When you have completed this section, you should be able to
• define mixture and distinguish between mixtures and compounds;
• describe the biologically important properties of water;
• show how three kinds of mixtures differ from each other;
• discuss some ways in which the concentration of a solution can be expressed, and explain why different expressions of concentration are used for different purposes; and
• define acid and base and interpret the pH scale.
Our body fluids are complex mixtures of chemicals. A mixture consists of substances that are physically blended but not chemically combined. Each substance retains its own chemical properties. To contrast a mixture with a compound, consider sodium chloride again. Sodium is a lightweight metal that bursts into flame if exposed to water, and chlorine is a yellow-green poisonous gas that was used for chemical warfare in World War I. When these elements chemically react, they form common table salt. Clearly, the compound has properties much different from the properties of its elements. But if you were to put a little salt on your watermelon, the watermelon would taste salty and sweet because the sugar of the melon and the salt you added would merely form a mixture in which each compound retained its individual properties.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.