Chp. 4 Biology Study Guide
BIOLOGY STUDY GUIDE CHAPTER 4– THE CHEMICAL BASIS OF LIFE Matter = anything that takes up space and has mass (major types of matter = solid, liquid, and gas) Any type of matter is made of one or more elements. o Element = a substance that cannot be broken down into other substances by regular chemical processes. (examples: gold, silver, mercury, etc.) There are approximately 25 elements necessary for life. • Examples: oxygen, carbon, hydrogen, nitrogen, calcium, phosphorous, etc. • Trace elements = those elements that make up less than 0.01 percent of your body mass (examples: iodine, iron, copper, etc.) Compounds = a substance containing two or more elements; these elements are always present in this compound in the same ratio o For instance, water is a compound where hydrogen and oxygen are combined. The ratio of hydrogen to oxygen in water is always 2:1. (Remember that the chemical formula of water is H2O.) o Compounds have different characteristics than the elements that make them up. (Water is liquid at room temperature, but when hydrogen and oxygen are by themselves, they are gases at room temperature.) Atoms = smallest possible piece of an element o A better definition of an atom may be: the most basic unit of matter that cannot be broken down into smaller pieces by ordinary chemical methods. o This can be confusing, because when you read the above definition or when you start looking at the periodic table in class, is oxygen an atom or an element? o An element is essentially the same as an atom. Why do we bother with two different words? • An element is the most common version of an atom. The element you see on the periodic table for oxygen is the most common version of the oxygen atom that exists in nature. There are several different kinds of oxygen atoms (with different numbers of neutrons than the one found on the table), but they are not as commonly found in nature. All atoms are made of even...
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