Arin Joshi Notes (2) PDF

Section 1: Early Ideas About Matter Essential Question: How has our understanding of matter changed over time? Democritus The Greek philosopher Democritus (460-370 B.C.E.) was the first person to propose the idea that matter is not infinitely divisible. He believed matter was made up...

Section 1: Early Ideas About Matter Essential Question: How has our understanding of matter changed over time? Democritus The Greek philosopher Democritus (460-370 B.C.E.) was the first person to propose the idea that matter is not infinitely divisible. He believed matter was made up of tiny particles called atomos, from which the English word atom is derived. Democritus believed that atoms could not be created, destroyed, or further divided. Aristotle Aristotle (384-322 B.C.E.), another Greek philosopher, did not believe that empty space could exist. Because of Aristotle’s tremendous influence on later thinkers, his belief that matter is continuous instead of being made of atoms was widely accepted for centuries. John Dalton The work done in the nineteenth century by John Dalton (1766-1844), a schoolteacher in England, marked the beginning of modern atomic theory. Dalton was able to perform experiments that allowed him to identify patterns that refined prior understandings. Based on his research, he developed new explanations for observations of chemical reactions. Dalton’s postulates, which he proposed in 1803 to explain his observations, are known as Dalton’s atomic theory. Dalton’s Postulates Scientist Ideas Dalton Matter is composed of extremely (1766-1844) small particles called atoms Atoms are indivisible and indestructible Atoms of a given element are identical in size, mass, and chemical properties. Atoms of a specific element are  different from those of another element. Different atoms combine in simple whole-number ratios to form compounds. In a chemical reaction, atoms are separated, combined, or rearranged.