In the following video Paul Andersen explains how light can be treated as both a particle and a wave. Physicists use scale to determine which model to use when studying light. When the wavelength of light is equivalent to the size of the object a wave model is used. [3:34]

In this video, Paul Andersen describes both weather and climate. Weather refers to the day-to-day conditions on the Earth's surface, including temperature, wind, humidity, air pressure, and precipitation. Climate means the long-term conditions on the Earth's surface. Both climate and weather are determined by sunlight, water, landforms, and life forms. [7:47]

In the following video Paul Andersen explains how the kinetic energy gained by an object is equivalent to the work done on the object. The force on the object must act parallel or antiparallel to the motion of the object to do work. [8:12]

In the following video Paul Andersen explains how the mechanical energy added or removed from a system results from work. For work to occur a force must act parallel to the displacement of the system. Since work and energy are equivalent the work-energy theorem allows of for calculating the work as the change in kinetic energy. [7:01]

In the following video Paul Andersen explains how buffer solutions maintain pH in a solution. A buffer solution is made up of a weak acid and its conjugate base. As strong acids or bases are added the pH remains stable. A good buffer solution has a pKa value equivalent to the pH and equal amounts of the weak acid and the conjugate base. [5:57]