Download Chemical Foundations

Chemical Foundations
Unit 1
Why is Chemistry Important?
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New materials
New pharmaceuticals
New energy sources
Food supplies
Help the environment
Can you think of others?
What is Chemistry?
A central science that deals with the materials
of the universe and the changes they
undergo.
Biology
Physics
Chemistry
Earth
Sciences
The Scientific Method
Observation
Hypothesis
Experiment
Summary of
What
(measurable)
Happens
Ex: law of
conservation of
mass
Theory
(model)
Theory
Modified
As
needed
Prediction
Experiment
A Theory (model)
attempts to explain why
it happens
Measurement & Calculation
Qualitative
Quantitative
Overview:
• Deals with descriptions
• Data can be observed but not
measured
• Colors, textures, smells etc.
•Qualitative -----Quality
Overview:
• Deals with numbers
• Data which can be measured
• Length, Height, volume, weight, speed,
time, temp
• Quantitative-----Quantity
Example: Oil Painting
• Blue & green paint
• Gold frame
• Masterful brush strokes
Example: Oil Painting
• 10” x 14”
• surface area 140 in2
• Weight: 8.5 pounds
Measurement
• Quantitative observation.
• Has 2 parts – number and unit.
 Number tells comparison.
 Unit tells scale.
Measurement
Scientific Notation
• Technique used to express very large or very small numbers.
• Move the decimal so that one non zero integer is to left
• If you moved to the left then the exponent is positive (number is big)
• If you moved to the right then the exponent is negative (number is
small)
Scientific Notation
• Distance from the sun to the earth is
91,000,000 miles
91,000,000 =
9.1 x 107 mi
A carbon nanotube has a width of
.00000000705 m.
0.00000000705 =
7.05 x 10-9 m
Points to Remember
• If original number greater than 1, exponent
is positive
91,000,000 = 9.1 x 107 miles
• If original number is less than 1, the
exponent is negative
0.00000000705 = 7.05 x 10
-9
m
Units of Measurement
SI System: based on the metric system and units
derived from the metric system.
Physical Quantity
Name of Unit
Abbreviation
Mass
Kilogram
kg
Length
Meter
m
Time
Second
s
Temperature
Kelvin
k
Electric Current
Ampere
A
Amount of substance
Mole
mol
Luminous intensity
Candela
cd
Units of Measurement
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Prefixes are used to change the size of the unit.
Volume
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Measure of the amount of
3-D space occupied by a
substance.
SI unit = cubic meter (m3)
Commonly measure solid
volume in cm3.
1 mL = 1 cm3
1 L = 1 dm3
Uncertainty in Measurement
• The length of the pin occurs at about 2.85 cm.
 Certain digits: 2.85
 Uncertain digit: 2.85
Uncertainty in Measurement
Certain digits: 21. ml
Uncertain digit:
21.7 ml
Uncertainty in Measurement
1. Instruments are never completely free of flaws
2. Measuring always involves some estimation
Precision and Accuracy
Accuracy: agreement of a particular value with the accepted
value.
Precision: agreement among several measurements of the
same quantity (reproducibility).
SIGNIFICANT FIGURES
All digits known with certainty, along with the first
uncertain digit
The last digit of a measurement expression is
uncertain.
Significant Figures
Rules for counting Significant Figures:
1. Nonzero integers always count!
2. Zeroes (3 classes):
a. Leading zeroes do not count (place holders)
b. Captive zeroes do count
c. Trailing zeroes count if there is a decimal point
0.0065
4005
65.00
Leading!
Captive!
Trailing!
3. Exact numbers, have an infinite number of significant figures
because they are counts not measurements. Therefore, if a number is
exact, it DOES NOT affect the accuracy of a calculation nor the
precision of the expression
Ex. 9 pencils, 24 students, 1 ft = 12 in.
Let’s try it
ATLANTIC-PACIFIC
Pacific
1402 =
1.042 =
142 =
0.1402 =
4
4
3
4
If decimal Present, start counting
non-zeros from the Pacific side
sig
sig
sig
sig
fig
fig
fig
fig
Atlantic
If decimal Absent, start counting
non-zeros from the Atlantic side
Rounding Numbers
Perfectly Round!
Rules for Rounding
• 1. When the 1st digit after those you want to retain is 4 or
less, that digit and all others to the right are dropped
• 2. When the 1st digit after those you want to retain is 5 or
greater, that digit and all others to the right are dropped
and the last digit retained is increased by one
Examples
1. Keep 3 sig fig
*hint: count 3 then look to the right
105.29 = 105
2. Keep 4 sig fig
*count 4 then look to the right
10.87519 = 10.88
3. Keep 3 sig fig
*count 3 then look to the right
1067 = 1070
4. Keep 5 sig fig
*count 5 then look to the right
1042.567 = 1042.57
Significant Figures & Calculations
(2.5)
Rules for Significant Figures in calculations:
1. For multiplication or division: the answer is the same as the
LEAST precise number in the calculation.
67.64 grams x 43 grams =
4 Sig Figs
2 Sig Figs
2908.52 grams2
Answer must have 2 Sig Figs
Count from the left starting with
2
2908.52
grams
the first Integer
Use the first number past to
2
Answer
=
2900
grams
round (up if 5 or more)
Significant Figures & Calculations
Rules for Significant Figures in calculations:
2. For addition or subtraction: the answer has the same number of
decimal places as the least precise measurement in the calculation.
37.113 grams
115.02 grams
6.175 grams
158.308 grams
3 decimals
2 decimals
3 decimals
The answer MUST have only 2 decimal
places!
Count the two then use the one right
after to round. (up if 5 or more)
158.308 grams
Answer = 158.31 grams
Significant Figures & Calculations
(2.5)
Rules for Significant Figures in calculations:
3. Rounding: DO NOT round until all calculations are
completed. Use only the first number to the right of the
last significant figure.
How many Sig Figs?
1. 0.0050 L = 2
2. 0. 00012 kg = 2
3. 83.0001 L = 6
4. 875,000 oz = 3
5. 78,002.3 ng = 6
6. 70,879,000 ml = 5
7. 23,001.00 lbs = 7
8. 1.089 x 10-6 L = 4
9. 1.34000 x107 m = 6
10.1,000,000,000 g = 1
PRACTICE
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6.45 x 103 cm
.0089 m2
5.072 x 102 L
8.65 x 106 m
7650 g
.0000072103 km
20,350,000 mg
2.2 x 101 ml
550,050 ug
8.56 x 104 cm
.0012340400 m
% Error
Percent Error =
Experimental
-value
Accepted
Value
Accepted Value
X 100
Gold has a density of 19.3 g/cm3. A student
lab group determines its density to be 18.0 g/cm3.
What is the percent error of the students?
Experimental value – Accepted value x 100 = % Error
Accepted value
18.0 – 19.3
19.3
X 100 =
1.3
19.3
X 100
= 6.7%
You Try
Cooper measures the volume of a 2.50 L container
to be 2.63 L. What is the percent error of
Cooper’s measurement?
2.63 L – 2.50 L
2.50 L
X 100 =
.13 L
2.50 L
= 5.2 %
Temperature
Definition:
Measure of the average kinetic
energy of the molecules
(atoms).
(Higher temperature, molecules move
faster, higher kinetic energy)
b. Measured with a
thermometer.
c. Units: oC or K
Temperature Scales
Celsius(oC)
Farenheit(oF)
100°
Boiling point
of water
100 U
100 U
373°
273°
Absolute zero
212°
180 U
Kelvin (K)
0°
Freezing point
of water
-273°
32°
0°
-459°
Temperature Conversions
• °K = °C + 273
oF
= 1.8 oC + 32
• Convert:
199. °C to °K
50. °K to °C
= 472 K
= -223 °C
32oC to oF = 90. oF
List as many properties as you can think of that would
help you identify this substance as water.
Clear
Odorless
Liquid
pH of 7
Boiling Point: 100 C
Freezing Point: 0 °C
Density: 1 g/cm3
Water
Which of these properties can be determined
without altering the IDENTITY of the
substance?
Color, odor, freezing point, boiling point, density, state
physical properties.
These are _____________
Other examples of physical properties
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Color
Odor
Boiling point
Freezing point
Density
State
Taste
Hardness
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Texture
Streak
Cleavage
Luster
Magnetism
Conductivity
Ductility
Solubility
3. Properties which are determined by altering
the identity of the substance
chemical
are ________________
properties.
Some examples of chemical properties
are
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Flammability
pH
Ability to rust
Reaction with air
Reaction with water
CHARACTERISTICS - STATES OF MATTER
State
Density Compress- Shape
Volume
ibility
Solid
High
Not
compressible
Definite –
holds its
own shape
Definite
Liquid
High
Only
slightly
Assumes
shape of
Container
Definite
Gas
Low
Highly
Assumes
shape of
Container
Not
definite
ELEMENTS (What ARE they?)
a. Pure substances made of only one kind of atom
b. Cannot be broken down by CHEMICAL MEANS (heat,
light, electricity)
c. Number of known elements: 118
d. # 1 – 92: NATURAL elements
# 93  TRANSURANIUM elements
Zinc (Zn), Copper (Cu), Lead (Pb), Carbon (C), Sulfur (S)
COMPOUNDS (What ARE they)?
a. 2 or more elements chemically combined in a
fixed ratio
b. Can be separated only by chemical means (heat,
light, or electricity)
 Ex. Carbon dioxide, carbon monoxide, water, salt
(NaCl), rust, sugar, baking soda
Oxygen
Hydrogen
Hydrogen
A newly formed compound will have properties
that are uniquely different from the elements that
compose it.
Pure Substance (Substance)
Has a definite chemical composition
a. Represented by a chemical formula
b. Includes:
1. Elements —
C, Fe, H2, Au
2. Compounds —
Salt (NaCl), water (H20)
Mixtures
a. Physical blend of two or
more substances, each
retaining its own
properties
Ex. Salt water, air, granite
b. Components exist in
varying proportions
c. When mixed, no evidence
of chemical change
Two types of Mixtures
1. Homogeneous
2. Heterogeneous
Homogenous Mixtures
(or Solutions)
a. Components are uniformly
distributed
b. Ex. salt water, air, black
coffee, tea, soda, alloys
(brass, bronze, sterling
silver)
c. Any portion has the same
properties as any other
portion
Heterogeneous Mixtures
Have parts with
different properties
Ex. Granite, salad, salad
dressing, fog, milk
All mixtures:
a. can be separated by PHYSICAL means:
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Evaporation
Filtering
Distillation
Dissolving
Chromatography
Centrifuging
Magnetizing
Crystallization
Chemistry is
about change!
Categorize the following as chemical or
physical change:
– Rusting, burning, crushing, boiling, dissolving,
evaporating, souring, melting, freezing,
fermenting, magnetizing
Physical Changes
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Magnetizing
Crushing
Boiling
Evaporating
Dissolving
Melting
Freezing
Chemical Changes
____________
• Changes that DO alter the identity of a
substance.
Examples of Chemical Change
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Rusting
Burning
Souring
Fermenting
Important Distinction!
Physical CHANGE
Boiling
Freezing
Dissolving
Physical PROPERTY
Boiling point
Freezing point
Solubility
Chemical CHANGE
Burning
Rusting
Chemical PROPERTY
Flammability
Ability to rust