Practice to Mastery: U.S. High School Chemistry is a comprehensive practice and review workbook covering the complete U.S. high-school chemistry curriculum across 15 chapters and approximately 1,790 problems. Topics span the full range of high-school chemistry: matter and measurement; atomic structure and the periodic table; chemical bonding and molecular geometry; chemical formulas and nomenclature; gases and the gas laws; stoichiometry and the mole; liquids, solids, phase changes and solutions; chemical reactions and thermochemistry; reaction rates; chemical equilibrium; acids, bases and salts; oxidation-reduction and electrochemistry; representative groups and families; organic chemistry; and laboratory skills and practices. Each chapter follows the same five-part structure that builds from recall to application: Part A - Single-Answer Multiple Choice; Part B - Multiple-Select; Part C - Short Answer & Calculations; Part D - Scenario Applications; Part E - Laboratory & Experimental Skills. Every chapter opens with a "Topics Covered" list so students can identify gaps before they start, and every problem in the answer key carries a difficulty tag - Easy, Medium, or Hard - together with a complete, sentence-style worked explanation. Mathematical expressions use real fractions and radicals; chemical formulas use proper subscripts and superscripts; equations are balanced and marked with phase states (aq, g, l, s). To support efficient review, the back of the book opens each chapter's solutions with an Answer Key - Quick Reference - a compact table listing every multiple-choice and multi-select answer letter at a glance. Detailed step-by-step explanations follow immediately below, including notes on why each incorrect option is wrong, the relevant formulas or principles, and the broader concept being tested. Designed for students reviewing for unit tests, mid-terms and finals; for homeschoolers following a structured practice plan; for AP Chemistry candidates needing foundational review; and for teachers seeking a flexible question bank for homework, quizzes, and remediation. The workbook is not framed as preparation for any specific national examination, but its content fully aligns with the topics covered in essentially every U.S. high-school chemistry curriculum.