This lecture covers the macroscopic effects of van der Waals interactions, focusing on the Hamaker constant and its application to various materials. It discusses the pairwise summation of vdW interactions, the concept of the Hamaker constant, and the impact of many-body interactions and retardation effects. The lecture also explores the van der Waals forces between spheres, the comparison between physisorption and chemisorption, and the Van der Waals correction to the ideal gas law.