Introduction to Chemistry: Matter and Composition

• Chemistry is the study of matter, its properties, and how it changes

Matter

• Matter has mass and occupies space (volume)
• Matter exists as solids, liquids, gases, and plasma
• Solids possess a definite shape and volume
• Liquids have a definite volume but assume the shape of their container
• Gases lack a definite shape or volume and are compressible
• Plasma constitutes an ionized gas at high temperatures

Elements and Compounds

• An element is a pure substance that consists of only one type of atom and cannot be broken down via chemical means
• A compound consists of two or more elements chemically bonded
• Compounds exhibit different properties than their constituent elements

Atoms and Molecules

• An atom is the fundamental unit of matter that retains an element's chemical properties
• Atoms consist of protons, neutrons, and electrons
• Protons, located in the nucleus, carry a positive charge
• Neutrons, also in the nucleus, have no charge
• Electrons, which have a negative charge, orbit the nucleus in electron shells
• A molecule comprises two or more atoms held together by chemical bonds
• Molecules can be elements (e.g., O2) or compounds (e.g., H2O)

Chemical Bonds

• A chemical bond is an attractive force between atoms enabling the formation of chemical substances
• Ionic bonds arise from electron transfer between atoms, resulting in ions
• Covalent bonds involve the sharing of electrons between atoms
• Metallic bonds occur in metals where electrons are delocalized and shared among many atoms

Chemical Reactions

• A chemical reaction is a process involving the rearrangement of atoms and molecules to produce new substances
• Chemical equations utilize chemical formulas and symbols to represent chemical reactions
• Balancing chemical equations ensures an equal number of atoms for each element on both sides
• Types of chemical reactions include synthesis, decomposition, single replacement, and double replacement

Stoichiometry

• Stoichiometry involves the quantitative relationships between reactants and products in chemical reactions
• The mole is the SI unit denoting the amount of a substance
• Molar mass is the mass of one mole of a substance
• Stoichiometric calculations facilitate the prediction of reactant and product amounts in a chemical reaction

Acids and Bases

• Acids donate protons (H+) or accept electrons
• Bases accept protons or donate electrons
• pH measures a solution's acidity or basicity
• Acids have a pH below 7, bases above 7, and neutral substances have a pH of 7
• Acid-base reactions involve proton transfer from an acid to a base, forming a salt and water

Solutions

• A solution is a homogeneous mixture of multiple substances
• A solute dissolves into a solvent
• Concentration measures the solute amount in a solvent or solution
• Molarity (M) expresses concentration as moles of solute per liter of solution
• Solubility is the maximum solute amount that can dissolve in a solvent at a specific temperature

Thermochemistry

• Thermochemistry studies heat and energy concerning chemical reactions
• Energy is the capacity to perform work
• Heat involves the transfer of thermal energy between objects at varying temperatures
• Exothermic reactions release heat, while endothermic reactions absorb heat
• Enthalpy (H) measures heat changes at constant pressure
• Hess's Law asserts that the enthalpy change for a reaction remains independent of the pathway

Chemical Kinetics

• Chemical kinetics studies reaction rates and influencing factors
• Reaction rate signifies the change in reactant or product concentration per unit time
• Factors influencing reaction rates include temperature, concentration, surface area, and catalysts
• Catalysts accelerate reactions by reducing activation energy

Chemical Equilibrium

• Chemical equilibrium occurs when forward and reverse reaction rates equalize
• At equilibrium, reactant and product concentrations remain stable
• Le Chatelier's Principle states a system at equilibrium shifts to relieve stress from changed conditions
• Factors affecting equilibrium include concentration, temperature, and pressure

Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds
• Carbon atoms form stable bonds with each other, enabling many organic molecules
• Functional groups dictate the characteristic chemical reactions of molecules
• Common functional groups encompass alcohols, ethers, aldehydes, ketones, carboxylic acids, and amines
• Isomers share molecular formulas but differ in structural formulas

Biochemistry

• Biochemistry studies chemical processes in living organisms
• Key biomolecules encompass carbohydrates, lipids, proteins, and nucleic acids
• Carbohydrates provide energy and structural components
• Lipids, like fats, oils, and waxes, store energy and construct cell membranes
• Proteins catalyze reactions, transport molecules, and provide structural support
• Nucleic acids (DNA and RNA) carry genetic information