Transcript Chapter 1: Introduction to Chemistry

Ch. 1: Introduction to
Chemistry
Standards: INQB; Matter consists of atoms that
have internal structures that dictate their
chemical and physical behavior.
Targets:
• What is Chemistry?
• Branches of Chemistry
• Areas Involving Chemistry
• Careers in Chemistry
• Scientific Method
What is Chemistry?
Chemistry is the study of the composition of
matter and the changes that matter undergoes.
• What is matter?
– Anything that takes up space and has mass
• What is change?
– Make into a different form
Branches of Chemistry
• Inorganic chemistry: Studies matter that
does not contain carbon
• Organic chemistry: Studies carboncontaining substances
• Analytical chemistry: Concerned with the
composition of substances
• Physical chemistry: Explains and
measures the behavior of substances
• Biochemistry: The chemistry of living
organisms
Areas of Our Society
Involving Chemistry
– Energy: Fuels, insulation, lighting, batteries,
nuclear
– Medicine and Biotechnology:
Pharmaceuticals, materials, genetics, cloning
– Agriculture: Fertilizer, pesticide, herbicides,
fungicides, new crops hormones
– Environment: Waste
reduction/treatment/disposal, chemical
management, monitoring
– Astronomy/Space Exploration: Rocket fuels,
compositions of moon, stars, and planets
– Materials: Metal alloys, plastics, coatings,
semiconductors
Careers in Chemistry
• Chemist: Analytical chemist, forensic chemist, solid state chemist,
organic chemist, biochemist, electrochemist, quality control
• Chemical Engineer: Process engineer, instrumentation and control
engineer, project engineer
• Materials Scientist: Metallurgist, polymer science, corrosion engineer
• Environmental Engineer: Ecologist, compliance, enforcement, waste
management, pollution abatement, remediation, HazMat response,
wastewater treatment
• Engineering: Mechanical, Civil, Ceramics, Nuclear
• Medical: Physician, nurse, lab technician, oncologist, veterinarian,
research
• Pharmacist: Retail, sales, research
Careers in Chemistry (cont.)
• Climatologist: Atmospheric scientist, computer modeling
• Oceanographer: Physical, chemical, geological, biological
• Solar Engineer: Photovoltaic cells, energy storage
• Commercial Diver: Underwater construction, welding, demolition,
exploration
• Laser Technician: Medical laser specialist, industrial laser
technician,
• Archeologist: Radioisotope dating, material identification
• Health Inspector: FDA, USDA, public health
• Microbiologist: Public health, medical, food, brewmaster, vintner
• Gemologist: Jewelers, insurance, mining
• Firefighter: Hazardous material response, emergency medical technician
Scientific Method
Steps of the Scientific Method:
1. Observation: Use your senses to obtain information
directly.
2. Problem: Propose a question based on your
observations
3. Hypothesis: Propose an explanation of your problem
(If…, then… statement)
4. Experiment: Test your hypothesis.
5. Results: collection of experiment’s data and analysis of
data
6. Conclusion: statements about what your experiment
found
Scientific Method
Important Terms:
o Theory: A broad and extensively tested
explanation of why experiments give certain
results.
o Ex: Atomic Theory: how the atom is structured
o Scientific Law: A concise statement that
summarizes the results of many observations
and experiments. A scientific law describes a
natural phenomenon without attempting to
explain it.
o Ex: Newton’s Laws of Motion
Types of Observations
Quantitative
• Must have numbers
involved
• Usually a
measurement using
metric units
Qualitative
• Using senses: color,
smell, texture
• NEVER TASTE
Accuracy and Precision
• Accuracy: the measure of how close a
measurement is to the actual or true value
• Precision: the measure of how close a
series of measurements are to one
another
Accuracy and Precision
Low accuracy
, Low
precision
Low accuracy,
High precision
Extensionengine.com
High
accuracy,
Low
precision
High
accuracy,
High
precision
Calculating Error
• Error: the difference between the accepted
value and the experimental value
– Accepted value: the correct value based on
reliable resources
– Experimental value: value measured in the lab
Error = experimental value - accepted value
Calculating Percent Error
• Percent Error: the relative error, shows
the magnitude of the error
Percent Error = I error I
x 100
accepted value
Measurement in Chemistry
• Use the International System of Units (SI)
– Aka: the metric system
Quantity
Unit
Symbol
Length
meter
m
Volume
Liter
L
Mass
gram
g
Temperature
Degree Celsius
oC
Density
Grams per cubiccentimeter or
Grams per mililiter
g/cm3 g/mL
Measurement in Chemistry
Devices to use for taking measurements:
– Balance – mass, usually in grams
– Ruler – length, usually in cm or mm
– Thermometer: temperature, usually in oC
– Graduated cylinder: volume, usually in mL
Measurement in Chemistry
Significant Figures (Sig Figs)
In science, a measured quantity has two
meanings:
 The numerical value (with the proper units)
 The sensitivity (uncertainty) of the measuring
instrument: precision
The number of sig figs is important in
calculations
Rules for Sig Figs
Rules for Counting Sig Figs
1. Every nonzero digit represented in a
measurement is significant.
24.7 m has 3 sig figs
0.4587 has 4 sig figs
134.798 has ? sig figs
0.6668 has ? sig figs
Rules for Sig Figs
2. Zeros appearing between non zero
digits are significant.
7003 has 4 sig figs
0. 96501 has 5 sig figs
40.30609 has ? sig figs
0.306201 has ? sig figs
Rules for Sig Figs
3. Zeros ending a number to the right of the
decimal point are significant
23.80 has 4 sig figs
0.130700 has 6 sig figs
1,006.00 has ? sig figs
0.34090 has ? sig figs
Rules for Sig Figs
4. Zeros starting a number or ending the
number to the left of the decimal point
are not counted as significant
16000 has 2 sig figs
0.0002709 has 4 sig figs
870,600 has ? sig figs
0.0450 has ? sig figs
Rules for Sig Figs
General Rule for Counting Sig Figs
Start on the left with the first nonzero digit.
End with the last nonzero digit OR with the last zero that
ends the number to the right of the decimal point
Sig Fig Practice
Indicate the number of sig figs in the numbers:
1.
2.
3.
4.
5.
5.678 m
0.0135 g
100.050 g
10.050 g
400.00 m
Rules for Sig Fig Calcuations
Sig Figs in Calculations: Addition &
Subtraction
•
The answer to an addition or subtraction
calculation must be rounded to the same
number of decimal places as the
measurement with the least number of
decimal places.
Rules for Sig Fig Calculations
12.52 m + 349.0 m + 8.24 m = 369.76 m
12.52 has 2 decimal places; 349.0 has 1
decimal place; 8.24 has 2 decimal places
The answer is rounded off to 1 decimal
place = 369.8 m
Rules for Sig Fig Calculations
Sig Figs in Calculations: Multiplication &
Division
 The answer to a multiplication or division
calculation must be rounded to the same
number of significant figures as the
measurement with the least number of
significant figures.
Sig Fig Practice
Metrics
Density
• The ratio of the mass of an object to its
volume
• Density = Mass
Volume