While developing effective scientific explanations of a common classroom experiment designed to demonstrate static electricity, students learn how materials change their state of charge and how materials with similar charges repel each other.
Draw your students’ attention to the criteria on the worksheet, and invite groups to reconsider their initial decision, this time using the criteria to guide their thinking.
Assess your students’ abilities to:
Consider providing groups with a selection of materials that vary on how strongly they hold on to electrons (see Teaching Notes about the triboelectric series). Ask groups to hypothesize which materials will create the strongest charge, and then develop experiments to test their predictions. Invite groups to develop effective scientific experiments to explain their findings.
To understand what is happening when a static charge develops, it is important to think about the atoms that make up everything around us. All matter is made up of atoms, which are themselves made up of charged particles. Atoms have a nucleus consisting of neutrons and protons. They also have a surrounding "shell" that is made up of electrons. Typically, matter is neutrally charged, meaning that the number of electrons and protons are the same. If an atom has more electrons than protons, it is negatively charged. If it has more protons than electrons, it is positively charged.
Some atoms hold on to their electrons more tightly than others do. How strongly matter holds on to its electrons determines its place in the triboelectric series. If a material is more likely to give up electrons when it contacts another material, it is considered to be more positive in the triboelectric series. If a material is more likely to "capture" electrons when it contacts another material, it is considered to be more negative. The farther the separation in the table, the greater the effect. Positive items in the series are at the top, and negative items are at the bottom:
(The above list is adapted from Nature's Electricity by Charles K. Adams.)
The behaviour of matter can be explained by the kinetic molecular theory and atomic theory.