Chemistry: The Study of Matter

Chemistry: The Study of Matter

• Chemistry is the study of the composition, structure, properties, and reactions of matter.
• Matter is anything that has mass and occupies space.

Six Major Areas of Chemistry

• Analytical Chemistry: Focuses on the composition of substances.
• Inorganic Chemistry: Primarily deals with substances that do not contain carbon.
• Organic Chemistry: Focuses on substances that contain carbon.
• Biochemistry: Studies the chemistry of living things.
• Physical Chemistry: Describes the behavior of chemicals, often using mathematics.
• Nuclear Chemistry: Deals with radioactivity, nuclear processes, and properties.

Pure vs. Applied Chemistry

• Pure Chemistry: Gathers knowledge for the sake of knowledge.
• Applied Chemistry: Utilizes chemistry to achieve specific goals in fields like medicine, agriculture, and manufacturing.

Chemistry in Everyday Life

• Chemists create materials for particular needs, such as Velcro (patented in 1955).
• Medicine and Biotechnology: Supply materials for healthcare, including vitamins, antibiotics, and materials for organ transplants.
• Energy: Chemistry plays a role in energy conservation and production, such as using soybeans to create biodiesel fuel.
• Agriculture: Chemistry is crucial for improving agricultural productivity, including soil management, pest control, and plant growth hormones.
• The Environment: Chemistry addresses the risks and benefits of scientific discoveries, including identifying and preventing pollutants.
• The Universe: Chemistry helps us study the composition of planets and analyze matter brought back to Earth.

The Origins of Chemistry

• The word "chemistry" comes from "alchemy," practiced in China and India since 400 B.C.
• Alchemy had two sides:
  • Practical: Techniques for working with metals.
  • Mystical: Concepts like perfection, where gold was considered the perfect metal.
• In the 1500s, a shift began from alchemy to science, supported by individuals like King Charles II and organizations like the Royal Society of London.

The Scientific Method

• A logical approach to solving problems or answering questions.
• Steps in the Scientific Method:
  • Observations: Using senses to gather information.
    • Quantitative: Involves numbers (e.g., 95°F).
    • Qualitative: Involves word descriptions (e.g., hot).
  • Formulating Hypotheses: Possible explanations or educated guesses.
  • Performing Experiments: Gathering new information to determine the validity of a hypothesis.

Variables in Experiments

• Manipulated Variable (Independent Variable): The factor that is changed.
• Responding Variable (Dependent Variable): The factor that is observed or measured.

Outcomes Over the Long Term

• Theory (Model): A well-tested set of hypotheses that offers an overall explanation of a phenomenon.
• Natural Law (or Scientific Law): Summarizes observations that apply to many different systems.

Distinguishing Laws and Theories

• Law: Summarizes what happened.
• Theory: Explains why it happened, and can change as new information is gathered.

CHAPTER II: Measurement and Estimation

• Estimation: Using knowledge of similar objects to determine the size or amount of a new object.
• Precision: How close measurements are to each other.
• Accuracy: How close a measurement is to the actual or accepted value.
• Measurement Systems:
  • English (Standard) System: Used in the United States.
  • Metric (SI) System: Used globally.

Basic Types of Measurement

• Length: Measures distance between objects.
• Mass: Measures the amount of matter in an object.
• Volume: Measures the amount of space an object occupies.
• Temperature: Measures the kinetic energy of atoms in an object.

CHAPTER III: Matter and Its Properties

• Matter: Anything that has mass and volume.
• Mass: The amount of matter in an object.
• Weight: The pull of gravity on an object
• Volume: The space an object occupies.
• Composition: What matter is made of.
• Properties: Describe the characteristics of matter, including appearance, smell, and behavior.

Atoms and Elements

• Atom: The basic building block of matter.
• Element: Contains only one type of atom.
  • Monatomic Elements: Consist of unbonded, identical atoms.
  • Polyatomic Elements: Consist of several identical atoms bonded together.
  • Diatomic Elements: Examples include H2, O2, Br2, F2, I2, N2, and Cl2. Remember the mnemonic "HOBrFINCl = Hoberfinckle."
• Allotropes: Different forms of the same element in the same state of matter.

Compounds

• Contain two or more different types of atoms.
• Have properties that differ from their constituent elements.

Classifying Matter

• Substances: Have fixed composition and properties.
• Mixtures: Two or more substances mixed together, with varying composition and properties.
  • Two Types of Mixtures:
    • Homogeneous: (or solution) Particles are microscopic; uniform composition and properties throughout.
    • Heterogeneous: Different composition and properties throughout the sample.

Separating Mixtures

• Involves physical means or physical changes.
• Methods for Separating Mixtures:
  • Sorting: By color, shape, texture, etc.
  • Filtration: Based on particle size differences.
  • Magnetism: One substance must contain iron.
  • Chromatography: Exploits differences in solubility.
  • Density: "Sink vs. float," utilizing a centrifuge if necessary.
  • Distillation: Based on different boiling points.
  • No chemical reactions are required to separate mixtures; substances are not bonded.

Properties of Matter

• Chemical Properties: Describe how a substance reacts with other substances.
• Physical Properties: Observable without altering the substance chemically.
• Extensive Properties: Depend on the quantity of substance present.
• Intensive Properties: Do not depend on the quantity of substance present.

Physical and Chemical Changes

• Physical Change: The formation of a mixture.
• Chemical Change: The formation of a compound.

Energy Changes

• Endothermic Change: The system absorbs heat.
• Exothermic Change: The system releases heat.

CHAPTER IV: Atomic Structure

• Democritus (460 B.C. -- 370 B.C.) - First to suggest the existence of atoms (from the Greek word "atomos"), believing they were indivisible and indestructible.

Dalton's Atomic Theory

• John Dalton (1766 -- 1844) Proposed a theory based on experimentation:
  • Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
  • In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.
  • All elements are composed of tiny indivisible particles called atoms.
  • Atoms of the same element are identical.
  • Atoms of any one element are different from those of any other element.

Discovery of the Electron

• In 1897, J.J. Thomson: Used a cathode ray tube to deduce the presence of a negatively charged particle: the electron.
  • Cathode Ray Tubes: Pass electricity through a gas at low pressure.
• 1916 -- Robert Millikan: Determined the mass of the electron as 1/1840 the mass of a hydrogen atom, with one unit of negative charge.

Conclusions from the Study of the Electron

• All elements contain identically charged electrons.
• Atoms are neutral, so they must contain positive particles to balance the negative charge of electrons.
• Electrons have so little mass that atoms must contain other particles that account for most of the mass.

Protons and Neutrons

• Eugen Goldstein in 1886: Observed the "proton" - a positively charged particle with a relative mass of 1 (or 1840 times that of an electron).
• 1932 -- James Chadwick: Confirmed the existence of the "neutron" - a neutral particle with a mass nearly equal to a proton.