The following paragraphs are meant to summarize the activity you did in class. Compare this summary to the one your teacher asked you to write. For homework use your comparison to write down all changes you would need to make to your summary to make it accurate and complete. If you notice something that this summary leaves out then please bring it to the attention of your teacher. Your changes list should be typed and handed in to earn credit for this assignment.
In this activity we learned how to identify types of chemical reactions by looking at written-out chemical equations. Just as living things can be classified into groups such as mammals, plants, and fish chemical reactions can be classified as well. In this activity there were four types of reactions. A fifth type, combustion, is also of some interest. One type of reaction is called a synthesis reaction. In a synthesis reaction two substances combine to make a single new substance. The reactants may be either elements or compounds or one of each. The product is always a compound.
Another type of reaction, which is more or less the reverse of a synthesis reaction, is a decomposition reaction. In a decomposition reaction a compound breaks down into other compounds or elements. The products of a decomposition may be compounds, elements, or both.
The third type of chemical reaction is called a single replacement reaction. In this type of reaction part of an ionic compound is removed and replaced with a new element. In the process the element removed from the compound becomes a pure element instead. One way to recognize this type of reaction is to recognize that an ion loses its charge to become neutral and a neutral element gains a charge to become an ion.
The fourth type of reaction is called a double replacement reaction. This reaction type involves a pair of ionic compounds which exchange ions to form a different pair of compounds. The cation from each compound joins up with the anion from another. In this type of reaction no elements or ions change their charges. There are three basic categories of double replacement reactions. The first is called a precipitation reaction. In this type of reaction one of the two product compounds is insoluble in water. The insoluble compound precipitates by forming a solid that collects the bottom of a reaction vessel like snow on the ground. The second type of double replacement reaction is an acid-base reaction. This type of reaction involves reacting a compound containing the H+ (hydrogen) ion with one containing the OH– (hydroxide) ion. The products always include liquid water and a salt. The word salt here has a broader meaning than usual: it means any combination of a anion from an acid with a cation from a base. The third type involves the formation of a gas.
Finally, there is another type of reaction not covered in this activity that is worth knowing about. When a hydrocarbon burns in the presence of oxygen it produces carbon dioxide and water. This true no matter what the formula of the hydrocarbon. This type of reaction is called a combustion reaction.