Regents Chemistry Midterm Review

1. Regents Chemistry Midterm Review • Unit 1 – Matter and Measure • Unit 2 – Atomic Theory and Structure • Unit 3 – Nuclear Chemistry • Unit 4 – Periodic Table • Unit 5 - Bonding • Unit 6 – Naming and Moles

2. Matter and Measure Chapters 1-3

3. Chemistry • What is Chemistry? • Study of matter and the changes it undergoes • Branches • Organic • Physical • Analytical • Biochemical • Inorganic

4. Matter • Anything that has mass and takes up space, volume • Classified into two categories • Substances (Pure) • Mixtures

5. Matter

6. Pure Substances • Element • simplest form of matter that has a unique set of properties. • Can’t be broken down by chemical means • Compounds • substance of two or more elements chemically combined in a fixed proportion • Can be broken down by chemical means

7. Mixtures • Physical blend of two or more substances • Two Types: • Homogeneous • Composition is uniform throughout • Heterogeneous • Composition is not uniform throughout

8. Separating Mixtures • Differences in physical properties can be used to separate mixtures • Filtration – Separates solids from liquids in heterogeneous mixtures • Distillation – Separates homogeneous liquid mixtures based on different boiling points • Evaporation – evaporate away liquid to leave solid • Chromatography – separation of substances based on polarity

9. Phases(States) of Matter • Solid (s) • Definite shape and volume • Particles are packed tightly together in a regular geometric pattern • Liquid (l) • Definite volume, takes shape of container • Particles can slide past each other • Gas (g) • Takes shape and volume of container • Particles are spread very far apart

10. Phase Changes • Solid  Liquid Melting • Liquid  Solid Freezing • Liquid  Gas Vaporization • Gas  Liquid Condensation • Solid  Gas Sublimation • Gas  Solid Deposition • Temperature does NOT change during a phase change

11. Identifying Substances • Physical Property • quality or condition of a substance that can be observed or measured without changing the substance’s composition • Ex: Color, shape, size, mass • Physical Change • some properties change, but the composition remains the same • Can be reversible or irreversible • Ex: melting, freezing, tearing

12. Identifying Substances (cont) • Chemical Change • change that produces matter with a different composition than the original matter • Ex. burning, rusting, decomposing, exploding, corroding • Chemical property • property that can only be observed by changing the composition of the substance. • Ex: Reactivity with acids, reactivity with oxygen

13. Energy Exchanges • Exothermic • Process when energy is released or given off • Ex: Burning, freezing • Endothermic • Process when energy is absorbed or taken in • Ex: Melting

14. Scientific Method • Observation • using five senses to make observations. • Hypothesis • proposed explanation for an observation. • Experiment • procedure used to test a hypothesis. • Analyze Data • check to see if results support hypothesis. • Theory • well tested explanation for a broad set of observations. • Law • concise statement that summarizes the results of many observations and experiments.

15. Significant Figures • Shorthand • If the decimal point is present, start counting digits from the LEFT side, starting with the first non-zero digit. 1 2 3 0.00310 (3 sig. figs.)

16. Significant Figures (cont) • Shorthand • If the decimal point is absent, start counting digits from the RIGHT side, starting with the first non-zero digit. 3 2 1 31,400 (3 sig. figs.)

17. SigFigs for Math • Addition and Subtraction • Answer has to have the same number of decimal places as least decimal places in what you are adding or subtracting • Multiplication and Division • Answer has to have same number of Sigfigs as least number of Sigfigs in what you are multiplying or dividing

18. Percent Error

19. Temperature • Measure related to the heat of an object • Measured in °Celsius or Kelvin(no degrees) • Conversion

20. Density • Amount of matter in a given amount of space • Amount of mass in a given volume

21. Back

22. Atomic Theory and Structure Chapters 4-5

23. Atom • Atoms are made of subatomic particles • Protons • Neutrons • Electrons

24. Electron • Discovered first • Negative charge (-1) • Approx mass ~ 0u • Found outside of nucleus • Valence Electron • Electrons in the outermost energy level

25. Proton • Discovered second • Positive charge (+1) • Approx mass ~ 1u • Found inside nucleus

26. Neutron • Discovered last • No charge (0) • Approx mass ~ 1 atomic mass unit (u) • Just slightly larger than a proton • Found inside nucleus

27. Atomic Structure • Atoms have no net charge • # of electrons = # of protons • Nucleus • Center of atom, contains protons and neutrons • Positive charge

28. Atomic Structure • Atomic Number • Number of protons • All atoms of the same element have the same number of protons • Mass Number • Number of protons and neutrons in an atom • # of Neutrons = Mass Number – Atomic Number

29. Chemical Symbols Mass Number • Cl-35 • Chlorine-35 Atomic Number

30. Atomic Structure • Isotope • atoms of the same element with different number of neutrons • Ion • Atom or group of atoms that have gained or lost one or more electrons • Have a charge

31. Average Atomic Mass • Atomic Mass • Weighted average based on the relative abundance and mass number for all naturally occurring isotopes • Relative Abundance • Percent of each naturally occurring isotope found in nature

32. Atomic Mass • C-12 98.9% • C-13 1.1% • Carbon = 0.989*12 + 0.011*13 = 12.011u

33. Atomic Theories • Dalton’s Atomic Model • Also called Hard Sphere Model • First model • Plum Pudding Model • Uniform positive sphere with negatively charged electrons embedded within. • Came as a result of discovery of electron

34. Rutherford Gold Foil Experiment • Shot alpha particles at gold foil • Most went through, some were deflected back • Conclusions • Atom is Mostly Empty Space • Dense positive core (nucleus)

35. Atomic Theories • Rutherford Model • Dense positive core (nucleus) • Electrons moving randomly around nucleus • Bohr Model • Dense positive core (nucleus) • Electrons in specified circular paths, called energy levels

36. Atomic Theories • Wave Mechanical Model • Dense positive core (nucleus) • Electrons in orbitals • Regions of space where there is a high probability of finding an electron • Modern (current) Model • AKA Quantum Mechanical Model, Electron Cloud Model

37. Electron Configuration • The way in which electrons are arranged in the atom • Ground State • When the electrons are in the lowest available energy level (shown on reference tables) • Excited State • When one or more electrons are not in the lowest available energy level

38. Bohr Model • Each energy level can only hold up to a certain number of electrons • Level 1  2 electrons • Level 2  8 electrons • Level 3  18 electrons • Level 4  32 electrons

39. Valence Electrons • Electrons in the outermost energy level

40. Energy Level Transitions • Electrons can move between energy levels • Gaining energy will move an electron outward to a higher energy level • When an electron falls inward to a lower energy level, it releases a certain amount of energy as light

41. Back

42. Nuclear Chemistry Chapter 25

43. Radioisotopes • Nuclei of unstable isotopes are called radioisotopes. • An unstable nucleus releases energy by emitting radiation during the process of radioactive decay • Mass and/or energy

44. Radiation • Late 1800’s – discovery of radiation • Three Types • Alpha • Beta • Gamma

45. Symbols Alpha Beta Gamma

46. Radiation

47. Radiation

48. Radiation • Three Types

49. Nuclear Stability • For smaller atoms a ratio of 1:1 neutrons to protons helps to maintain stability • C-12, N-14, O-16 • For larger atoms, more neutrons than protons are required to maintain stability • Pb-207, Au-198, Ta-181

50. Transmutations • Any reaction where one element is transformed into a different element • Nuclear Reactions • Natural • Has one reactant • Alpha and Beta Decay • Artificial • Has more than one reactant • Particle Accelerators