BiochemistryLesson 1 of 2 in the course Chemistry of Life

Water's Molecular Properties, Solvent Behavior, and pH Regulation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

A water molecule contains two hydrogen atoms bonded to one oxygen atom. The electrons in each polar covalent bond are shared unequally: they spend more time near oxygen than hydrogen. As a result, oxygen has a slight negative charge, while each hydrogen has a slight positive charge. The molecule as a whole has no overall charge, but its charges are distributed unevenly, making it polar.

All flashcards

What makes water a polar molecule?
Electrons in water's covalent bonds are shared unequally, giving oxygen a slight negative charge and the hydrogens slight positive charges.
What is a hydration shell?
A layer of water molecules arranged around dissolved ions, helping keep them dispersed in solution.
How do cohesion and adhesion differ?
Cohesion is attraction among water molecules; adhesion is attraction between water and other substances.
How does evaporation cool the surroundings?
Escaping water molecules require energy to overcome attractions, drawing heat from the liquid and its surroundings.
What does a buffer do?
A buffer absorbs excess H⁺ or OH⁻ and resists changes in pH.

Quiz questions

  1. When sodium chloride dissolves in water, which part of a water molecule orients toward a sodium ion?Answer: The slightly negative oxygen end.
  2. What property of water's surface can support a gently placed needle?Answer: Surface tension, produced by cohesion among water molecules.
  3. How do cohesion and adhesion help move water through plants?Answer: Adhesion helps water interact with passageway walls, while cohesion keeps water molecules connected.
  4. What happens to pH when hydrogen-ion concentration increases?Answer: The pH decreases.
  5. How can bicarbonate help limit a fall in body pH when excess H⁺ is present?Answer: It combines with H⁺ to form carbonic acid.

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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