A principle, known as the equation of conservation, describes how the speed of a fluid changes as it flows through a pipe . Essentially, it declares that for an constant density liquid, the mass flow rate remains constant along a pathway . Mathematically, this translates expressed as A₁V₁ = A₂V₂,

Before contemporary methods of organizing elements, scientists struggled to the known elements. One early attempt was made by Johann Wolfgang Döbereiner, a German chemist who noticed a striking pattern among certain groups of chemicals. He proposed that three elements with similar traits could be