Intro to Chemistry Unit 1 Review: Essential Ideas

Key Concepts and Definitions

• Chemistry studies the composition, structure, properties, and reactions of matter, especially at the atomic and molecular level
• Matter anything that has mass and takes up space (volume)
• Element a pure substance that consists of only one type of atom and cannot be broken down into simpler substances by chemical means (oxygen, carbon, iron)
• Atom the smallest unit of an element that retains its chemical properties
  • Consists of a dense nucleus containing protons and neutrons surrounded by electrons in shells
• Molecule two or more atoms held together by chemical bonds (water, carbon dioxide)
• Compound a substance made up of two or more elements chemically combined in a fixed ratio (salt, sugar)
• Mixture a physical combination of two or more substances that can be separated by physical means (salt water, air)
• Physical change alters the form of a substance without changing its chemical composition (melting ice)
• Chemical change (reaction) a process that transforms one set of chemical substances into another, forming new substances with different properties

Atomic Structure and Properties

• Atoms consist of protons (positive charge), neutrons (no charge), and electrons (negative charge)
  • Protons and neutrons make up the dense nucleus at the center of the atom
  • Electrons orbit the nucleus in shells at fixed energy levels
• Atomic number the number of protons in an atom's nucleus, unique to each element
• Mass number the total number of protons and neutrons in an atom's nucleus
• Isotopes atoms of the same element with different numbers of neutrons (carbon-12, carbon-13, carbon-14)
  • Isotopes have the same chemical properties but different physical properties (radioactivity, stability)
• Periodic table organizes elements by increasing atomic number and groups them by similar properties
  • Periods (rows) elements with the same number of electron shells
  • Groups (columns) elements with the same number of valence electrons and similar chemical properties
• Valence electrons outermost electrons involved in chemical bonding and reactions
• Electronegativity the ability of an atom to attract electrons in a chemical bond (fluorine, oxygen)

Chemical Bonding Basics

• Chemical bond an attractive force that holds atoms together in molecules or compounds
• Ionic bond formed by the electrostatic attraction between oppositely charged ions (sodium chloride)
  • Involves the transfer of electrons from a metal to a nonmetal
  • Creates crystalline solids with high melting points and electrical conductivity when dissolved or molten
• Covalent bond formed by the sharing of electrons between two nonmetals (water, methane)
  • Electrons are shared equally in nonpolar covalent bonds (oxygen gas)
  • Electrons are shared unequally in polar covalent bonds due to electronegativity differences (water)
• Metallic bond formed by the attraction between positively charged metal ions and delocalized electrons (copper, aluminum)
  • Accounts for the malleability, ductility, and thermal and electrical conductivity of metals
• Intermolecular forces weak attractions between molecules (hydrogen bonding, dipole-dipole, London dispersion)
  • Influence physical properties like boiling point, viscosity, and surface tension
• Lewis structures diagrams that show the bonding and lone pair electrons in molecules using dot notation (water, ammonia)

Matter and Energy

• States of matter solid, liquid, gas, and plasma
  • Solids have a fixed shape and volume (ice)
  • Liquids have a fixed volume but take the shape of their container (water)
  • Gases have no fixed shape or volume and expand to fill their container (helium)
  • Plasma an ionized gas with free electrons and positive ions (stars, neon signs)
• Phase changes transitions between states of matter (melting, freezing, vaporization, condensation, sublimation, deposition)
  • Require the addition or removal of energy (heat)
• Thermochemistry the study of heat and energy changes in chemical reactions
• Endothermic reaction absorbs heat from the surroundings (melting ice, photosynthesis)
• Exothermic reaction releases heat to the surroundings (combustion, neutralization)
• Conservation of energy energy cannot be created or destroyed, only converted from one form to another
• Specific heat capacity the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius (water has a high specific heat capacity)

Chemical Reactions Overview

• Reactants the starting materials in a chemical reaction (hydrogen and oxygen in the formation of water)
• Products the substances formed as a result of a chemical reaction (water from the reaction of hydrogen and oxygen)
• Chemical equation a symbolic representation of a chemical reaction using chemical formulas and symbols (2H2 + O2 -> 2H2O)
  • Reactants are written on the left side of the arrow, products on the right
  • Coefficients indicate the relative amounts of each substance (2 molecules of hydrogen, 1 molecule of oxygen, 2 molecules of water)
• Law of conservation of mass matter is neither created nor destroyed in a chemical reaction, only rearranged
• Balancing equations adjusting coefficients to ensure the same number of atoms of each element on both sides of the equation
• Types of reactions synthesis (combination), decomposition, single displacement, double displacement, combustion
• Reaction rate the speed at which a chemical reaction occurs, influenced by factors like temperature, concentration, surface area, and catalysts
• Catalyst a substance that speeds up a reaction without being consumed (enzymes, transition metals)

Measurement and Units in Chemistry

• SI units (International System of Units) a standardized system of measurement used in science
  • Base units include the meter (length), kilogram (mass), second (time), kelvin (temperature), mole (amount of substance), ampere (electric current), and candela (luminous intensity)
• Derived units combinations of base units (volume in cubic meters, density in kilograms per cubic meter)
• Prefixes used to indicate multiples or fractions of base units (kilo-, centi-, milli-, micro-, nano-)
• Dimensional analysis a problem-solving method that uses the relationships between quantities and their units to convert from one unit to another
• Significant figures the number of digits in a measured value that are known with certainty plus one estimated digit
  • Used to indicate the precision of a measurement and to guide calculations
• Accuracy how close a measured value is to the true value
• Precision how close repeated measurements are to each other, regardless of accuracy

Lab Safety and Techniques

• Personal protective equipment (PPE) items worn to minimize exposure to hazards (safety goggles, lab coats, gloves)
• Fume hood a ventilated enclosure used to conduct experiments with hazardous or volatile substances
• Fire safety equipment fire extinguishers, fire blankets, and safety showers
  • Different types of fire extinguishers for different classes of fires (water, foam, dry chemical, carbon dioxide)
• Chemical storage and labeling guidelines for the proper storage and identification of chemicals in the lab (flammables, corrosives, oxidizers)
• Material Safety Data Sheets (MSDS) documents that provide information on the properties and hazards of chemicals
• Basic lab techniques measuring volume (graduated cylinders, pipettes), measuring mass (balances), heating substances (Bunsen burners, hot plates), filtering mixtures (gravity filtration, vacuum filtration)
• Titration a technique used to determine the concentration of an unknown solution by reacting it with a solution of known concentration (acid-base titrations)
• Spectroscopy techniques that use the interaction of matter and electromagnetic radiation to identify and quantify substances (UV-Vis, IR, NMR)

Real-World Applications

• Pharmaceuticals the development and production of drugs to treat diseases and medical conditions
  • Involves the synthesis, purification, and testing of active ingredients and formulations
• Materials science the study of the structure, properties, and performance of materials (metals, ceramics, polymers, composites)
  • Aims to develop new materials with improved or tailored properties for specific applications (lightweight alloys for aerospace, biodegradable plastics)
• Environmental chemistry the study of chemical processes in the environment and the impact of human activities
  • Includes topics like air and water pollution, climate change, and waste management
• Forensic chemistry the application of chemistry to criminal investigations and legal proceedings
  • Involves the analysis of evidence like drugs, explosives, and bodily fluids to help solve crimes
• Food chemistry the study of the chemical composition, properties, and reactions of food components
  • Aims to improve food safety, quality, and shelf life through the development of new ingredients, processing methods, and packaging materials
• Energy and fuels the study of the production, storage, and use of energy from chemical sources (fossil fuels, biofuels, batteries)
  • Focuses on developing cleaner and more efficient energy technologies to reduce environmental impact
• Nanotechnology the manipulation of matter at the nanoscale (1-100 nanometers) to create materials and devices with unique properties
  • Applications include targeted drug delivery, water purification, and high-strength composites