Introduction to Chemistry

The Chemical World

• Chemistry seeks to comprehend the behavior of matter by studying atoms and molecules.
• Chemicals are the building blocks of virtually everything.

Chemicals

• Chemicals aren't just dangerous poisons or pollutants, this is often a misconception
• Chemicals are present in the air, water, toothpaste, Tylenol, and toilet paper.

Atoms and Molecules in Matter

• Atoms are exceptionally minute and collectively form all matter.
• Atoms are bound together creating molecules.
• Chemical bonds connect atoms.

Molecular Models

• Atoms are represented by colored balls linked by sticks in the ball-and-stick model.
• Red represents Oxygen
• White represents Hydrogen
• Black represents Carbon
• Blue represents Nitrogen
• Yellow represents Sulfur

Water molecule

• Water molecules contain one oxygen and two hydrogen atoms that create a bent shape.
• These characteristics makes water a liquid at room temperature.

The Scientific Method

• Chemists use the scientific method, which emphasizes observation and experimentation to understand the world.
• Knowledge is obtained through senses.
• This method stands in contrast to ancient Greek philosophies and medieval applications.
• Those applications were based on reason to produce knowledge.

Observations

• Observations involve measuring or observing some aspect of nature.
• Some may require sensitive instrumentation beyond what can be seen with the naked eye.

Hypotheses

• Hypotheses are tentative interpretations of the observations.

Laws

• Laws summarize the results of a large number of observations.

Theories

• Theories are models that explain and give the underlying causes for observations and laws.

Experiments

• Hypotheses, laws, and theories must be tested and validated by experiment.
• Hypotheses that are not confirmed must be revised and tested through experimentation.

Antoine Lavoisier

• Antoine Lavoisier (1743–1794), a French chemist, made an observation about the physical world regarding combustion.
• Lavoisier measured mass in the process of combustion, which is burning.
• Mass measures the quantity of matter within an object.
• Lavoisier burned substances in closed containers while measuring the mass before and after burning.
• He observed no change in mass during combustion.

Hypothesis Testing

• Observations lead scientists to create hypotheses, which are tentative interpretations or explanations.
• A good hypothesis is falsifiable.
• Hypotheses are tested through experiments, which are controlled observations designed to validate or invalidate them.
• The results of experiments confirm or disprove hypotheses.
• Hypotheses may need modification or replacement based on the results of experiments.
• New or revised hypotheses require further testing through experimentation.

Law of Conservation of Mass

• A number of similar observations can lead to a scientific law.
• A scientific law is a statement that synthesizes past observations and predicts future ones.
• Lavoisier developed the law of conservation of mass.
• In a chemical reaction, matter is neither created nor destroyed, according to the law of conservation of mass.

The Scientific Method: Scientific Theory

• Well-established hypotheses can form the basis for a scientific theory.
• Theories provide a deeper description for observations and laws.
• Theories also model the way nature is.
• Theories can often predict behavior that goes beyond the observations and laws on which they are founded.

The Scientific Method: Experiments

• If a law, hypothesis, or theory is inconsistent with experimental findings, then revisions are required.
• Good theories remain and are consistent with experiments.

Established Theories

• Well-supported theories are the most powerful pieces of scientific knowledge.
• "That is just a theory," should not be said, as if they were mere speculations.
• Well-tested theories are as close to truth as science can deliver.

The Scientific Method: Atomic Theory

• The idea that matter is made of atoms is a 200-year-old theory.
• Modern technology provides images of atoms themselves to further prove this.

Chemistry Requires Calculation

• Quantification is measurement as part of observation.
• Quantification allows to specify the difference precisely.
• For example, two samples of water may feel equally hot, but one may measure 40°C, while the other measures 44°C.