What is Chemistry?

1. What is Chemistry?

2. The study of the properties of matter and the changes that matter undergoes.

3. What is the modern definition of the atom?

4. What is the modern definition of the atom? • The smallest representative particle of an element that has all of the properties of that element.

5. What is an element?

6. What is an element? • A substance that cannot be separated into simpler substances by chemical means. All atoms of an element are alike in properties and reactivities.

7. What is a molecule?

8. What is a molecule? • A molecule is formed when two or more atoms bond covalently.

9. What are the four states of matter in order of increasing energy?

10. What are the four states of matter in order of increasing energy? solid→ liquid→gas→plasma

11. What is the Law of Constant Composition?

12. What is the Law of Constant Composition? • The elemental composition of a pure compound is always the same.

13. What is the difference between a chemical and physical change?

14. In a physical change the substance alters its appearance, but not its chemical composition. • Water becomes ice, but is still H2O

15. In a chemical change, the substance is transformed into a different substance.

16. All changes of state are what type of changes?

17. All changes of state are what type of changes? • Physical

18. All combustion reactions are what type of reaction? • Chemical • Combustion reactions always have O2 as a reactant.

19. What are the three subatomic particles that chemists are concerned with?

20. Protons, neutrons and electrons

21. What is the electrical charge of a proton or electron?

22. 1.602 x 10-19C is the amount of charge per electron or proton. • Protons positive • Electrons are negative

23. For simplicity, what do we consider to be the charge on an electron or proton?

24. -1 electron • +1 proton

25. How do the number of protons and electrons compare in an atom of an element?

26. They are equal.

27. Which subatomic particles are found in the nucleus of an atom?

28. Protons and neutrons

29. What makes up most of the volume of an atom?

30. The electron cloud

31. Atoms have extremely small masses (the heaviest atom is on the order of 4 x 10-22 g) We use the amu to describe the mass of atoms and molecules. What is the amu?

32. The atomic mass unit. The mass of a proton and neutron are both considered to be 1 amu. An electron is about 2000 times smaller than a proton and is considered to be 0 amu.

33. On what element was the amu based?

34. On what element was the amu based? • Carbon -12

35. Atoms are extremely small. Most have diameters on the order of 10-10 m. What unit is commonly used to express the diameter of atoms?

36. Picometers and the Angstrom (Å) • 1 Å = 10-10 m • 1pm = 10-12 m

37. The diameter of a carbon atom is 1.54 Å, express this diameter in picometers.

38. 1.54Å x (10-10m) x (1012pm) 1Å 1m =154 pm

39. What are the four basic forces?

40. What are the four basic forces? • Gravitational • Electromagnetic • Strong nuclear force • Weak nuclear force

41. Which subatomic particle determines the identity of the element?

42. Which subatomic particle determines the identity of the element? • The number of protons determines the element • Each atom of an element has the same number of protons.

43. What are isotopes?

44. What are isotopes? • Atoms of a given element that have different numbers of neutrons.

45. What is the atomic number? • The number of protons

46. What is the mass number?

47. What is the mass number? • The total number of protons and neutrons in the atom

48. How do we identify isotopes Mass number Symbol Atomic number For example 12C 6

49. What is a nuclide

50. What is a nuclide • An atom of a specific isotope