Chapter 21

Chapter 21 In an addition reaction, two or more substances combine to form a new compound. Polymerization, or the formation of polymers, is a series of addition reactions taking place to produce a very large molecule. A chemical reaction in which a single compound is broken down to produce two or more smaller compounds is called a decomposition reaction. In single-displacement reactions, one element replaces a similar element in a compound. AX+B-> BX+A In double-displacement reactions, ions from two compounds in solution exchange places to produce two new compounds. The formation of a precipitate occurs when one of the compounds formed in a doubledisplacement reaction is insoluble, or does not dissolve in water. It’s hard to imagine where our society would be without combustion reactions. In many reactions, less energy is required to break the bonds in the reactants than is released when bonds are formed to make new products. In these types of reactions, called exothermic reactions, some type of energy is released. Sometimes more energy is required to break the bonds in the reactants than is released from the formation of new bonds in the products. In these reactions, called endothermic reactions, more energy must be provided for the reaction to take place when released. Dissolution reactions occur when an ionic compound dissolves in water to make an ionic solutions.

Chapter 22 The process of combining the nuclei of atoms to make different atoms is called fusion. Breaking up the nucleus of an atom is called fission. The Protons and Neutrons in the nucleus are called Nucleons Fission and fusion are nuclear reactions that are reactions with the Nucleons. Atoms of the same element that differ in their number of neutrons are called isotopes. Radioactivity is how we describe any process where the nucleus emits particles or energy is known as radioactivity. In alpha decay, a particle that has two protons and two neutrons is released from an unstable nucleus. Beta Decay occurs when a neutron in the nucleus of a radioactive isotope splits into a proton and an electron. Gama Decay involves the release of high-energy, electromagnetic radiation from the nucleus of an atom. Unstable isotopes emit three kinds of radioactive decay. These include alpha particles, beta particles, and gamma rays. Half-life means that there is a certain length of time after which half of the radioactive element has decayed. Radioactive Isotopes are commonly used as tracers in medicine and science. It is possible to figure out the age of objects made from plants or animals that are between 50,000 and a few thousand years old using carbon dating. Plants, using the process of photosynthesis, can convert this abundant energy source into things we like to eat, wear, and use.