Transition
Transition refers to the coordinated social, medical, and surgical interventions undertaken by individuals with gender dysphoria to align their external presentation and bodily characteristics with those typically associated with the opposite biological sex.[1] These steps commonly include social transition (adopting names, pronouns, clothing, and mannerisms aligned with the desired sex), medical interventions (such as puberty blockers, cross-sex hormones to induce secondary sex characteristics of the opposite sex), and surgical procedures (including mastectomy, phalloplasty, or vaginoplasty to modify genitalia and other features).[2] Biological sex, however, remains unchanged, as it is defined by an organism's organization for producing small (sperm) or large (ova) gametes, a dimorphic trait immutable by current medical technology.[3] The phenomenon has seen exponential growth since the mid-2010s, particularly among adolescents and young adults, with referral rates to gender clinics rising dramatically—often by factors of thousands in Western countries—and shifting toward predominantly natal females.[4] This surge coincides with expanded access to social media and peer influences, raising questions about social contagion and underlying comorbidities like autism spectrum disorders or trauma, which are overrepresented in clinic populations.[4] Empirical evidence on outcomes is limited by methodological weaknesses, including short follow-up periods, high dropout rates, and reliance on self-reported satisfaction rather than objective measures.[5] For adults, some systematic reviews report reduced dysphoria and improved quality of life post-surgery, though complication rates for procedures like phalloplasty exceed 75%, and mental health challenges such as depression and suicidality often persist at elevated levels compared to the general population.[6][5] Among youth, desistance rates are notably high—ranging from 60% to over 90% in pre-pubertal cohorts followed into adolescence or adulthood—suggesting many cases resolve without intervention.[7][8] Medical transitions in minors carry irreversible risks, including infertility, compromised bone health, and potential impacts on brain development, amid weak evidence of net benefits; independent reviews like the UK's Cass Review have highlighted this evidentiary gap, prompting restrictions on puberty blockers and hormones for those under 18 in several jurisdictions.[9][10] Controversies persist over informed consent, with detransitioner testimonies underscoring regret linked to inadequate psychological screening, though long-term regret rates vary and are understudied due to follow-up challenges.[5]Physical Sciences
Phase transitions in physics
Phase transitions in physics describe the transformation of a thermodynamic system between distinct phases of matter, such as solid, liquid, or gas, occurring at specific temperatures and pressures where macroscopic properties like density or entropy change abruptly.[11] These transitions are governed by the minimization of the Gibbs free energy, with phases coexisting at equilibrium along phase boundaries in the phase diagram.[12] Classified by the Ehrenfest scheme based on discontinuities in derivatives of the free energy, first-order phase transitions exhibit jumps in the first derivatives, such as volume or entropy, accompanied by latent heat absorption or release without temperature change during the process.[12] For water at standard atmospheric pressure, the solid-liquid transition (melting or freezing) occurs at 0°C with a latent heat of fusion of 334 kJ/kg, while the liquid-gas transition (boiling or condensation) happens at 100°C with a latent heat of vaporization of 2256 kJ/kg.[13] These transitions involve hysteresis and nucleation, reflecting metastable states separated by an energy barrier.[11] Second-order phase transitions, in contrast, show continuous first derivatives but discontinuities in second derivatives like specific heat or compressibility, with no latent heat involved as entropy remains continuous.[12] Examples include the ferromagnetic-to-paramagnetic transition in materials like iron at the Curie temperature, where magnetization (the order parameter) vanishes continuously, and the normal-to-superconducting transition in type-I superconductors below a critical temperature.[12] In the Ising model for ferromagnetism, the critical temperature T_c marks a second-order transition where correlation length diverges, leading to power-law behaviors in properties like susceptibility \chi \propto (T - T_c)^{-1} near T_c.[12] Near critical points, where first-order lines terminate, systems exhibit critical phenomena characterized by universal scaling laws and critical exponents independent of microscopic details, as described by renormalization group theory.[12] For the liquid-gas critical point in fluids, differences in density between phases scale as \rho_{\text{gas}} - \rho_{\text{liquid}} \propto (T_c - T)^{0.32}, with divergences in compressibility \kappa \propto (T - T_c)^{-1.2}.[12] These features arise from symmetry breaking and long-range correlations, unifying diverse transitions across universality classes.[12]Chemical transitions
In chemistry, phase transitions—often termed chemical transitions in the context of studying pure substances and mixtures—describe the physical processes by which a substance changes between states of matter, such as solid to liquid or liquid to gas, without altering its molecular composition. These transitions are governed by intermolecular forces specific to the chemical structure of the substance, including hydrogen bonding in water or van der Waals interactions in hydrocarbons, and occur at characteristic temperatures and pressures where the Gibbs free energy of the phases is equal.[11][14] The primary types of phase transitions include melting (solid to liquid), vaporization (liquid to gas), sublimation (solid to gas), and their reverses: freezing, condensation, and deposition. Melting requires overcoming lattice energy in the solid phase, as seen in ice transitioning to water at 0°C and 1 atm, absorbing 6.01 kJ/mol of heat (enthalpy of fusion). Vaporization, such as water boiling at 100°C and 1 atm, demands 40.7 kJ/mol (enthalpy of vaporization) to disrupt cohesive forces entirely. Sublimation, exemplified by dry ice (solid CO₂) at -78.5°C and 1 atm, combines both processes with an enthalpy of 25.2 kJ/mol. These values reflect the chemical identity's influence on transition energetics, with hydrogen-bonded networks like in H₂O yielding higher latent heats than nonpolar molecules like CH₄ (8.2 kJ/mol fusion)./Text/5:_Energy_and_Chemical_Reactions/5.3:_Energy_and_Phase_Transitions)[15][16] Phase transitions are classified as first-order, involving latent heat and discontinuous changes in properties like volume (e.g., melting), or second-order, with continuous changes and no latent heat, such as the glass transition in amorphous polymers like polystyrene at around 100°C, where rigidity shifts to rubbery behavior without crystallization. In chemical applications, polymorphic transitions between crystal forms are critical; for instance, carbon's graphite-to-diamond conversion under high pressure (above 10 GPa at 2000°C) alters density from 2.26 g/cm³ to 3.51 g/cm³ due to rearranged covalent bonds, though thermodynamically metastable. Such transitions impact pharmaceuticals, where polymorphs of aspirin exhibit different solubilities, affecting bioavailability.[11][17]| Transition Type | Example Substance | Temperature (°C at 1 atm) | ΔH (kJ/mol) |
|---|---|---|---|
| Melting | Water (ice) | 0 | 6.01 |
| Vaporization | Water | 100 | 40.7 |
| Sublimation | CO₂ (dry ice) | -78.5 | 25.2 |
| Freezing | Water | 0 | -6.01 |