Week 1 -2
CHEMISTRY and
MEASUREMENTS
Here
GENERAL
is where your
CHEMISTRY
presentation
begins
Origin of Chemistry
Alchemy
Earthen Metals
The Art
Chemistry
chemeia ( greek word)
Definition
a science that deals with the
composition, structure, and properties
of substances and with the
transformations that they undergo
Properties of Substances
Physical
• Form of appearance or
substance.
• Fundamental nature
stays the same.
Chemical
•
•
Combines or is converted
to another substance.
Cannot be reverted to
original state.
Physical Changes
Cutting, bending, dissolving, freezing, boiling, and melting are some
examples of physical changes.
Chemical Changes
Combustion, rotting, rusting, digestion, and cooking are some examples
of chemical changes.
Types of Substances
Pure
•
Cannot be separated into
other kinds of matter by
any physical means
Mixtures
•
Combination
of
pure
substances
but
not
chemically combined.
Pure Substances
H
H
H
O
Elements
O
Compounds
Mixtures
Homogeneous
Heterogeneous
What is the
relationship
between Chemistry
and
Measurements?
Macroscopic
Microscopic
Measurement
•
•
Provide the macroscopic information that is
the basis of most of the hypotheses,
theories, and laws that describe the behavior
of matter.
Provides two kinds of information: the size or
magnitude of the measurement (a number or
quantity); and a standard of comparison for
the measurement (a unit).
Which is correct?
International System of Units
•
•
•
From
the French, Le
Système
International
d’Unités.
The standards for these
units
are
fixed
by
international agreement.
Have been used by the
United States National
Institute of Standards and
Technology (NIST) since
1964.
SI Units
m
kg
s
Length
Mass
Time
meter
kilogram
second
K
A
mol
Temperature
Electric Current
kelvin
ampere
Amount of Substance
mole
Significant Figures
Non-zero digits
3,459 = Four SF
Any zeros between two significant digits
3008 = Fours SF
A final zero or trailing zeros in the decimal portion
ONLY
5. 6890 = 5 SF; 0.00088= 2 SF
How many SF are there in each given?
4.5687
5 sf
300,008.005
7 or 9 sf
20350.00
5 sf
Scientific Notation
Use to denote numbers that are
too big or small.
Move the decimal point to the left
6400 -> 6.4 x 10
Positive Integer
3
Move the decimal point to the right
0.0064 -> 6.6 x 10
Negative Integer
-3
Convert the following into scientific notation.
0.000045637
4.56 x 10^ -5
13452.89000
1.35 x 10 ^4
456,908
4.57 x 10 ^5
Unit Prefixes
PREFIX
femto
SYMBOL
f
FACTOR
10−15
pico
p
10−12
nano
micro
milli
centi
deci
kilo
mega
giga
tera
n
µ
m
c
d
k
M
G
T
10−9
10−6
10−3
10−2
10−1
103
106
109
1012
Unit Conversion
6 kgs
7 lbs
01
Mass
1kg
= 1, 000,000 mg
= 100,000 centigrams
= 10,000 decigrams
= 1000 grams
= 100 decagrams
= 10 hectograms
Factor Label Method
Example: Convert 500
grams to kilograms
Example 1: Convert 500 grams to kilograms
Step 1: Identify what is needed to be converted
500 grams -> kilograms
Example 1: Convert 500 grams to kilograms
Step 2: Identify the conversion factor needed to be
used.
1 kilogram-> 1000 grams
Note: For larger numbers, you can use the scientific exponent form.
Example 1: Convert 500 grams to kilograms
Step 3: Use the factor label method to convert the
given.
(Conversion factor)
500 g x Unit to be converted
Unit to be removed
(same unit as the given)
500 g x 1kilograms = 0.5 kilograms
1 gram
/
/
Note: For larger numbers, you can use the scientific exponent form.
Factor Label Method
(Multiple Conversions)
Example: Convert 246
inches to feet and cm
Example: Convert 246 inches to feet and meter.
Step 1: Identify what is needed to be converted
246 inches -> feet -> meter
Example: Convert 246 inches to feet and meter.
Step 2: Identify the conversion factor needed to be
used.
1 inch= 2.54 centimeters
1 foot= 12 inches
1 meter= 100 cm
Note: For larger numbers, you can use the scientific exponent form.
Example: Convert 246 inches to feet and meter.
Step 3: Use the factor label method to convert the
given.
(Conversion factor)
246 in x Unit to be converted
Unit to be removed
(same unit as the given)
/
246 inches
1 foot
= 20.5 ft
12 inches
/
Note: For larger numbers, you can use the scientific exponent form.
Example: Convert 246 inches to feet and meter.
Step 3: Use the factor label method to convert the
given.
1
meter
2.54
cm
x
= 6.25 meter
246 inches x
100 cm
1 inch
/
/
Note: For larger numbers, you can use the scientific exponent form.
Common Conversion
Factors
Length
Mass/ Volume
1 inch (in.) = 2.54 cm
1 liter (l) = 1000cm3
= 1.057 quart (qt)
= 61.02 in3
= 0.03532 ft3
1 foot (ft.) = 12 inches
1 cubic meter (m3) = 1000 L
= 35.32 ft3
1 mile = 1.609 km
1 kilogram (kg) = 2.2046 pounds
(lb)
1 meter= 39.37 inches
Errors in measurement
Indeterminate error
Relative Error
•
•
•
•
Caused by uncontrollable variables, which can not be
defined/eliminated.
Rounding off, estimations,
The ratio of the absolute error of the measurement to the
actual measurement.
Determines the magnitude of the absolute error in terms
of the actual size of the measurement.
Sample Problems
Sample Problem 1: Classify the following changes as
physical and chemical changes
a. Melting of water
b. Rusting of iron
c. Boiling of sugar to make syrup
d. Paper burning
e. Magnesium dissolved in acid
Sample Problem 2: How many a.kilometers, b. meters, c.
centimeters, d. milliliters are there in 0.800 miles. Show in 3
significant digits.