Alan wrote the following examples of changes in substance. example a: a camp fire is lighted. example b: plants convert carbon dioxide and water into qlucose and oxygen. which statement is correct? a. both are examples of physical change. b. both are examples of chemical change. c. example a describes physical change and example b describes chemical change. d. example a. describes a chemical change and example b describes a physical change.

Hydroelectricity provides about 7 percent of the electricity generated in the united states. (a) explain how a hydroelectric power plant converts energy stored in water into electricity. (b) identify two factors that determine the amount of electricity that can be generated by an individual hydroelectricity power plant. (c) describe the two main types of land-based hydroelectric power plants. (d) describe two economic advantages and two environmental disadvantages of hydroelectricity.