Sliding friction is a force that opposes the motion of two surfaces sliding past each other. It is caused by the irregularities and roughness of the surfaces in contact. When an object is in motion on a surface, the irregularities on the surfaces interlock and create resistance to the motion, resulting in sliding friction.
Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.