{"id":5,"count":4,"description":"Eugenia Etkina November 30th. \r\nHi all, I am continuing with Chapter 12, Gases (check out the OALG file posted here for all of the activities). Please do not forget to respond to the post to make it more visible.\r\nAs the first two activities that I posted two days ago showed, this chapter is ripe for opportunities to practice our unique ISLE-based reasoning - inventing multiple explanations for the observed phenomenon, and learning to systematically reject them by systematic testing. The next two activities that I am posting today  allow for similar steps but even better. They relate to the development of the concept of pressure that moving microscopic particles exert on the walls of the container. I am posting the first activity below and AFTER  I will share my experience with the students that leads to the second activity. So, here is the first one:\r\nOALG 12.2.1 Observe and explain\r\nEquipment: a balloon.\r\nBlow up a balloon and carefully observe how its shape changes during the process. Use the idea of moving particles to explain why it expands when you blow air into it. Explain why the balloon does not expand any more when you stop blowing. Describe an experiment you can perform to test your explanation(s).\r\nThe idea here is that not only the stretched rubber of the balloon stops its expansion due to the hits of the air particles inside it, but also the particles or the outside air bumping from outside. It is this exact idea that one of my students (who never had physics before) expressed in in class. Immediately after, another student (I even remember his name, although it was 20 years ago, Jabari), Jabari, says: Wait a minute. If this is true and the particles of air are preventing the balloon from further expanding, then the un-inflated sealed balloon should expand by itself if we put it in a vacuum!  But this will never happen, how can a balloon inflate by itself?\r\nLuckily, I had a vacuum jar and a balloon handy, so we did the experiment and voila! the balloon inflated! There was this audible gasp of the whole class. Jabari predicted this crazy thing! They clapped and smiled and Jabari became my best student that year. Now, Jabari's idea is implemented in our materials. See the next activity below.\r\nOALG 12.2.2 Test multiple explanations\r\nIn the experiment in the video [https:\/\/mediaplayer.pearsoncmg.com\/...\/secs-egv2e-testing...], a partially inflated (and tied) balloon will be placed in the bell-jar and the air will be removed by the vacuum pump. Use each of the ideas you came up with in Activity 12.2.1 to make predictions about what the balloon will do when the air is pumped out of the bell-jar (state one prediction for each idea being tested). Write down your predicted outcome(s). Then watch the experiment. Which of your predictions was consistent with the experimental outcome? What is your judgment on each of the ideas you were testing?\r\nIf you read to the end, please do not forget to like the post to make it more visible.\r\n \r\nEugenia Etkina, November 28\r\nHello to everyone! Three things today: first we have a few new members - WELCOME! please read the message at the top of the group page to learn how to benefit from the materials posted here.\r\nSecond - if you read the post to the end, do not forget to respond in some way.\r\nThird, we are done with waves for now and I am moving on. The next chapter in the textbook is Chapter 12 - gases. The beginning of this chapter shows the first (chronologically, in terms of when it was invented) ISLE progression for the development of a concept - with all major attributes of the ISLE process - a simple observational experiment, noticing patterns, coming up with MULTIPLE explanations and immediately testing them and finally arriving to one of the MOST IMPORTANT IDEAS OF PHYSICS  (all by the students themselves) - that matter is made of particles and move chaotically and have spaces between them. I am pasting the sequence here with all the videos for you to see, but all of them can be done in person if you are teaching in person. All crazy ideas that are tested in the activities, came from the students.\r\n12.1 Structure of matter\r\nOALG 12.1.1 Observe and explain\r\nEquipment: 90% isopropyl alcohol, strips of paper.\r\nDip a piece of paper in rubbing alcohol (or rub the paper with alcohol) and place it on a table. Observe what happens. Describe your observations in simple words.  Note that you should observe the paper with rubbing alcohol for several minutes. Alternatively, you may view the experiment by watching the following video. [https:\/\/mediaplayer.pearsoncmg.com\/...\/sci-phys-egv2e-alg...]\r\nOne of your friends described theirs in the following way: \u201cThe alcohol disappeared gradually\u201d. What do you need to assume about the internal composition of alcohol to explain that the alcohol disappeared gradually rather than all at once?\r\nOALG 12.1.2 Develop multiple explanations\r\nMindy, Marc, Alex, and Nina are working on Activity 12.1.1. They agree that alcohol must be made of small parts to enable the paper to gradually dry. However, they disagree on the mechanism that allows these small parts to disappear. Brainstorm possible reasons for how and why the small parts of alcohol disappeared from the paper. Come up with at least four different mechanisms.\r\nOALG 12.1.3 Test multiple explanations\r\nBelow are four testing experiments that Mindy, Marc, Alex, and Nina decided to perform. Predict the outcome of each experiment described below based on each of the four mechanisms you came up with in Activity 12.1.2. (For example, if the small parts soaked into the table through the paper and we hold the paper between our fingers when drying, then the paper should not dry\u2014the table is not there to absorb the alcohol.) Remember that each testing experiment needs four predicted outcomes, one based on each mechanism.\r\nPredict the outcome of each experiment below using all four explanations:\r\na. Hold the paper that has been dipped in alcohol between your fingers without putting it on the table while it is drying.\r\nb. Weigh the paper before the experiment, when it is wet, and then again when it is dry. [https:\/\/mediaplayer.pearsoncmg.com\/...\/sci-phys-egv2e-alg...]\r\nc. Take two identical pieces of paper and put the same amount of alcohol on each. Then, place one piece of paper under a vacuum jar and the other one just outside the jar. [https:\/\/mediaplayer.pearsoncmg.com\/...\/sci-phys-egv2e-alg...]\r\nd. Pour some alcohol into a beaker. Place a small drop of colored alcohol (alcohol to which you added some dye and stirred to mix) into the beaker with clear alcohol, but do not stir it. [https:\/\/mediaplayer.pearsoncmg.com\/...\/sci-phys-egv2e-alg...]\r\nAfter you have your predicted outcomes on a whiteboard, perform the experiments (or watch the videos of them) and decide which experimental outcomes are consistent with which predictions. Then, make judgements as to which mechanisms you have gained confidence in and which ones you can reject.\u201d Check your reasoning with the reasoning in Testing Experiment Table 12.1 on page 353 in the textbook.\r\nOALG 12.1.4 Explain\r\nThe only explanation for drying alcohol that could not be rejected by testing experiments was the explanation that alcohol consists of tiny particles (called molecules) that move randomly. How do you need to modify this explanation to account for the fact that not all of the particles leave instantly?\r\n","link":"https:\/\/www.islephysics.net\/?cat=5","name":"Facebook Posts","slug":"fbpost-archive","taxonomy":"category","parent":0,"meta":[],"_links":{"self":[{"href":"https:\/\/www.islephysics.net\/index.php?rest_route=\/wp\/v2\/categories\/5","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.islephysics.net\/index.php?rest_route=\/wp\/v2\/categories"}],"about":[{"href":"https:\/\/www.islephysics.net\/index.php?rest_route=\/wp\/v2\/taxonomies\/category"}],"wp:post_type":[{"href":"https:\/\/www.islephysics.net\/index.php?rest_route=%2Fwp%2Fv2%2Fposts&categories=5"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}