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 erroris a method of analyzing data that tells how accurate our results are • Actual means what YOU got in the lab. • Make sure you subtract before you divide!
Percent Error • 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