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Please take a seat, take out your lab manual, and discuss this problem with your tablemates. Your last good ping-pong ball fell down into a narrow metal pipe imbedded in concrete one foot deep. How can you get it out undamaged, if all the tools you have are your tennis paddle, your shoe-laces, and your plastic water bottle, which does not fit into the pipe? Popcorn Lab • What safety rules do we need to follow? Clean-Up • Flasks into bin of soap water • Popcorn in the trash • All other materials back where you found them • Wash your hands and come back to class Popcorn Calculations • Work with your table to calculate percent by mass of water in your popcorn. The right answer! • Most popcorn will only pop if it has a water content of about 14.5%. The right answer! • Most popcorn will only pop if it has a water content of about 14.5%. • So how close were you? Percent Error • Percent error is a method of analyzing data that tells how accurate our results are (𝐴𝑐𝑡𝑢𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 − 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒) % 𝑒𝑟𝑟𝑜𝑟 = ∗ 100 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 • Actual means what YOU got in the lab. • Make sure you subtract before you divide! Percent Error (𝐴𝑐𝑡𝑢𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 − 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒) % 𝑒𝑟𝑟𝑜𝑟 = ∗ 100 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 • What does it mean about our data if our percent error is 0? • What does it mean about our data if percent error is greater than 100%? • What does it mean about our data if percent error is less than 0? Quiz Friday! • We will take quizzes most Fridays in this class • Usually formative scores • Covers anything we’ve done since the last quiz, including labs • This week’s: – Percent composition (mass by percent) – Popcorn lab – Wednesday and Thursday’s stuff (to be announced) ChemCatalyst You want to analyze a cadmium nitrate solution. What mass of NaOH is needed to precipitate the Cd2+ ions from 35.0 mL of 0.500 M Cd(NO3)2? Murder Mystery Day 3 • • • • Go into the lab and get your final mass Dump your waste into the provided beaker Rinse your dishes and put them in the bin Wash your hands and come back to start working on your calculations Calculations • What is the molarity of the silver nitrate? Who is the murderer? Lab Report Expectations • Expectations might vary from lab to lab • For this lab you need: – Purpose (why did we do this lab? What was the goal? – Brief description of procedure (how did you answer the question?) – Data – Calculations (show all work!) – Conclusion • What does your data mean? • How do you know? • Error analysis – what could have effected your data and HOW Suspect List • • • • • Professor Plum – 0.20-0.30 M silver nitrate Mrs. White – 0.05-0.15 M potassium iodide Mr. Green – 0.05-0.15 M silver nitrate Mrs. Peacock – >0.20 M potassium iodide Colonel Mustard – >0.30 M silver nitrate Quiz Friday! • • • • • Net ionic reactions Murder mystery lab Solubility Molarity Wednesday and Thursday’s stuff