Chemistry!! March 7 & 8, 2013 Ms. Boon

Catalyst  List all the things you think of when you hear the word “radioactive.”  Take out your HW!  Objective: I can define radioactivity and identify the parts of an atom involved.  Agenda:  Catalyst  Exit slip review  Investigation: Radioactive Decay  Article Review: Nuclear power plants

Unit 9 Exam and Worksheets  Exam: You may do test corrections for sections that you scored a 1 or 2. The test corrections must explain why the correct answer is correct. This will increase your grade by 1.  Short Answer: Only the top half was graded (standard 9a).  Worksheets: A check means you got a 4 and “incomplete” means you can complete the worksheets and turn them in again.

+ Exit Slip Review (1) The variety of organic molecules is possible because of carbon’s ability to form a) hydrogen bonds b) ionic bonds c) covalent bonds d) metallic bonds Why? The octet rule. Carbon wants a full outer shell with 8 electrons. It already has four, to get four more it shares.

+ Exit Slip Review (2) Carbon atoms can bond to one another forming chains and rings. They can also form multiple bonds with one another. These differences exist because when carbon atoms bond, they a) have six valence electrons to share. b) require four additional valence electrons. c) require two addition valence electrons in order to achieve a full octet. d) easily lose their valence electrons. Why? The octet rule. Carbon wants a full outer shell with 8 electrons. It already has four, to get four more it shares.

+ Exit Slip Review Simple hydrocarbons, such as propane (C 3 H 8 ) and complex biomolecules, such as cholesterol (C 27 H 46 O), are similar in structure because they contain a) metal cations. b) hydrogen bonds. c) a central structure of hydrogen atoms. d) a central structure of carbon atoms. Why? Because carbon can form 4 covalent bonds, it acts as the backbone or skeleton for biological and organic molecules.

+ Exit Slip Review (4) Which statement explains why the element carbon forms so many compounds? Carbon atoms combine readily with oxygen. Carbon atoms have very high electronegativity. Carbon readily forms ionic bonds with other carbon atoms. Carbon readily forms covalent bonds with other carbon atoms. Why? This is very similar to #3, p. 704 #15 from your HW, and #2 from the carbon article. Carbon forms very stable bonds with up to four other atoms. This allows for very large molecules. Make up assignments for Organic Chemistry standards: Standard 10a: p. 716 #2, 8, 11 p. 724 # 9, 10 Standard 10b: p. 686 #2, 9, 10 p. 704 #11

Radioactivity: Expect the Unexpected Video Focus Questions: 1. What is radioactivity? 2. What are the three types of radioactive particles described in the video and how are they different? 3. What are some uses of radioactive particles described in the video? Video: AsN-iHVA

Introduction In this activity, you will work in a group to investigate the idea of radioactive decay. Nuclei with a high proportion of neutrons to protons are generally unstable and undergo radioactive decay. In other words, the unstable nuclei changes to a more stable nuclei of a different element. This decay happens at a constant rate. The time it takes for half of the particles in a sample to decay is called a half-life. Investigation: Half-Lives and Pennies

Materials  Lined paper  Graph paper  Plastic cup  80 pennies  Textbook Investigation: Half-Lives and Pennies Procedure  Pre-Lab Tasks:  Title your paper “Half-Lives and Pennies”  Part 1: Copy the definitions of radioactivity, nuclide, and half-life  Part 2: Investigation  Follow the procedure on textbook pp. 641

Investigation: Half-Lives and Pennies Procedure  Part 2: Investigation  Follow the procedure on textbook pp. 641  Part 3: Analysis  What does your graph look like?  Compare your graph to the graph on p How is it similar or different?  Look at Table 2 at the top of p List the three isotopes with the longest half-lives. Determine how many neutrons and protons these nuclei have before they decay. (Use a periodic table.) Challenge: Read p and try practice 1-3 on p. 660.

 Part 3: Analysis  What does your graph look like?  Compare your graph to the graph on p How is it similar or different?  They have the same shape because half goes away each trial.  Look at Table 2 at the top of p List the three isotopes with the longest half-lives. Determine how many neutrons and protons these nuclei have before they decay. (Use a periodic table.)  Potassium -40, uranium-235, and uranium 238

Article Review: Nuclear Energy

Think, Pair, Share: Q: Which do you think produces more energy per gram of starting materials? (a) nuclear fission (b) combustion of fossil fuels Can you defend your decision to your partner?

Notes: The nuclear strong force  The nuclear strong force holds protons and neutrons in stable nuclei together.  This force is stronger than chemical bonds.  Breaking or changing the nuclei during fission or fusion reactions releases some of the nuclear strong force energy.  Example: fission of 1 g of uranium-235 generates as much energy as the combustion of 2700 kg of coal. If you chose “a” nuclear fission – you were correct!

Notes: The nuclear strong force  Example: fission of 1 g of uranium-235 generates as much energy as the combustion of 2700 kg of coal.

How much energy?  The energy released in a nuclear reaction is calculated using E=mc 2 E is energy (J) m is mass (kg) C is the speed of light 3.00 x 10 8 m/s Using this equation, converting 1.0 g of a substance into energy produces over KJ.

Homework  Read p , practice p. 653 #1-4

Announcements  Grades:  Pinnacle grades are up to date except for the Reaction rates/Equilibrium worksheets and the short answer portion of the exam.  All make up work is graded and entered in pinnacle  Make up work:  To get your work in before the 10 week grading period, the last day to turn in make up work is Friday March 15.  Tutoring:  Tutoring is Friday at 3:45.  BM 3 study guide:  Bring a folder to our next class to collect your worksheets, old exams, and study guide.