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Chemistry Chapter 4 Name_______________________ Hour__________Date__________ Chapter 4.1 – Early Ideas About Matter 1. What did many Greek philosophers believe matter was composed of? 2. What did Democritus (460-370 B.C.) believe about matter? And about atoms? 3. What was Aristotle’s (384-322 B.C.) belief on atoms? 4. Explain Dalton’s (1766-1844) Atomic Theory. Use Table 4.2 on p. 104. 5. How does Dalton’s atomic theory explain the law of conservation of mass? Chapter 4.2 – Defining the Atom 1. Define atom. 2. What instrument is used to view individual atoms and how does this instrument work? 3. The instrument allows scientists to do what with the atoms? (Nanotechnology, p. 107) 4. What is a cathode-ray tube (Figure 4.6) and what has it allowed researchers to study? 5. The accidental discovery of the cathode ray from Sir William Crookes led to the invention of television. Explain briefly Crookes’ observations and thus his discovery of the cathode ray. 6. Define electrons. 7. How did English physicist J. J. Thomson (1856-1940) determine the charge-to-mass ratio of the charged particle/electron? 8. Dalton’s atomic theory was proven false by Thomson’s significant finding. Explain his conclusion. 9. American physicist Robert Millikan (1868-1953) developed the oil-drop apparatus to determine the charge of an electron. A single electron carries what charge? 10. How did Millikan control the rate of a droplet’s fall? 11. How did he calculate the mass of an electron ? 12. What explanation does Thomson’s plum pudding model give about the charge of the atom? 13. What was the purpose of the 1911 experiment conducted by Ernest Rutherford’s (1871-1937) and his colleagues ? 14. Reading Rutherford’s experiment, how did they determine if the atoms in the gold foil deflected the alpha particles? 15. What were the results of the experiment? 16. Rutherford concluded that the plum pudding model was incorrect. Explain his nuclear model (Figure 4.13 ). 17. What caused the deflections? 18. Rutherford’s nuclear model introduced the concept of the NUCLEUS which contained positively charged PROTONS. Rutherford’s coworker, physicist Chadwick (1891-1974) showed that the nucleus also contained neutral particles called NEUTRONS. Define the terms proton, neutron, and electron, include the symbols. (a) Proton (b) Neutron (c) Electron 19. Draw Rutherford’s model of the atom (fig. 4-14) label each part. 20. What identifies the atom of a particular element? 21. What is the atomic number? 22. Because atoms are neutral, the atomic number can also determine what two things about the atom? 23. Define the term ISOTOPE. 24. How do the mass of Isotopes vary as the neutron number changes? 25. How are isotopes of each element identified? 26. How do you determine mass number? Write an equation that illustrates this 27. Define one atomic mass unit (amu). 28. Define ATOMIC MASS 29. How does atomic mass differ from mass number? (We will not be covering Sect. 4.4, p. 122-124 in this unit.)