Honors Chemistry Unit 1 Review: Introduction to Chemistry

Key Concepts and Definitions

• Matter consists of atoms which are the building blocks of all substances
• Elements are pure substances made up of only one type of atom and cannot be broken down into simpler substances by chemical means
• Compounds are substances composed of two or more elements chemically combined in a specific ratio
• Mixtures contain two or more substances that are not chemically combined and can be separated by physical means
  • Homogeneous mixtures have a uniform composition throughout (solutions)
  • Heterogeneous mixtures have a non-uniform composition (suspensions, colloids)
• Chemical properties describe how a substance behaves during a chemical reaction (reactivity, flammability)
• Physical properties can be observed or measured without changing the substance's composition (color, melting point, density)
• Chemical changes involve the formation of new substances with different properties than the original substances (rusting, combustion)
• Physical changes do not alter the chemical composition of a substance (melting, freezing, dissolving)

Atomic Structure and the Periodic Table

• Atoms consist of protons, neutrons, and electrons
  • Protons have a positive charge and are located in the nucleus
  • Neutrons have no charge and are also located in the nucleus
  • Electrons have a negative charge and orbit the nucleus in energy levels or shells
• The atomic number of an element is equal to the number of protons in its nucleus
• Isotopes are atoms of the same element with different numbers of neutrons
• The periodic table organizes elements based on their atomic number and chemical properties
  • Elements in the same group (column) have similar chemical properties
  • Elements in the same period (row) have the same number of electron shells
• Metals are located on the left side of the periodic table and are good conductors of heat and electricity
• Nonmetals are located on the right side of the periodic table and are generally poor conductors
• Metalloids have properties of both metals and nonmetals and are located along the "staircase" line on the periodic table

Chemical Bonding Basics

• Chemical bonds form when atoms share or transfer electrons to achieve a more stable electronic configuration
• Ionic bonds involve the transfer of electrons from one atom to another, forming positively and negatively charged ions
  • Ionic compounds are typically formed between metals and nonmetals
  • Ionic compounds have high melting points and are good conductors of electricity when dissolved in water or molten
• Covalent bonds involve the sharing of electrons between atoms
  • Nonmetals typically form covalent bonds with other nonmetals
  • Covalent compounds have lower melting points and are generally poor conductors of electricity
• Metallic bonds occur between metal atoms and involve a sea of delocalized electrons
  • Metallic bonding gives metals their characteristic properties such as malleability, ductility, and good conductivity
• Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond
  • Atoms with higher electronegativity values tend to gain electrons, while those with lower values tend to lose electrons

Stoichiometry and Chemical Equations

• Stoichiometry is the study of the quantitative relationships between reactants and products in a chemical reaction
• Chemical equations represent the reactants, products, and their stoichiometric coefficients in a reaction
  • Reactants are written on the left side of the arrow, and products are written on the right side
  • Coefficients indicate the relative numbers of molecules or moles of each substance involved in the reaction
• Balanced chemical equations have equal numbers of each type of atom on both sides of the equation
• Mole ratios can be derived from the coefficients in a balanced chemical equation and used to calculate the amounts of reactants or products
• Limiting reactants determine the maximum amount of product that can be formed in a reaction
• Theoretical yield is the maximum amount of product that can be obtained based on the limiting reactant
• Percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage

States of Matter and Phase Changes

• Matter exists in three main states: solid, liquid, and gas
  • Solids have a definite shape and volume and have particles that are closely packed and vibrate in fixed positions
  • Liquids have a definite volume but take the shape of their container and have particles that are close together but can move past each other
  • Gases have no definite shape or volume and have particles that are far apart and move randomly
• Phase changes occur when a substance transitions between states of matter
  • Melting is the change from a solid to a liquid
  • Freezing is the change from a liquid to a solid
  • Vaporization is the change from a liquid to a gas (evaporation, boiling)
  • Condensation is the change from a gas to a liquid
  • Sublimation is the change from a solid directly to a gas
  • Deposition is the change from a gas directly to a solid
• Energy is required to overcome intermolecular forces during phase changes that involve an increase in particle motion (melting, vaporization, sublimation)
• Energy is released during phase changes that involve a decrease in particle motion (freezing, condensation, deposition)

Introduction to Chemical Reactions

• Chemical reactions involve the breaking and forming of chemical bonds, resulting in the formation of new substances
• Reactants are the starting materials in a chemical reaction, while products are the substances formed as a result of the reaction
• Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process
• Endothermic reactions absorb energy from the surroundings, causing a decrease in temperature
• Exothermic reactions release energy to the surroundings, causing an increase in temperature
• Activation energy is the minimum energy required for a chemical reaction to occur
  • Catalysts lower the activation energy, allowing reactions to occur more quickly
• Reaction rates depend on factors such as temperature, concentration, surface area, and the presence of catalysts
  • Increasing temperature, concentration, or surface area generally increases the reaction rate
• Chemical equilibrium is a dynamic state in which the rates of the forward and reverse reactions are equal
  • Le Chatelier's principle states that a system in equilibrium will respond to a stress by shifting to counteract the stress and re-establish equilibrium

Lab Safety and Basic Techniques

• Always wear appropriate personal protective equipment (PPE) such as goggles, lab coats, and gloves
• Familiarize yourself with the location and use of safety equipment (eyewash stations, fire extinguishers, safety showers)
• Never eat, drink, smoke, or apply cosmetics in the lab
• Tie back long hair and avoid wearing loose clothing or dangling jewelry
• Handle chemicals and equipment with caution, and never taste or smell chemicals directly
• Use a fume hood when working with volatile or hazardous substances
• Properly dispose of chemical waste according to the lab's guidelines
• Basic lab techniques include:
  • Measuring mass using a balance
  • Measuring volume using graduated cylinders, pipettes, and burettes
  • Preparing solutions of specific concentrations
  • Heating substances using a Bunsen burner or hot plate
  • Filtering mixtures using gravity or vacuum filtration
  • Conducting titrations to determine the concentration of an unknown solution
• Always clean your work area and equipment after use and wash your hands before leaving the lab

Real-World Applications and Examples

• Batteries use redox reactions to convert chemical energy into electrical energy (lithium-ion batteries in smartphones)
• Catalytic converters in automobiles use catalysts to convert harmful pollutants into less harmful substances
• Photosynthesis is an endothermic reaction that converts light energy into chemical energy stored in glucose
• Combustion reactions are exothermic and are used to generate heat and power (burning fossil fuels for electricity)
• Electroplating involves the deposition of a thin layer of metal onto another surface using electrolysis (chrome-plated car parts)
• Pharmaceuticals are developed using principles of organic chemistry and chemical synthesis (aspirin, antibiotics)
• Fermentation is a metabolic process that produces ethanol and is used in the production of beer, wine, and bread
• Water treatment facilities use chemical processes to purify water for human consumption (chlorination, flocculation)