n Mass
will not change with change in the gravitational field, but an object may
become ‘weightless’
Temperature
n Metric
- Celsius (non SI unit)
n 0
(freezing) to 100 (normal boiling) to define step size
n SI
- Kelvin
n same
'step size' as Celsius
n starting
point is absolute zero
n K
= OC + 273.15
n only
correct for starting point!
Temperature
n English - Fahrenheit
n Different step size (180 OF from freezing to boiling)
n Different starting point (32 OF = 0 OC)
n Must make TWO conversions
n Step size
n Starting point
n OF =
[(180/100) x OC] + 32OF
n OF =
[(9/5) x OC] + 32OF
n Rearranging, (OF - 32OF) x (5/9)
= OC
Volume
n volume
= length3
n Metric
unit was the Litre (L)
n Also
spelled liter
n still
commonly used for volume
n Metric
unit = dm3
n mL
- 0.001 L
n mL
= cm3
Units of Measurement
n Density
- mass/volume
n Density
D/N mean weight!!!
n Specific
gravity
n Density
of a substance / density of water
n Equal
to the density in g/mL
n Calculations
n Interconvert
between mass and volume using the value for density
n Intensive
& Extensive properties
Problems 17 -29 odd
Uncertainty in Measurements
n Exact numbers - no uncertainty
n numbers 'by definition’
n Integers
n ‘Counting numbers’
n Measurement - inexact numbers - ALWAYS
n Precision and accuracy
n NOT the same thing!
n I don’t care what Webster says!!
Precision and Accuracy
n Precision
- comparison of values to each other
n Accuracy
- comparison of values to a TRUE value
n Significant
figures
n use
to indicate first uncertain digit
n non-zero
digits are significant
Significant Figures
n Zero
n Between s.f.- significant (108)
n Right of decimal
AND right of s.f. - significant (10.0)
n left of first s.f. ARE NOT significant. (0.0153)
n Left decimal and right s.f. - maybe
n 1,000,000,000
n 5 significant figures
n Because I said so!
Significant Figures
n Use
scientific notation to clear up ambiguity
n X.YYY
x 10Z
n X =
1-9, Y=0-9
n Z -
any integer
Significant Figures in Calculations
n Multiplication
and Division
n fewest
number of significant figures in the calculation
n Addition
and Subtraction
n ‘least
significant’ decimal place
n Numbers
may contain too many significant figures after manipulation
n How
do we fix this?
Rounding
n Used
to make answer display the correct number of significant figures
n Decision
from first non-retained digit
n 0-4 round down (108.4 = 108)
n 6-9 round up (107.7 = 108)
n What
about 5
5
n non-terminal
- round up
n 107.513
= 108
n terminal
- round to the even
n 107.5
= 108
n 108.5=
108
n Round
at the end of a calculation, not in the middle!
Problems 31 - 37 odd
Dimensional Analysis
n Conversion
factors - equal to 1 (no units)
n can
use several sequentially
n can
use to cancel in numerator or denominator
n EXAMPLES
n Unit
conversions
n Density
problems
Problems 39-49 odd
Learning Goals
n Differentiate
among the three states of matter.
n Distinguish
between physical and chemical properties, as well as physical and chemical
changes.
n Distinguish
among elements, compounds, and mixtures.
n Give
the symbol for the elements in Table 1.2
n List
the basic SI units, the common metric prefixes and their meanings.
n Convert
temperature among OF, OC, and K.
n Perform
calculations involving density.
n Determine
the number of significant figures in a measured quantity.
n Express
the result of a calculation with the proper number of significant figures.
n Interconvert
metric and English system measurements using dimensional analysis.