2 Safety Students must wear: Closed shoes Slacks or skirts that come to the anklesSleeved shirtsLab coat or lab apronIndirect vent or unvented chemical splash proof goggles. No impact glasses or visorgogs are permitted
3 What Students Can Bring pHydrion paperhand lens9 volt conductivity tester (no testers will be allowed that run on 120 volts.)Beral pipettes or eye droppersContainers appropriate for testing conductivity and solubility (spot plates, beakers, etc. are fine)Test tube holder and test tube rack if using test tubesSpatulaStirring rod
4 What Students Can’t Bring Reference MaterialsCalculatorsWriting instruments of any kindANY materials other than on previous slideRanking below those who have followed the rulesThe Penalty?
5 What Supervisors Will Provide 1.0 M NaOH1.0 M HClDistilled (deionized) waterTwo different colored writing implementsPaper TowelingThe observation sheetThe questions/scoring sheet
6 What Supervisors MAY Provide ThermometerBalanceHot plateAnything else the supervisor decides to distribute. If the supervisor feels instructions are needed in order to use something provided, the instructions will be available
7 Main Focus Observations The distinction between an observation and an inferenceHow to prepare studentsScoring the ExamResources
8 ObservationsEmphasize to students that the purpose of this lab is NOT to identify the powder. (That is the Science Crime Buster event-not this one)The purpose is to characterize the powder!This event hits all of the Middle School National Physical Science Standards.Therefore it is an excellent event to actually use in the classroom to teach observation and the difference between observation and inference
9 ObservationsStudents need to learn to write down observations, not inferences.Students need to be as specific as possible.While both flour & cornstarch might at first glance be described as “white powders”, flour is generally more of an ivory white or creamy white, whereas cornstarch is more bright whiteStudents should be as quantitative as possibleStudents should state how many grams of the substance were attempted to dissolve in how many ml of water and from what temperature to what temperature the water changed during how long a time
10 ObservationsStudents should do tests on the reagents they are given as well as the powder.If you do not know for sure if the liquid you are attempting to dissolved the solid in does or does not conduct electricity, you can not say for sure what the solid didIf you do not know what the temperature of the liquid was before you start dissolving, you can not know by how much the temperature changed.
11 Observation & Inference If the student attempts to dissolve the .1g of the powder in 1 ml of water and the temperature goes down from 22.1C to 20.9C, that is an observationIf instead the student writes down that dissolving the powder is an endothermic process, that is an inference.You would use the first observation to answer the question of whether or not the dissolving is exothermic or endothermic.But you would get less points for answer 2
12 ObservationsThe questions the event supervisor is likely to ask can be divided into two main categories:“Standard Questions”What color is the powder?Is it a powder or a crystal or a granuleEtc“Powder specific questions”You can not ask if dissolving the powder in water is exothermic if the powder is insoluble in water.Etc.
13 How to Prepare Students You will want to create a number of tests for various powders where the team members preparing for the event practice making observations and then get the questions and have to use their observations to answer the questions.The tougher you can make your questions, the better the students will get.It is not easy to think of observations to make on a single powder with only a few reagents for 20 minutes.
14 Scoring the Exam This is best done as a group activity if possible If there are few enough exams (<~12) two people can divide the exams between them.Then the observations that support each question are looked at and ranked.The best observations are awarded 5 points, the next best 4“Observations” that are really inferences can get a maximum of only 3.Incomplete observations receive less points