CHEM 1411 Chapter 1 Notes

1.1 Chemistry in Context

• Chemistry is the central science due to its interconnectedness with other STEM disciplines (Science, Technology, Engineering, and Math).

Branches of Chemistry

• Organic Chemistry: Study of carbon-containing compounds.
• Inorganic Chemistry: Study of non-carbon-containing compounds, including some small carbon-containing compounds like CO and CO_2.
• Biochemistry: Study of processes in living organisms.
• Analytical Chemistry:
  • Qualitative: What?
  • Quantitative: How much?
• Physical Chemistry: Study that proposes theoretical and mathematical explanations for chemical behavior.
• Green Chemistry: Design of chemical products and processes that reduce or eliminate hazardous substances.
• General Chemistry: Study of all the above branches.

The Scientific Method

• Chemistry is a science based on observation and experimentation.
• Chemists aim to answer questions and explain observations using existing laws and theories.
• Hypothesis: A tentative explanation for an observation, phenomenon, or scientific problem.
• Hypotheses are tested through experimentation, calculation, and/or comparison.

Steps of the Scientific Method

1. Observation
2. Hypothesis
3. Experiments
4. Collect Data
5. Analyze Data
6. Conclusion

Law vs. Theory

• Law:
  • Established after many experiments give the same observation.
  • Used to predict the occurrence of something in the natural world.
  • Describes behavior without explaining how or why.
• Theory:
  • An explanation of experiments or observations.
  • Can never be proven.
  • Future experiments may disprove a theory.
  • Evidence supports a theory.

1.2 Phases and Classification of Matter

• Matter: Anything that has mass and takes up space.
• Three common states of matter on Earth:
  • Solid: Rigid, definite shape and volume.
  • Liquid: Flows and takes the shape of a container.
  • Gas: No definite shape and takes the shape and volume of its container.

Plasma - 4th State of Matter

• Gaseous mixture of free electrons and cations (positively charged particles).
• Ionized gas.
• No definite shape or consistent volume.
• Flows easily and takes the shape of a container.
• Occurs naturally in the interiors of stars.

Mass vs. Weight

• Mass: A measure of the amount of matter.
• Weight: The force that gravity exerts on an object.
• Force is directly proportional to the mass of the object: F = ma
• Weight changes with the force of gravity, but mass does not.
• The moon's gravity is 1/6 of Earth's gravity, so your weight on the moon is 1/6 of your weight on Earth, but your mass stays the same.

Law of Conservation of Matter

• When matter converts from one type to another or changes phase, there is no change in the total amount of matter present.
• Matter can neither be created nor destroyed.

Classifying Matter

• Matter is classified as a pure substance or a mixture.
• Pure Substance: Has a constant composition and is comprised of only one type of element or molecule. Cannot be separated by physical means.
  • Element: A pure substance that cannot be broken down into a simpler substance by chemical changes (Periodic Table).
  • Compound: A pure substance that can be broken down by chemical changes, producing elements or other compounds.
    • Example: Heating mercury (II) oxide (HgO) breaks it down into mercury (Hg) and oxygen (O_2).
• Mixture: A combination of two or more substances, each retaining its own composition and properties. No chemical changes occur. Can be separated by physical means.
  • Heterogeneous Mixture: Composition varies from point to point. Composition is not uniform throughout.
    • Examples: Italian dressing, vegetable soup, iced tea with lemon.
  • Homogeneous Mixture: Has a uniform composition. Two or more substances combine and appear as one; also called a solution.
    • Examples: Vanilla pudding, tap water, nail polish remover, Gatorade, syrup, soda.

Classification of Matter Diagram

Matter?

• Does it have constant properties and composition?
  • No: Mixture
  • Yes: Pure substance
• Mixture
  • Is it uniform throughout?
    • No: Heterogeneous
    • Yes: Homogeneous
• Pure substance
  • Can it be simplified chemically?
    • No: Element
    • Yes: Compound

Matter Practice

• Copper: element
• Gasoline: homogeneous mixture
• NaCl: compound
• A cup of hot coffee: homogeneous mixture
• Granite: heterogeneous mixture
• CH_4: compound
• Dr. Pepper (flat): homogeneous mixture

Atoms and Molecules

• Atom: The smallest particle of an element that has the properties of that element and can enter into a chemical combination.
  • Examples: H, C, O
• Molecule: Two or more atoms joined by chemical bonds.
  • Examples: H2, CO, CO2, H_2CO

1.3 Physical and Chemical Properties

• Properties are characteristics that enable us to distinguish one substance from another; classified as physical or chemical.
• Physical Property: A characteristic of matter that is not associated with a change in its chemical composition.
  • Can be observed without changing the composition of the matter.
  • Examples: Odor, color, density, melting and boiling points, solubility, etc.
• Chemical Property: A characteristic of matter that is associated with a change in its chemical composition (or its inability to change).
  • Can only be determined by trying to change the composition of matter.
  • Examples: Flammability, toxicity, acidity, reactivity, oxidation.
    • The Statue of Liberty's copper skin changed color from brown to green due to chemical reactions: Copper oxidized to form Cu2O, then CuO, and further reacted to form Cu2CO3(OH)2 (green), Cu2(CO3)2(OH)2 (blue), and Cu4SO4(OH)_6 (green).
    • Fe oxidizes to form Fe2O3, while chromium does not oxidize.

Physical and Chemical Changes

• Physical Change: A change in the state or properties of matter without changing its chemical composition.
  • Examples: Phase changes, cutting paper, dissolving salt in water.
  • Many times, the original matter can be easily retrieved.
• Chemical Change: Produces one or more types of matter that differ from the starting matter.
  • Examples: Fe rusting to form Fe2O3, burning gasoline, cooking an egg, Cu oxidizing.

Indications of a Chemical Change

1. Color change
2. Gas is produced
3. Temperature change
4. New substance is formed
5. Odor released
   • Examples: Formation of rust, all forms of combustion (burning), and cooking/digesting/rotting food.

Physical and Chemical Properties Practice

• Color: physical property
• Density: physical property
• Flammability: chemical property
• Boiling Point: physical property
• Reactivity: chemical property
• Solubility: physical property

Physical and Chemical Changes Practice

• Ice melting: physical change
• Burning wood: chemical change
• Baking a cake: chemical change
• Food spoiling: chemical change
• Carving wood: physical change
• Forming liquid water by applying heat to an ice cube: physical change

Extensive and Intensive Properties

• Extensive Properties: Depend on the amount of matter present.
  • Examples: Mass, volume, heat.
• Intensive Properties: Do not depend on the amount of matter present.
  • Examples: Color, temperature.
• Intensive properties are independent of amount.

Extensive and Intensive Practice:

• Melting point: intensive
• Mass: extensive
• Color: intensive
• Volume: extensive
• Density: intensive

1.4 Measurements

• Every measurement provides three types of information:
  1. The magnitude of the measurement - Number
  2. A standard of comparison for the measurement - Unit
  3. An indication of the uncertainty (or error) of the measurement

Scientific Notation

• Measurements are written in decimal form or scientific notation.
• Atoms and molecules are very small; there are about 7,900,000,000,000,000,000,000,000 molecules of water in a glass.
• 7,900,000,000,000,000,000,000,000 can be written as 7.9 {x} 10^{24}.

Scientific Notation Example

• To write 4,300,000 in scientific notation:
  1. Place one nonzero digit to the left of the decimal point: 4.3
  2. Count how many digits the new decimal is from the original: 6
  • 4,300,000 = 4.3 {x} 10^6
    • 4. 3 is the number part.
    • 10^6 is the exponential part.

Scientific Notation: Moving the Decimal

• If you move the decimal point to the left, making the number part