Water

"Water" - what is it, definition of the term

The chemical compound H₂O, composed of two hydrogen atoms bonded to a single oxygen atom, forms a polar molecule that, under standard atmospheric conditions, appears in solid, liquid, and gaseous phases; in its liquid phase it possesses a high specific heat capacity, notable surface tension, and the ability to dissolve a wide range of substances, thereby providing the medium for the majority of biochemical processes.

Detailed information

H₂O consists of two hydrogen atoms covalently bonded to one oxygen atom, forming a bent molecular geometry with a bond angle of approximately 104.5°. The polarity of the molecule creates hydrogen‑bonding networks that dictate its high surface tension, elevated boiling point (100 °C at 1 atm), and anomalous expansion upon freezing (density maximum at 4 °C).

Physical constants include a specific heat capacity of 4.18 J·g⁻¹·K⁻¹, thermal conductivity of 0.6 W·m⁻¹·K⁻¹, and dielectric constant near 80 at 20 °C. These properties enable efficient temperature regulation and solvation of ionic and polar substances.

Biological relevance for rodents such as rats and mice:

  • Daily intake ranges from 5 % to 10 % of body mass, varying with ambient temperature and diet moisture.
  • Acts as a solvent for metabolic substrates, facilitating enzymatic reactions and nutrient transport.
  • Maintains plasma osmolarity; deviations trigger osmotic stress responses controlled by vasopressin release.
  • Participates in thermoregulation through evaporative cooling and heat distribution via circulation.

Environmental considerations:

  • Sources include natural reservoirs, municipal supplies, and in‑cage water bottles designed to minimize contamination.
  • Quality parameters—pH (6.5–8.0), absence of heavy metals, low bacterial count—are critical for colony health.
  • Deprivation for periods exceeding 12 hours induces dehydration, reduced renal function, and impaired cognitive performance.

In experimental settings, precise measurement of consumption is achieved with calibrated dispensers or gravimetric methods, allowing correlation of fluid intake with pharmacological or genetic manipulations.