Students make sense of the phenomenon of electricity as they gain an understanding of the difference between electrical conductors and insulators. Using the science and engineering practices of generating and comparing solutions and making observations, students gain experience recognizing a conductor by its material properties. Students explore the disciplinary core ideas of energy and material properties and the crosscutting concepts of energy transfer and standard units in preparation for the associated hands-on activities. In one activity, students build a conductivity tester to determine whether different objects are conductors or insulators. In another activity, students use their understanding of electrical properties to choose appropriate materials to design and build their own basic circuit switch.