Transcript chem100c1f

Chemistry 100 Fall 1999
Dr. Upali Siriwardane
CTH 311 Phone 257-4941
Office Hours: Tu,Th, F 8:00-10:00 a.m.
M, W 1:00-3:00 p.m.
Test 1 : Chapters 1, 2:
September 27
Test 2: Chapters 3, 4:
October 18
Test 3: Chapters 5, 6:
November 10
Make-up, Comprehensive, November 15
KEY CONCEPTS
What is chemistry?
Physical and chemical changes.
Physical and chemical properties.
Categories of matter.
Separating Mixtures.
Scientific Method.
Scientific Measuremen
Observation. & Uncertainty.
Significant figure.
Precision.
Accuracy.
Significant figures in
calculations.
Unit Conversions.
Temperature Conversions. Unit conversion
method.
What is chemistry?
• Chemistry deals with non-reversible
changes of matter.
• Chemistry explains using atoms and
molecules.
• Chemical Concepts and Models
improve your problem solving skills
• Chemistry is a Central Science
What is Matter
• Matter: Anything that has a
mass and volume. The
opposite of matter is energy.
• Matter and Energy is
intertwined.
Hierarchy of Matter
Mixtures
Heterogeneous
Homogenous
Pure Substances
Compounds
Elements
Atoms
Nucleus
Electrons
Neutrons
Protons
How do you Separate
Mixtures?
•
•
•
•
•
•
Flotation: based on density
Filtration: Solid- liquid
Distillation- Liquid-liquid
Magnetic Separation- MagneticChromatography:
1) Paper 2) Column 3) Gas
What is a Substance?
• Substance:
• Substance is what matter is made
up of. Substances are either
elements or compounds.
• Pure substances:
• have characteristic properties such
as color, boiling point and
reactivity.
What is an Element
• Element: Elements are substances
made up of only one kind of atoms.
• Eg. oxygen- O2,
•
iron-Fe,
•
copper-Cu.
What is a Compound?
• Compounds: Compounds are
substances made up of more than
one kind of atoms.
• E.g. Water -H2O.
Properties of Substances
• Physical properties:
• Physical properties are descriptions of
matter such as color, density, viscosity,
boiling point, and melting point.
• Chemical properties:
• Chemical properties relates to the
changes of substances making up the
matter. For example, corrosiveness,
Flammability
Type of Changes
• Physical change:
• A change in the state of matter. It does
not involve a change in the substances.
E.g. melting of wax and water.
• Chemical change:
• A change involving at least one of the
substances making the matter. E.g.
Electrolysis of water, formation of rust:
reaction of iron and oxygen to from
iron oxide.
Scientific Method.
• A method common to all sciences
• Four Basic Steps:
•
a) Experiment
•
b) Results
•
c) Hypothesis
•
d) Further experiments to test
•
hypothesis
Measurement
• Measurements or observations are made
• using our physical senses or using scientific
instruments.
• 1) Qualitative measurements.
• Changes that cannot be expressed in terms
of a number.
• 2) Quantitative measurements.
• expressed in terms of a number and an unit.
Measurement
• Number
• a) Uncertainty (significant figures)
• b) Precision
• c) Accuracy
• Unit
• a) basic units
• b) derived units
Significant Figures:
• indicate the uncertainty
• rules to obtain the significant figures
• Significant
• 1) Non-zero digits are always significant.
• 2) Any zeros between two significant digits
3)Trailing zeros in the decimal portion
• Not significant
• 1) leading zeros
• 2) trailing zeros in whole numbers (use
scientific notion to avoid confusion.
• 3) Exact numbers: unit definition has an
unlimited number of sig. digs. 1 ft = 12 in
• Rounding off: superfluous digit(s) is/are
• 1) less than 5, the preceding figure is
retained.
• 2. Greater than 5, the last place retained is
increased by one
• 3. Iof the digit 5 exactly rounded off to a
even.
Examples
•
•
•
•
•
•
0.00341........3 sig. digs.
1.0040.........5 sig. digs.
0.00005........1 sig. digs.
65000.......… 2 sig. digs. 6.5 x 104
40300..........3 sig. digs.
200300.........4 sig. digs. 2.003 x 105
Significant figure
in Calculations
•1. Adding/ subtracting numbers.
•2. In multiplication and division
•3. The root or power of a number
• 4. Exact Numbers
Adding/ subtracting
•Arrange the numbers in
columnar form. Use most
uncertain digit to round
off the answer.
multiplication and
division
•the result should have
no more sig. digs. than
the factor having the
fewest number of sig.
digs.
Root or Power of a
number
• should have as many sig.
digs. as the number itself.
• Exact Numbers: Numbers
coming from definitions such
as 12 in = 1 foot. They are
not considered in Sig. Fig.
Calcualtions.
a) 10.26 + 0.02 + 450 = 460.28 = 460
2 significant figures
ones place in 450 has the greatest uncertainty
b) 3.56 x 1.2 = 4.272 = 4.3
2 significant figures
c)
356.001 x 15.43
-------------------- = 45.58585 = 45.59
120.5
4 significant figures
c) (2.8 + 3.4) (2.35 - 4.1) = 6.2 x (-1.75) =
6.2 x (-1.75) = -10.85 = -11
2 significant figures
UNITS
Base Quantity Base Unit
Length meter
Mass kilogram
Temperature kelvin
Time second
Amount of Substance mole
Electric current ampere
Light intensity candela
Factor Prefix
(m)
(kg)
(K)
(s)
(mol)
(A)
(cd)
10 6 mega
103 kilo
10-1 deci
10-2 centi
10-3 milli
10-6 micro
10-10 Angstrom
10-9 nano
10-12 pico
(M)
(k)
(d)
(c)
(m)
()
(Å)
(n)
(p)
CONVERSION
FACTORS
• convert from one
unit to another
• Length:1 km = 10 3 m; 1 ft = 12 in;
• 1 in = 2.54 cm;1 cm = 10-2 m; 1 yd = 3
ft;
• 1 m = 39.37 in
• 1 mm = 10-3 m 1 mile = 5280 ft ;
• 1 mile = 1.609 km;1 nm = 10-9 m
• Volume:1 m3 = 106 cm3 ;1 gal = 4 qt = 8
pt; 1 ft 3 = 28.32 L;1 cm3 = 1 mL; 1 qt =
57.75 in3 ;1 L = 1.057 qt
• Mass:1 kg = 103 g; 1 lb = 16 oz; 1 lb =
453.6 g; 1 mg = 10-3 g; 1 short ton
=2000 lb
• 1 g = 0.03527 oz;1 metric ton =103 kg
Unit Conversion Method
Dimensional(Unit) Analysis
• Normally calculations are done using an
equation.
• Method of calculations using units
• a) write the measurement you want
convert
• b)Find all conversion factors needed
• c) arrange all conversion factors to cancel
and to get units of the answer
Factor Label Method
•
•
•
•
•
•
•
•
3 km ---> ? m ;
conversion factor: 1 km = 1000m
1 km
1000m
------or -------1000m
1 km
1000 m
3 km x ----------- = 3000 m
1 km
Speed of light is 3.00 x 108 m s-1 .
Convert the speed of light to miles per
year (1 mile = 1.61 km).
.
8
3.00 x 10 m
-4
6.21 x 10 mile
31536000 s
= 5.87 x 1012
mile/yr
1s
1m
1 yr
Temperature Conversions
• oF -- > oC ; C = 5/9 (F - 32)
• oC -- > oF ; F =9/5 C + 32
• oC -- > K ; K = C + 273.15
• Human body temperature is 98.6 oF.
Convert this temperature to oC and K
scale
• oC = 5/9 (98.6 - 32) = 5/9 (66.6) = 37.0
• oC--> K = 37.0 oC +273.15 = 310.2 K
Density Calculations
• Equation method:
• Density = mass ÷ volume; d = m/v
• Factor Label method:14.2 g -- > ? cm3
conversion factor
•
2.70 g
1 cm3
•
-------- or -----•
1 cm3
2.70 g
• 14.2 g x 1 cm3
• --------------------- = 5.26 cm3
•
2.70 g