MCAS REVIEW DAY 2

1. MCAS REVIEW DAY 2 Final skim STUFF AND SMELLS

2. FRIDAY, JUNE 1ST (NB PG 45) • Obj: Answer MCAS questions related to Smells • Lang. Obj: use correct terms for atoms and the PT • HW: make up work! • Announcements: • Make-up work deadline is Wednesday, June 13th, 2:00pm • Chemistry MCAS is June 5th and 6th • AP Chemistry forms back ASAP! • Mr. Banks is afterschool Monday (no other days next week!)

3. CHEMCATALYST (NB PG 44) • Answer day 2 MCAS questions on notebook page 44 • note that there are ‘hints’ for some problems

4. ANSWER KEY • 18. C • 19. B • 20. C • 21. D • 22. A • 26. B • 27. D • 28. A • 29. A • 30. D • 31. A • 32. C

5. WHAT CONTENT QUESTIONS DO YOU HAVE? • How do you draw lewis dot structures?

6. “…BUT I’M NOT TAKING THE CHEMISTRY MCAS, WHY DO I HAVE TO REVIEW FOR IT?” • Yes, but everyone is taking the City Test, and… • The City Test, your final exam, is based on the MCAS • Some questions on the City Test are exactly the same as MCAS • They cover the same content

7. TODAY’S AGENDA • Answer Practice Questions 1-10 (10 min) • Q& A and Answer key (5 min) • Smells Review (20 min) • Selected MCAS Q’s practice (10 min) • Answer key, Q&A (5 min)

8. REVIEW

9. What is the molecular formula for the substance shown in the ball-and-stick model below?

10. COVALENTLY BONDED MOLECULES: • Molecular formula: The chemical formula that shows the types of atoms in each molecule and the ratios of those atoms to one another. • (ex: H2O, C2H5OH) • Chemical Name: a name that uses key words to tell the reader the properties of the molecule. Chemical names may also use numbers and can be one or two words • (ex: water, ethanol)

11. The image below is the _S_____________ _F_______________ of methane.

12. KEY TERMS FOR TODAY (HANDOUT #5) • Structural formula: A drawing or diagram that a chemist uses to show how the atoms in a molecule are connected. Each line represents a covalent bond. • Isomers: Molecules with the same molecular formula but different structural formulas.

13. Explain the HONC1234 Rule?

14. NOTES (NB PG 7) • The HONC 1234 rule is a way to remember the bonding tendencies of hydrogen, oxygen, nitrogen, and carbon atoms in molecules • Hydrogen  one bond • Oxygen  two bonds • Nitrogen  three bonds • Carbon  four bonds

15. How would you draw the Lewis Dot Structure for an atom of nitrogen?

16. Covalent Bonds • Smells Unit focuses on covalent bonds • Every line in a structural formula represents a covalent bond • Covalent bond: • Two atoms SHARING two or more valence electrons between them. • Covalent bonds are formed from the non-metallic elements on the right side of the Periodic Table

17. Lewis Dot • When we draw an atom using dots to represent the valence electrons it is called a Lewis dot symbol. • When we draw a molecule using dots to represent the valence electrons it is called a Lewis dot structure. • Nitrogen, with five valence electrons, would be drawn as follows: • Notice that the Lewis dot symbol of nitrogen has three single electrons (unpaired electrons) and one set that is paired (electron pair). This means that nitrogen has three electrons that can potentially be paired up with electrons from other atoms.

18. Bonded/Lone Pairs • Shared electrons are called bonded pairs • Pairs of electrons that are not involved in bonding are called lone pairs

19. What is the ‘octet rule’?

20. After bonding, each chlorine atom has a total of eight valence electrons surrounding it. PRE-LESSON NOTES (SEE HDT 13) • Rule of Eights/Octet rule: Nonmetal atoms combine so that each atom has a total of eight valence electrons by sharing electrons. • Each atom in the molecule has an “octet” of valence electrons. • Note that the hydrogen atoms do not follow the octet rule. • They have a total of two electrons, similar to the noble gas helium, He.

21. STEPS TO WRITING COMPLEX STRUCTURAL FORMULAS AND LEWIS DOT STRUCTURES • 1.Draw the structural formula by adding elements in this order: • a) Carbon first, in a chain • b) Add nitrogen (or other atoms that make 3 bonds) • c) Add oxygen (or other atoms that make 2 bonds) • d) Add hydrogen (or other atoms that make 1 bond • 2. Add in the lone pairs on atoms other than carbon and hydrogen • 3. Check that all atoms have an octet of electrons (when adding, each bond line counts as 2 electrons) • 4. Add double and/or triple bonds to atoms that don’t have an octet until they do. • 5. Convert this to a Lewis dot structure, change each line to a bonding pair of electrons

23. Name one ‘functional group’ we studied in the Smells Unit (ex: amine)

24. Discussion Notes (cont.)

25. Discussion

26. Discussion

27. Discussion

28. Discussion There are other functional groups.

29. What do you call the starting ingredients in a chemical reaction?

30. Notes: see back of handout #21! • A chemical reaction (rxn) is defined as a chemical transformation where bonds are broken and new bonds are formed—substances interact to produce new substances with new properties.. • A chemical reaction is the same as a chemical change. • The starting ingredients in a chemical reaction are called the reactants. • The ending compounds are called the products. (cont.)

31. Name the shapes of the molecular models below:

32. NOTES (SEE HANDOUT #27) • The following shapes can be used to describe most molecules or parts of molecules! • To predict shapes: • Draw the Lewis dot symbol for each element • Put the element with the most unpaired electrons in the center and arrange the other elements around it • Count the number of bonded pairs and lone pairs and match to the right shape Try: H2Se SiH4 HBr

34. What is the name of the molecular shape below?

35. PRE-LESSON NOTES: HANDOUT PG 31 Double or triple bonding changes the number of electron domains around an atom, affecting the overall shape of a molecule. Trigonal planar shape: A flat triangular shape found in small molecules with three electron domains surrounding the central atom. Linear shape: A geometric shape found in small molecules with two electron domains surrounding the central atom. The number of electron domains is more important in determining the structure of a molecule than is the number of atoms.

36. What type of model appears below?

37. ChemCatalyst • What similarities and differences do you see between these two different types of models? Space-filling model of citronellol Ball-and-stick model of citronellol

38. How do smell receptors work?

40. NOTES (COPY TO NB PG 41)

41. What is the difference between polar and non-polar molecules?

42. Some molecules have a slight charge on opposite ends of the molecule. Molecules that have partial charges are called polar molecules. One end of the molecule has a partial negative charge and the other end of the molecule has a partial positive charge. NOTES: SEE HANDOUT (#43, BACK)

43. Notes • Hexane was not attracted to the charged wand. So it would seem reasonable to suggest that different ends of the molecule do not have opposite partial charges. Molecules such as this are called nonpolar molecules.

44. Notes • The attraction that happens between individual polar molecules is called an intermolecular interaction or an intermolecular attraction.

46. What is electronegativity?

47. NOTES (BACK OF #47) • The tendency of an atom to attract shared electrons is called electronegativity. • Electronegativity: The tendency of an atom to attract the electrons that are involved in bonding.

48. NOTES (#47) • Dipole: A polar molecule or a polar bond between atoms. A crossed arrow is used to show the direction of a dipole. The crossed end of the arrow indicates the partial positive (+) end of the polar bond, and the arrow points in the direction of the partial negative (–) end.

49. Notes (#47) • Nonpolar covalent bonds are the only bonds in which the electrons are truly shared equally. • If the electronegativities between two atoms are even slightly different, they form what is called a polar covalent bond. • When the electronegativities between two atoms are greatly different, the bond is called an ionic bond. In the case of an ionic bond the electron of one atom is completely given up to the other atom.