Beginner Topic 619 of 1102 Inorganic Chemistry
Water Chemistry
Water is a polar amphoteric solvent with hydrogen bonding and high heat capacity.
In-depth explanation of Water Chemistry
Water is a small polar molecule with an H-O-H angle of about 104.5 degrees, so each molecule can form up to four hydrogen bonds. This network explains its high boiling point of 100 degrees C at 1 atm, its high specific heat capacity of about 4.18 J per gram per kelvin, and its high surface tension. Water dissolves ionic compounds well because its dipoles stabilize the separated ions. It is amphoteric, and its autoionization constant Kw is 1.0 x 10^-14 at 25 degrees C. Its density is greatest at 4 degrees C, which is why ice floats and lakes freeze from the top down.
Going deeper: Water Chemistry
Key ideas: Water is amphoteric with Kw = 1.0e-14 at 25 C, so pH + pOH = 14. Its high boiling point comes from about four hydrogen bonds per molecule, and density maximum is at 4 C. Hard water has Ca2+ and Mg2+; temporary hardness (bicarbonates) is removed by boiling, permanent hardness (sulfates, chlorides) by washing soda or ion exchange.
Common mistakes and connections: Students think boiling removes all hardness, but it only precipitates carbonates from bicarbonate. Another error is saying ice is denser than water; the open hexagonal lattice makes it less dense, so it floats. Pure water pH 7 only at 25 C, because Kw changes with temperature. Links to water treatment and solvation.
Visualization of Water Chemistry
Bent water molecule with an H-O-H angle near 104.5 degrees; its polarity allows up to four hydrogen bonds per molecule and explains its unusual properties. The interactive lesson shows this as a live animation or chart.
Worked example and use case
At 25 degrees C pure water has [H3O+] = [OH-] = 1.0 x 10^-7 mol/L, so its pH is 7.00.
Frequently asked questions about Water Chemistry
What is Water Chemistry?
Water is a polar amphoteric solvent with hydrogen bonding and high heat capacity.
Is Water Chemistry a beginner, intermediate or advanced topic?
Water Chemistry is a beginner topic in Inorganic Chemistry. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Water Chemistry?
Study these earlier topics in Inorganic Chemistry first: Hydrogen, Isotopes of Hydrogen, Hydrides.
What comes after Water Chemistry?
The next topics in Inorganic Chemistry are Heavy Water and Hydrogen Peroxide.
Can I practise Water Chemistry with quizzes?
Yes. The interactive lesson includes a self-check question on Water Chemistry, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Water Chemistry fits in Inorganic Chemistry
Water Chemistry is topic 4 of 113 in Inorganic Chemistry.