Acids, Bases, and the pH Scale

This final page introduces the concepts of acids and bases in the context of water, an important topic in Structure of water and hydrogen bonding AP Biology.

Definition: The pH scale is a measure of the acidity or basicity of a solution, ranging from 0 (most acidic) to 14 (most basic).

The page explains that water can act as both an acid and a base, making it amphoteric. This property is crucial for many biological processes.

Vocabulary: Amphoteric substances can act as both acids and bases.

The concept of neutrality on the pH scale is introduced, explaining that a neutral solution has a pH of 7, where the rates of proton gain and loss are equal.

Highlight: Understanding acids, bases, and the pH scale is crucial for many biological processes, including enzyme function and cellular homeostasis.

The page concludes by noting that solutions with a pH lower than 7 are acidic, while those with a pH higher than 7 are basic, providing a foundation for further study of acid-base chemistry in biological systems.

Water's Properties and Biological Significance

This page delves deeper into water's properties and their biological importance in AP Biology Unit 1.

Water's role as a solvent is explained through the concepts of solutions, solvents, and solutes. The page emphasizes how water's solvent properties are crucial for cellular processes.

Definition: A solution consists of a solvent (the dissolving medium, usually water in biological systems) and a solute (the substance being dissolved).

The concept of cohesion is introduced, explaining how hydrogen bonds between water molecules create strong attractions, leading to high surface tension.

Example: Water striders can walk on water due to the high surface tension created by water's cohesive properties.

The page also covers water's high specific heat and its importance in temperature regulation. This property is linked to the energy required to break and form hydrogen bonds.

Highlight: Water's high specific heat helps regulate temperature in living organisms and ecosystems, making it cooler near large bodies of water and enabling sweating as a cooling mechanism.

Adhesion and capillary action are explained, demonstrating how water interacts with other substances and moves through narrow spaces.

Vocabulary: Capillary action is the ability of a liquid to flow against gravity in narrow spaces due to adhesive and cohesive forces.