Though young students may have had exposure to the Web through smartphones or a shared family computer, you may want to design a lesson to explain how the Web works on a conceptual level. Bring a bound encyclopedia into the classroom. Explain that an entire printed encyclopedia is a static, unchanging source of information compiled by a single source. Have the students look up a specific subject using the encyclopedia's index, and point out how quickly a reliable index directed them to the information they wanted. Describe the Web as an ever-changing pool of information compiled from a huge number of unrelated sources, and the search engine as a dynamic index that crawls the Web to capture that pool of information. Open a Web browser and go to your search engine of choice. Have each student search for a specific term and point out that the list of results represents information from different websites. Remind the students that no single search engine represents a complete picture of the Web, and that some pages may never appear in an index.
Consider drawing parallels between computer software and hardware and the human mind and body. Open up the CPU of an older desktop computer and label its parts with flags or printed tabs, then present it to the class. Define hardware as comparable to the physical human body. Any part of the computer that you can physically touch, whether inside or outside of the case, qualifies as hardware. Make connections between specific parts of computer hardware and the human body. For example, compare the processor to the human brain and the fan to sweat glands, lymphatic system and other elements that regulate temperature. Compare the computer's motherboard to the nervous system, and software to thoughts and feelings.
Introduce operating systems with a brief history of the personal computer. Play the PBS documentary "Triumph of the Nerds: The Rise of Accidental Empires" for your students. Rather than delving into a discussion of the basic differences between each major operating system, bring in three computers and allow the students to compare Windows, Mac OS X and Linux side by side. Ask the students to perform a series of basic computing tasks, from word processing to checking email, then ask them how the operating systems compare. If you do not have access to a computer with Linux installed, use a Linux live disc, a Linux operating system that can run in RAM from a DVD-R or USB drive on most x86 systems.
Consider following up your Web-as-encyclopedia lesson with a hands-on, in-class lesson in Web research. Remind the students that many search engines are commercial ventures that compete with each other and try to filter results for the information they consider most valuable, using their own proprietary standards. Break your class into small groups and have each one research the same topic using a different search engine. Limit each group to using no more than the first 10 search results as sources for a brief outline on the topic in question. Have each group present its sources and findings, then discuss the differences between each presentation. Use the differences between search results to drive home the idea that thorough Web research involves using multiple search engines.