Chemistry
111 concepts · 5 topics · K–12
Big questions chemistry answers
- What is this substance made of, and how are the atoms arranged?
- Is this a physical change or a chemical change?
- What atoms went in, and what atoms came out — does it balance?
- How much of A reacts with how much of B?
- Does the reaction finish, or does it sit at equilibrium?
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How the topics connect
Every chemistry family on one map. Lines show shared prerequisites.
Explore by Topic
Structure of Matter
Atoms, elements, compounds, bonding, molecular structure
35 conceptsChemical Change
Reactions, equilibrium, kinetics, thermochemistry
29 conceptsQuantity & Proportion
Moles, stoichiometry, concentration, gas laws
23 conceptsMatter & Mixtures
States of matter, properties, mixtures, separation
14 conceptsReaction Patterns
Synthesis, decomposition, displacement, combustion
10 conceptsBrowse by Grade Band
Chemistry starts with matter and materials, then builds toward atoms, reactions, and quantitative models.
Early ideas about matter, materials, and observable changes.
States of matter, mixtures, and physical properties in concrete contexts.
Atoms, periodic table basics, reactions, density, and conservation of mass.
High school chemistry including stoichiometry, gases, bonding, equilibrium, and electrochemistry.
Popular Concepts
Atom
The smallest unit of an element that retains the chemical properties of that element.
Periodic Table
A systematic arrangement of all known chemical elements organized by increasing atomic number into rows (periods) and columns (groups), where elements in the same group share similar chemical properties because they have the same number of valence electrons.
Chemical Bond
A lasting force of attraction between atoms that holds them together in molecules, compounds, or crystal lattices, formed when atoms share electrons (covalent bond), transfer electrons (ionic bond), or pool electrons (metallic bond).
Mole
The fundamental counting unit in chemistry, defined as exactly $6.022 \times 10^{23}$ particles (atoms, molecules, ions, or other entities).
Molar Mass
The mass in grams of exactly one mole of a substance, calculated by summing the atomic masses of all atoms in the chemical formula.
Stoichiometry
The branch of chemistry that uses balanced chemical equations and mole ratios to calculate the precise quantities of reactants consumed and products formed in chemical.
Gas Laws
A set of mathematical relationships that describe how the pressure, volume, temperature, and amount (moles) of a gas are interconnected.
Acid
A substance that donates $\text{H}^+$ ions (protons) when dissolved in water, increasing the hydrogen ion concentration and lowering the pH below 7.
Base
A substance that accepts $\text{H}^+$ ions (protons) or donates $\text{OH}^-$ ions when dissolved in solution, raising the pH above 7.
pH
A logarithmic scale (typically 0 to 14) that quantifies the hydrogen ion concentration $[\text{H}^+]$ in an aqueous solution: at 25°C, values below 7 are acidic, 7 is neutral, and above 7 is basic.
Chemical Equilibrium
A dynamic state in a reversible reaction where the forward and reverse reactions proceed at equal rates, so the macroscopic concentrations of reactants and products.
Electrochemistry
Electrochemistry is the study of redox reactions that involve electric current, either producing electricity from a spontaneous reaction (a galvanic/voltaic cell) or using electricity to force a nonspontaneous reaction to occur (an electrolytic cell).
Chemistry Guides
Priority guides and concept pages that go beyond short definitions with formulas, examples, FAQs, common mistakes, and stronger chemistry-to-chemistry links.
Chemistry Terms and Definitions
Core chemistry vocabulary like reactant, product, molecule, solution, acid, and base explained clearly.
Moles, Formulas, and Concentration
A connected guide to moles, molar mass, molecular formulas, and concentration calculations.
Mole
Definition, formula links, examples, FAQs, and common mistakes for chemistry’s counting unit.
Molar Mass
How to calculate molar mass, when to use it, and how it connects grams to moles.
Stoichiometry
Balanced-equation ratios, worked examples, and the mistakes students make when they skip the mole step.
pH
Clear pH definition, formula, examples, and acid-base connections for solution chemistry.
Features
Clear First Explanations
Every chemistry page starts with a direct definition before formulas, symbols, and formal language.
Connected Chemistry Links
Chemistry pages now link more strongly to related chemistry ideas like gas laws, equilibrium, stoichiometry, and acids-bases.
Interactive Playground
Visual models help you build intuition for atoms, bonding, reactions, pH, and solution chemistry.
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