Chemistry terms starting with P

Phenolphthalein Acids, Bases & Salts Dimensionless An acid–base indicator that is colourless in acid and pink in alkaline solution, changing between pH 8.3 and 10.0. C₂₀H₁₄O₄

Phospholipid Biochemistry & Polymer Chemistry Dimensionless A lipid in which one fatty acid of a triglyceride is replaced by a phosphate-containing group.

Photochemical Quantum Yield Chemical Kinetics & Catalysis Dimensionless The number of molecules reacting for each photon of light absorbed by the system. Φ = molecules reacted / photons absorbed

Photochemical Reaction Stoichiometry & Chemical Reactions nm A reaction initiated by the absorption of light, which promotes a molecule to an electronically excited state. A + hν → A*

Photosynthesis Biochemistry & Polymer Chemistry kJ/mol The process by which plants use light energy to convert carbon dioxide and water into carbohydrate and oxygen. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Physical Change Foundations of Chemistry Dimensionless A change that alters the form or state of a substance while leaving its chemical composition intact.

Physical Equilibrium Chemical Equilibrium Dimensionless An equilibrium between two physical states or phases of the same substance. H₂O(l) ⇌ H₂O(g)

Physical Property Foundations of Chemistry Various A characteristic of a substance that can be observed or measured without altering its chemical identity.

Physisorption Chemical Kinetics & Catalysis kJ/mol Weak adsorption in which molecules are held to a surface by van der Waals forces alone. ΔH ≈ −20 to −40 kJ/mol

Pi Bond Chemical Bonding & Molecular Structure kJ/mol A covalent bond formed by the sideways overlap of parallel p orbitals, with electron density above and below the internuclear axis.

pKa Acids, Bases & Salts Dimensionless The negative logarithm of the acid dissociation constant, giving a convenient scale of acid strength. pKa = −log Ka

pKb Acids, Bases & Salts Dimensionless The negative logarithm of the base dissociation constant. pKb = −log Kb

Plasma States of Matter & Gas Laws K A state of matter consisting of a hot, electrically conducting mixture of ions and free electrons.

Plum Pudding Model Atomic Structure & Periodicity Dimensionless J. J. Thomson's 1904 model picturing the atom as a sphere of diffuse positive charge with electrons embedded within it.

pOH Acids, Bases & Salts Dimensionless The negative logarithm of the hydroxide ion concentration. pOH = −log[OH⁻]; pH + pOH = 14

Polar Covalent Bond Chemical Bonding & Molecular Structure D A covalent bond in which the shared electrons are unequally distributed because the bonded atoms differ in electronegativity. δ⁺A—Bδ⁻

Polarisability Chemical Bonding & Molecular Structure C·m²/V The ease with which the electron cloud of an atom, ion or molecule can be distorted by an external electric field. μ_induced = α × E

Polarising Power Chemical Bonding & Molecular Structure Dimensionless The ability of a cation to distort the electron cloud of a neighbouring anion. ∝ charge / radius²

Polyatomic Ion Foundations of Chemistry C (charge) A covalently bonded group of atoms that carries an overall electrical charge and behaves as a single unit in reactions.

Polydentate Ligand Inorganic & Coordination Chemistry Dimensionless A ligand that binds to a single metal centre through three or more donor atoms.

Polymer Biochemistry & Polymer Chemistry g/mol A large molecule built from many repeating structural units joined by covalent bonds. –(A)ₙ–

Polymorphism States of Matter & Gas Laws Dimensionless The ability of a single substance to exist in more than one crystalline form.

Polyprotic Acid Acids, Bases & Salts mol/L An acid capable of donating more than one proton per molecule. H₂A ⇌ H⁺ + HA⁻ ⇌ 2H⁺ + A²⁻

Polysaccharide Biochemistry & Polymer Chemistry Dimensionless A carbohydrate polymer built from many monosaccharide units linked by glycosidic bonds. (C₆H₁₀O₅)ₙ

Terms starting with P