(A) Sodium is so reactive that it must be stored under oil. The compound sodium chloride is a white solid which is essential for all living things (see below). Sodium is an extremely reactive soft metal that cannot be exposed to air or water. The properties of compounds are generally very different than the properties of the elements from which the compound is formed. Instead, the passage of an electrical current through water will produce hydrogen and oxygen gases. Water is still a compound, but one which cannot be broken down into hydrogen and oxygen by heating. When sugar is heated, it decomposes into carbon and water. Many compounds can be decomposed into their elements by heating. A chemical change is a change that produces matter with a different composition. Salt and other compounds can only be decomposed into their elements by a chemical process. Salt cannot be separated into its two elements by filtering, distillation, or any other physical process. Table salt is a compound consisting of equal parts of the elements sodium and chlorine. Recall that the components of a mixture can be separated from one another by physical means. However, it is not an element because it can be broken down into simpler substances - carbon and hydrogen. Methane is a pure substance because it always has the same composition. One of the simplest is called methane, in which there are always four times as many hydrogen particles as carbon particles. The elements carbon and hydrogen combine to form many different compounds. Platinum is very valuable at about $1650 an ounce, not quite as expensive as gold.Ī compound is a substance that contains two or more elements chemically combined in a fixed proportion. Copper is worth somewhat more, selling for approximately $3.50 per pound. Aluminum, on the other hand, only sells for about 90 cents per pound, considerably lower than gold. Gold is currently worth almost $1700 per ounce. Several of the elements are very valuable while others are quite inexpensive. They are so reactive that they can be found only in combination with other materials. Most elements do not exist as such in nature. Some elements have been known for centuries (gold, silver, iron, and copper among others) while others have been created in the lab only within the last several years. (C) Gold bars are formed and used for monetary purposes. (B) A simple skillet can be made from cast iron. (A) An oxygen tank like this is used by people with a need for breathing assistance. Likewise, one element cannot be chemically converted into a different element.Ĭhemical elements are the simplest of substances. Elements cannot be broken down into a simpler substance. Examples of well-known elements include oxygen, iron, and gold (see below). \)Īn element is the simplest form of matter that has a unique set of properties.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |