The Chemistry of Water

　　The Intrinsict Nature of H2O
H2O, an exceptional molecule, not only supports life but also promotes growth across a wide spectrum of organisms. Its ubiquitous nature, accounting for 80% of the Earth’s surface, is unparalleled since it is the only element that naturally exists in the three primary states of matter—solid, liquid, and gas. Its fundamental structure is deceptively uncomplicated, comprising two hydrogen atoms bonded to one oxygen atom, as indicated by the molecular formula H2O.

　　H2O’s Unique Properties
H2O stands out due to its natural occurrence in three states on Earth. It transitions to a solid state below freezing (0 degrees Celsius or 32 degrees Fahrenheit), remains a liquid within the freezing and boiling points, and becomes a gas above boiling (100 degrees Celsius or 212 degrees Fahrenheit). H2O possesses distinct characteristics; for instance, it expands during freezing, a property not shared by most liquids. Cohesion, where H2O molecules are attracted to one another, is another defining attribute.

　　Insight into H2O’s Cycle
The hydrologic cycle provides a comprehensive and illustrated explanation of H2O’s journey on Earth.

　　Structure of H2O Molecules
H2O’s structure is formed by two hydrogen atoms and one oxygen atom, linked by electrostatic forces, with hydrogen carrying a positive charge and oxygen a negative one. This difference in charge results in cohesion, causing H2O molecules to be drawn to each other and form bonds between the hydrogen of one molecule and the oxygen of another.

　　Surface Tension of H2O
An investigation and experiment into the surface tension characteristics of H2O.

　　Interactive 3D Model of H2O
An interactive exploration of the H2O molecule’s structure, offering insights into its formation.

　　Significance of H2O’s Structure
An in-depth examination and visual representation of the structure and composition of H2O molecules.

　　H2O’s Polarity
Additional information regarding the charges within H2O molecules and their attractive forces.

　　H2O’s State Transitions
An analysis of the molecular changes that occur as H2O moves between solid, liquid, and gaseous states.

　　Solubility
The solubility of a substance in a liquid refers to the amount of solid that can dissolve within it, affected by the type of liquid, temperature, and atmospheric pressure, until a saturation point is reached.

　　Insights into Solubility
A thorough examination of solubility, including principles and concepts of equilibrium.

　　Soluble vs. Insoluble Compounds
A concise chart of compounds that are soluble or insoluble in H2O.

　　Methods to Determine Solubility
A chemistry lab guide outlining the steps to determine a substance’s solubility in H2O.

　　H2O in its Liquid State
Liquid H2O, the most visible form, covers the majority of Earth’s surface. Specific conditions dictate the transitions between H2O’s states, which must be maintained for it to remain in a particular state. Liquid H2O primarily returns to the surface through precipitation, driven by condensation that results in cloud formation and subsequent rainfall.

　　H2O on Mars
An informative discussion on why H2O cannot exist on Mars, highlighting the properties that allow its presence in certain states.

　　Sub-zero Liquid H2O
An exploration of how scientists can keep H2O in a liquid state below its freezing point.

　　Ice
Ice is the solid phase of H2O, which expands upon freezing and captures air molecules. Its buoyancy in water is due to this expansion, a rare quality among non-metallic substances. Ice can form directly from H2O vapor, as seen with frost, and is found in diverse environmental forms, including snow, hail, icebergs, and icicles.

　　Physical Properties of Ice
A detailed explanation, complete with diagrams, of the structure of frozen H2O.

　　Freezing and Expansion
An examination of the reasons and mechanisms behind H2O’s expansion during freezing.

　　Density of Ice
Molecular explanations and diagrams illustrating the density differences between H2O and ice.

　　Salt and Ice
An investigation into the interaction between salt and H2O and its effect on the freezing process.

　　Dry Ice
A study of the differences between conventional ice and dry ice.

　　H2O Vapor
H2O in its gaseous state exists as vapor, achievable above 100 degrees Celsius (212 degrees Fahrenheit) through boiling, which produces steam. H2O can also transition to vapor at lower temperatures, as evident when breath is visible on a cold day. Evaporation, the conversion of liquid H2O into the atmosphere, is another way vapor is formed.

　　Myths About H2O Vapor
A guide debunking common misconceptions about H2O vapor.

　　H2O Vapor in Space
The importance of H2O in all its states for human survival, and its presence in space.

　　The Role of H2O Vapor in Climate
An investigation into how H2O vapor contributes to regulating Earth’s climate.

　　Cloud Formation
A brief overview of how clouds are formed from H2O vapor.