2. standard: i & e (1n) terms: 87 article: 90 & 110 mastering concept: 112(29-33) Homework Cornell notes: 4.1 sec. assessment: 91(1-4) 1

3. Section 4-1 Section 4.1 Early Ideas About Matter Compare and contrast the atomic models of Democritus, Aristotle, and Dalton. Understand how Dalton's theory explains the conservation of mass.

4. theory: an explanation supported by many experiments; is still subject to new experimental data, can be modified, and is considered successful if it can be used to make predictions that are true

5. Section 4-1 Section 4.1 Early Ideas About Matter (cont.) Dalton's atomic theory The ancient Greeks tried to explain matter, but the scientific study of the atom began with John Dalton in the early 1800's.

6. Section 4-1 Greek Philosophers (cont.) Many ancient scholars believed matter was composed of such things as earth, water, air, and fire. Many believed matter could be endlessly divided into smaller and smaller pieces.

7. Section 4-1 Greek Philosophers (cont.) Democritus (460–370 B.C.) was the first person to propose the idea that matter was not infinitely divisible, but made up of individual particles called atomos. Aristotle (484–322 B.C.) disagreed with Democritus because he did not believe empty space could exist. Aristotle’s views went unchallenged for 2,000 years until science developed methods to test the validity of his ideas.

8. Section 4-1 Greek Philosophers (cont.)

9. Section 4-1 Greek Philosophers (cont.) John Dalton revived the idea of the atom in the early 1800s based on numerous chemical reactions. Dalton’s atomic theory easily explained conservation of mass in a reaction as the result of the combination, separation, or rearrangement of atoms.Dalton’s atomic theory

10. Section 4-1 Greek Philosophers (cont.)

11. Greek Concept of toms Created in 400 B.C.

12. Who suggested the existence of atoms? Democritus (460 B.C. – 370 B.C.) – Matter consisted of tiny, indivisible, unchangeable particles called_____________. Atom

13. John Dalton (1766-1844) Atomic Theory 1.All elements are composed of tiny _________ particles called atoms. 2.Atoms of the same element are identical. 3.Atoms of different elements can combine to form ___________ (always have the same whole number ratios). 4.Chemical reactions occur when atoms are separated, joined, or rearranged. indivisible Compound Gold Atoms Hydrogen Atoms

14. How is an atom of hydrogen different from an atom of oxygen? Elements are different because they contain different numbers of _____________. _________________: the number of protons in the nucleus of an atom of that element. Protons Atomic Number

15. Mastering Concept 112 (29-33) 29. Who originally proposed the concept that matter was composed of tiny indivisible particles? (4.1) 29. Democritus

16. Mastering Concept 112 (29-33) 30. Whose work is credited with being the beginning of modern atomic theory? (4.1) 30. John Dalton

17. Mastering Concept 112 (29-33) 31. Explain why Democritus was unable to experimentally verify his ideas. (4.1) 31. The scientific instruments necessary to research matter at the atomic level had not been invented yet.

18. Mastering Concept 112 (29-33) 32. State the main points of Dalton’s atomic theory using your own words. Which parts of Dalton’s theory were later found to be in error? Explain why. (4.1) 32. See Figure 4-4. Dalton was wrong about atoms being indivisible and all atoms of an element being identical.

19. Mastering Concept 112 (29-33) 33. Explain how Dalton’s atomic theory offered a convincing explanation of the observation that mass is con- served in chemical reactions. (4.1) 33. Mass is conserved because atoms cannot be created, divided, or destroyed. Chemical reactions involve only the separation, combination, and rearrangement of atoms.