Every year my students come to class with the idea that it’s colder in the winter because the earth is farther away from the sun. Where did they get this idea?
—Lauren, Aurora, Illinois
Along with notebooks and pencils, students bring some common misconceptions to science class. It’s hard to tell where students learn these misconceptions: from their friends, parents, television, movies, or other media. (I wonder, could the Flintstones be the source of the misconception that humans and dinosaurs lived at the same time?) Perhaps they hear only part of an explanation and invent the rest.
Your students are not unusual — the misconception about the seasons is pervasive. Years ago, there was a study of college graduates who also could not describe the reasons for the seasons (described in the video A Private Universe).
Many textbooks show the earth’s orbit as an exaggerated ellipse, and students know that if they sit closer to a heater they feel warmer. And so, the earth must be closer in its orbit to the sun in the summer when it’s warm (or so they think). They may not realize that their ideas are incorrect, and simply telling the students that their ideas are wrong won’t help them learn the correct ones. Even if students recognize that the earth’s axis is tilted, they may not see the connection between this tilt, the seasons, and the length of daylight time we have. For some additional resources (including visuals) for teaching this concept, go to NSTA’s SciLinks and use “season” as a keyword to get a list of related websites.
If learning involves building on our current understanding, then finding out what students know, don’t know, or think they know is important at the start of a unit. A written pretest might help, but students may have just memorized some facts or definitions without really understanding a concept. I’d recommend the types of activities in Uncovering Student Ideas in Science, by Page Keeley, Francis Eberle, and Lynn Farrin (published by NSTA Press ). The book has formative assessment “probes” to use prior to and during instruction. They are designed to have students apply what they know (or think they know) to a situation. For each probe there is a summary of the topic, a detailed description of what can be learned from the students’ responses, teaching suggestions, and a list of resources on the topic. These probes are in the form of questions or activities that could also serve as engaging activities (or “hooks”) at the beginning of a unit. There are three volumes in the series, each with 25 probes covering a wide variety of topics.
Every year that I taught life science, I had to contend with three big misconceptions: insects are not really animals, the blood in our veins is blue, and plants use minerals from the soil as food. Textbooks often show diagrams of the circulatory system with the veins colored blue, and commercials on television talk about fertilizer as “plant food.” But I still haven’t figured out the source of the insect misconception.