Josiah Willard Gibbs, an American scientist discovered physical and chemical changes. He also made many important theoretical contributions to physics, chemistry and mathematics. Physical and chemical change was discovered during the year from 1876 to 1878.

The correct answer to this question is Josiah Willard Gibbs. He was born in Connecticut in 1839. Most know him for his work in discovering chemical and physical changes. However, he worked in many other fields including mathematics, chemistry, and physics.

Physical and chemical change has been discovered by Josiah Willard Gibbs. His work used to be in statistical mechanics. The things that he did every day has allowed him to discover different changes that may occur. He also realized that there are instances when the change does not make a difference with the overall composition of the item.