Introduction to Chemistry

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

Basic Concepts

• Matter has mass and takes up space
• Atoms are the basic building blocks of matter
• Elements consist of only one type of atom and cannot be broken down chemically
• Compounds consist of two or more different elements chemically bonded
• Molecules are the smallest units of a compound that retain its chemical properties
• Mixtures are combinations of two or more physically combined substances, not chemically bonded

States of Matter

• Solid: Definite shape and volume
• Liquid: Definite volume, shape conforms to its container
• Gas: No definite shape or volume
• Plasma: Ionized gas at high temperature

Chemical Reactions

• Chemical reactions rearrange atoms and molecules to form new substances
• Reactants are the starting materials
• Products are the formed substances
• Balancing chemical equations ensures the same number of atoms for each element on both sides, adhering to the law of conservation of mass

Stoichiometry

• Stoichiometry deals with quantitative relationships between reactants and products
• The mole is the SI unit for the amount of substance, defined as the number of atoms in exactly 12 grams of carbon-12 (Avogadro's number, approximately 6.022 x 10^23)
• Molar mass is the mass of one mole of a substance (g/mol)
• A limiting reactant is fully consumed, determining the maximum product amount
• Percent yield = (actual yield / theoretical yield) x 100

Acids and Bases

• Arrhenius: Acids produce H+ in water, bases produce OH- in water
• Bronsted-Lowry: Acids are proton (H+) donors, bases are proton acceptors
• Lewis: Acids are electron pair acceptors, bases are electron pair donors
• pH measures acidity or basicity; pH = -log[H+]
• Acid-base neutralization: Acids react with bases to form salts and water

Thermodynamics

• Thermodynamics studies energy and its transformations
• Energy is the capacity to do work
• First law: Energy is conserved, only converted in form
• Enthalpy (H) is the sum of internal energy and the product of pressure and volume; ΔH = qp (heat at constant pressure)
• Exothermic reactions release heat (ΔH < 0), endothermic absorb heat (ΔH > 0)
• Entropy (S) measures disorder or randomness
• Second law: Total entropy in an isolated system increases in spontaneous processes
• Gibbs free energy (G) combines enthalpy and entropy to determine reaction spontaneity; G = H - TS
• A reaction is spontaneous if ΔG < 0, at equilibrium if ΔG = 0, and non-spontaneous if ΔG > 0

Chemical Kinetics

• Chemical kinetics studies reaction rates and affecting factors
• Reaction rate is the change in concentration of reactants or products per unit time
• Rate law expresses the relationship between the rate of a reaction and the concentrations of the reactants; rate = k[A]^m[B]^n
• Reaction order is the sum of the exponents in the rate law (m + n)
• Activation energy (Ea) is the minimum energy for a reaction to occur
• Catalysts lower activation energy to speed up reactions

Electrochemistry

• Electrochemistry studies the relationship between electricity and chemical reactions
• Oxidation is the loss of electrons, reduction is the gain (redox reactions)
• Electrochemical cells convert chemical energy into electrical energy (galvanic cells) or electrical energy into chemical energy (electrolytic cells)
• Anode is the electrode where oxidation occurs
• Cathode is the electrode where reduction occurs
• Cell potential (Ecell) is the potential difference between the cathode and anode, measured in volts
• Nernst equation relates cell potential to standard cell potential and reactant/product concentrations

Coordination Chemistry

• Coordination complexes have a central metal ion surrounded by ligands
• Ligands donate electrons to the metal ion to form a coordinate covalent bond
• Coordination number is the number of ligands attached to the central metal ion
• Isomers have the same chemical formula but different atomic arrangements
• Crystal field theory explains electronic structure and properties of coordination complexes based on metal ion and ligand interaction

Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds
• Carbon forms single, double, and triple bonds with other carbon atoms and elements
• Hydrocarbons are made of only carbon and hydrogen
• Alkanes are saturated hydrocarbons with single bonds
• Alkenes are unsaturated hydrocarbons with one or more double bonds
• Alkynes are unsaturated hydrocarbons with one or more triple bonds
• Functional groups are specific groups of atoms within molecules with characteristic chemical reactions, i.e. alcohols, ethers, aldehydes, ketones, carboxylic acids, amines, amides, esters
• Isomers have the same molecular formula but different structural formulas or spatial arrangements

Spectroscopy

• Spectroscopy studies the interaction of electromagnetic radiation with matter
• UV-Vis spectroscopy studies UV and visible light absorption, used to determine substance concentration
• Infrared (IR) spectroscopy studies infrared radiation absorption, used to identify functional groups
• Nuclear magnetic resonance (NMR) spectroscopy studies radiofrequency radiation absorption by atomic nuclei in a magnetic field, used to determine molecular structure
• Mass spectrometry measures the mass-to-charge ratio of ions, used to determine molecular weight and structure

Explore the fundamental principles of chemistry, including the composition and properties of matter. Learn about atoms, elements, compounds, and mixtures. Discover the different states of matter: solid, liquid, gas, and plasma.