Water Science Quiz

Water

• Water is a vital substance for life, making up a significant portion of most organisms.
• The human body consists of approximately 60% water predominantly found in extracellular fluids (surrounding cells) and within cells.
• Water's unique properties result from its polar nature, with the oxygen atom carrying a partial negative charge (δ-) and the hydrogen atoms bearing a partial positive charge (δ+).
• This polarity enables water molecules to form hydrogen bonds with each other and other molecules containing N-, O-, or S-containing functional groups.
• Hydrogen bonds are primarily electrostatic attractions, but also exhibit some covalent characteristics, creating a preferred orientation and directionality.
• Each water molecule can potentially participate in four hydrogen bonds, contributing to its unusual properties.

Properties of Water

• Water remains liquid at biologically relevant temperatures, allowing organisms to interact with it, live in and on it, and utilize it as a solvent.
• Water exhibits its highest density at 4°C, causing ice to float.
• Water has a high latent heat, meaning a large amount of heat energy is required to change its state from liquid to gas.
• Water serves as an excellent thermal buffer due to its high specific heat capacity, enabling it to absorb and release heat without drastic temperature changes.
• Water molecules exhibit cohesion, sticking to each other, and adhesion, adhering to other surfaces.
• This cohesion and adhesion contribute to water's high surface tension.
• Water is an excellent solvent, readily dissolving many substances, and can also act as a reactant in various chemical reactions.

Acids, Bases, and pH

• Pure water exhibits a slight tendency to ionize, resulting in small concentrations of H+ and OH- ions.
• The ionization of water is described by the dissociation constant, Kw, which indicates the relative concentrations of hydrogen and hydroxide ions.
• At neutral pH, the concentration of H+ ions equals that of OH- ions, having a value close to 10−7 mol L−1 at 25 °C.
• Acidic solutions contain a higher concentration of H+ ions (pH < 7), while basic solutions have a lower concentration of H+ ions (pH > 7).
• pH is a logarithmic scale, meaning a one-unit change in pH corresponds to a ten-fold change in H+ ion concentration.
• The physiological pH of human blood is near-neutral, ranging from 7.1 to 7.4.

Classification of Substances Based on pH

• Acids release H+ ions in solution, acting as proton donors.
  • Strong acids ionize almost entirely in water, releasing their hydrogen ions completely.
  • Weak acids ionize partially in water, not releasing all their hydrogen ions.
• Bases release OH- ions in solution or accept protons.
  • Strong bases ionize almost entirely in water, releasing their hydroxide ions completely.
  • Weak bases ionize partially in water, not releasing all their hydroxyl groups.
• Amphoteric substances can act as both acids and bases, such as water and amino acids.

Importance of pH in Body Fluids

• Blood pH: 7.1 - 7.4 (any change can be fatal).
• Urine pH: 6.8 (slightly acidic), with changes influencing the solubility of salts and potentially leading to urinary stones.
• Gastric juice pH: 1.5 - 2 (highly acidic), with increased acidity potentially causing peptic ulcers and decreased acidity resulting in hypoacidity.

Acidosis and Alkalosis

• Acidosis: Characterized by a low serum bicarbonate level (less than 22 mEq/liter).
  • Primary metabolic acidosis: Caused by diarrhea, carbonic anhydrase inhibitors, lactic acidosis, ketoacidosis in diabetes or alcoholism, and aspirin poisoning.
• Alkalosis: Characterized by an elevated serum bicarbonate level (greater than 29 mEq/liter).
  • Primary respiratory alkalosis: Occurs with hypocapnia (pCO2 < 35 mmHg) due to hyperventilation from anxiety, fever, or high altitudes.
  • Primary metabolic alkalosis: Caused by loss of gastric HCl without loss of pancreatic HCO3, such as vomiting, or administration of some diuretics.

Compensation Mechanisms for Acidosis and Alkalosis

• Respiratory acidosis or alkalosis: Compensated by the lungs, retaining or eliminating CO2.
• Metabolic acidosis or alkalosis: Compensated by the kidneys, retaining or eliminating HCO3-.

Test your knowledge on the unique properties of water with this quiz. You'll explore everything from the distribution of freshwater to the molecular interactions that give water its distinct characteristics. Perfect for students interested in environmental science and chemistry!