Chemistry is involved in fertilizers, fuels, catalytic converters, birth control, and screens.
Scientific Method
The scientific method emphasizes observation and experimentation.
It contrasts with ancient philosophers who relied on reason.
Steps:
Observation: Observing something (e.g., the sky is blue).
Hypothesis: Formulating a testable explanation (e.g., why is the sky blue?).
Experimentation: Testing the hypothesis.
Law/Theory: Forming a conclusion based on the results.
Process Details:
Start with an observation, come up with a hypothesis, test the hypothesis with an experiment.
If the experiment confirms the hypothesis, proceed; otherwise, revise the hypothesis.
Theories are a more advanced form of a law.
Antoine Lavoisier (Important Scientist)
Studied combustion by burning substances in closed containers and carefully measuring the mass.
Observed that there was no change in mass during combustion.
Wife recorded his results and translated his works.
Hypothesis:
Combustion is the combination of a substance with a component of air.
A good hypothesis is falsifiable, meaning it can be proven wrong.
Experimentation:
Involves highly controlled observations to validate or invalidate the hypothesis.
Scientific Law
A brief statement that summarizes past observations and predicts future ones.
Lavoisier developed the law of conservation of mass: In a chemical reaction, matter is neither produced nor destroyed.
Scientific Theory
A well-established hypothesis can develop into a theory (also called a model).
A deeper and broader explanation of observations and laws.
Example: Atomic theory of John Dalton, which explains the law of conservation of mass by stating that all matter is composed of small, indestructible particles called atoms.
Definitions
Observation: Measurement of some aspect of nature.
Hypothesis: Interpretation or explanation of observations.
Law: Brief statement summarizing past observations.
Theory: Model for the way nature is and explains what nature does.
Analyzing and Interpreting Data
Data sets of measurements constitute scientific data.
The best scientists see patterns that others have missed.
Example Analysis
Analyzing a graph of atmospheric carbon dioxide versus time.
CO2 comes from cars (exhaust), factories, and breathing.
The Y-axis is not beginning at zero.
The rate of increase has intensified since about 1960.
Calculations on a graph
If the rate stayed consistent, what would be the carbon dioxide concentration in 2050?
If the average rate is 1.4 PPM, multiply that by forty years (2010 to 2050), which equals 56 PPM increase. Add that increased value to the carbon dioxide level in 2010 (March), where you get 4.5.
Keys to Succeeding in Chemistry
Require curiosity and imagination.
Chemistry requires calculation.
Requires commitment to stay on top of the work.
No special talent is required
Introduction to Chapter 2
Chapter 2 focuses on conversion factors.
Demonstration
Density experiment: Coke will sink, Diet Coke will float.
Diet Coke floats because of the artificial sweetener, which requires significantly less amount to sweeten.
Coke's high fructose corn syrup increases it's density.
Relating Density to the sinking and floating of Coke and Diet Coke
Losing a Large Order Due to Units
Scientists and engineers can make mistakes with units.
In 1998, NASA lost Mars Climate Orbiter (weather satellite) due to a unit mix-up.
The cost of the failed mission was estimated at $125,000,000.
The orbiter got within 57 kilometers of the planet's surface, which was too close, and disintegrated.
Onboard computers used metric units (Newton-seconds), but ground engineers used pound-seconds.
One pound-second is 4.45 Newton-seconds, a large difference.
Trajectory corrections were 4.4 times too small and did not keep the orbiter at a high enough altitude.
Scientific Notation
Used for writing very small and very large numbers.
A number between one and ten multiplied by 10 to an exponent.
1 \times 10^{-15} (small number).
1.4 \times 10^{10} (large number).
Steps:
Pick a number, move the decimal and have a number between one and ten.
If the exponent is positive, it's a big number; if negative, it's a small number.
Example:
The speed of light: 332,000,000 can be expressed as 3.32 \times 10^8.
Numbers and Precision
Significant figures reflect precision.
Scientific Notation Problems
The national debt was around 33 trillion dollars, and if expressed in scientific notions is 3.3 \times 10^{13}.
Accuracy and Precision in Measuring
Precision: How well several determinations of a quantity agree
Accuracy: How well a determination agrees with a true value
Significant Figures Digits
The more digits equals more precision.
Every number except for the last is certain. The last one's estimated.
Must be as precise as the measuring device.
Rules for counting Significant Figures
All non zero digits are significant.
Interior zeros are significant.
Trailing zeros are significant.
Trailing zeros occur after a decimal point are significant.
Leading zeros are not significant.
Significant Figures Calculation Examples
Ex) 0. 002 has one significant figure
Ex) 0. 00200 has 3 significant figures
Exact Numbers:
Unlimited number of significant figures that do not affect significant figures calculation.
Counting numbers (10 pencils; three atoms) are all significant.
Conversion factors, like, how many centimeters or in a meter, are unlimited for significant figures.
Interval numbers are part of the equation.
Like the radius is one half the diameter, which is considered unlimited for significant figures.
Significant Figures Practice Problems
0. Two
4. Four
One Dozen equal 12 (unlimited significant numbers)
Five because of the zero being recorded passed the decimal in addition to nonzero numbers.
Hundred thousand number with numbers with numbers that are zeros except after a the decimal DO not equate to unlimited significant figures.
Round down if the last or leftmost digit dropped is four or less.
Round up if last or leftmost digit is five or greater.
Multiple and Division Multiplication
Keep the same number of significant figures at the factor is the fewest.
There are two different rules for multiplication.
Practice Problem
Ex) 5.11 \times 4.2 = 0.2146 turns into 21 after rounding due to multiplying the smallest significant number.
Calculations
Addition and subtraction also the main reason can't see by the addition, the same the same number of decimal places and the one for the views.
Practice Problem: 24.335+8.1=32.4
Multistep Problems: Combining The Rules
(5.66 – 4.022) / 6.1=0.2685=0.27
Parentheses first, then do the multiplication and divide
Unit Conversions
Most problems in this book are unit conversion problems or equation problems.
Multiply, divide, and cancel units like algebraic expression.
Always write your notes and calculations, and don't let units appear and disappear because unit conversions are unit conversional
Understanding Conceptions With Unlimited Figures
Exact numbers, such as 2.54 centimeters per is unlimited.
*Conversion factor factor. Must have 1 inch =2.54 centimeters with it centimeters, on the bottom
Multiple Factors
Given what you have,
multiply it by a factor or factors depending on if it has a long chain. 1 equals one so you can do whatever you want with them. I can't reach centimeters to inches. If I use the correct conversion factors, the units should cancel and create them correct final units, then you will need to find.