The Amazing Mole. Program Support Notes. Senior Secondary. 26mins. Chemistry. Bringing Learning to Life. Video Education Australasia

Transcription

1 Video Education Australasia Bringing Learning to Life Program Support Notes Senior Secondary The Amazing Mole 26mins Teacher Notes by Richard Leigh B.Sc. Dip.Ed. Grad.Dip Film & TV. Produced by Video Education Australasia Commissioning Editor Christine Henderson B.Sc. Ph.D. Dip.Ed. Executive Producer Mark McAuliffe Dip.Art (Film & TV), Dip.Ed. B.Ed. Ph.D. Video Education Australasia Pty. Ltd. Suitable for: Chemistry To order or inquire please contact VEA: Australia 111A, Mitchell Street, Bendigo, Victoria 3550 FREECALL: Phone: (03) Facsimile: (03) New Zealand PO BOX 4390, Shortland St., Auckland FREECALL: Facsimile: Website WARNING The Copyright proprietor has licensed the motion picture contained on this video cassette for non-theatrical use only and prohibits any other use, copying, reproduction or performance in public, in whole or part. The penalties for unauthorised copying of this program include a $50,000 fine for individuals and a $250,000 fine for institutions. These notes can be freely copied for classroom use only.

2 For Teachers: Brief Summary of Program The discovery of the mole and its relationships to mass, volume, concentration and number of particles absolutely revolutionised science in its day, rather like the unravelling of the human genom e is doing today. This program introduces students to this fundamental concept in chemistry. With stunning graphics and visual metaphors, our young presenter, Brad, explains the mole concept in a step-by-step approach: the scale of atomic particles Avogadro s number moles in reactions molar mass mole formulae standard temperature and pressure All the essential mole formulae are introduced and any students struggling to remember every formula can find solace in Brad s closing song, The Mole Formula Blues. Complete with quizzes and summaries. Further Areas to Consider The mole concept lies at the heart of the branch of chemistry known as stoichiometry. Stoichiometry is the accounting of chemistry, and while the fundamentals are quite simple, students often have trouble coming to grips with the topic when it is first introduced. With this in mind, this program aims to be an accessible introduction to the mole concept. The program is logically divided into chapters with opportunities to stop the tape throughout in order to review and exercise any new knowledge. In the section marked For Students, questions have been kept to a minimum to encourage students to focus on the program. One viewing strategy is to play one chapter at a time as follows: 1. stop the tape prior to each summary section 2. have students complete the key concepts (and any formulae), and 3. play the summary section 4. clarify key points raised 5. continue with next chapter of program. One simple extension question is provided under Activities After Viewing, but students should be encouraged to practise the new knowledge with a range of different examples using various combinations of mole formulae. The order in which a difficult concept is introduced varies from one text book or educational resource to another. The detailed explanation of program (following Timeline, below) describes how this program sequences the subject matter. Other Relevant Programs available from VEA The Super-Charged World of Chemistry Series Chemistry 1 & 2 Issues in Chemistry Chemical Analysis 1 The Elements of Matter Please visit our website for many more relevant programs 2

3 Program Timeline 0:00 Warning, VEA opening and title 0:55 Program start daydreaming at the trainset: the scale of things 1:45 The Mole is a Big Big Number! What is a mole? 2:25 Marshmallows filling the earth (20km deep!) 4:20 Summary 4:45 The Amazing Mole How it s useful 6:20 The Marshmallathon (F 2 C 12 O 8 ) 7:20 STOP TAPE: Example for students 8:20 Formula 1: no. of particles = n x 6.02 x :20 Summary 9:50 Moles In Reactions Proportions of atoms in equations 11:25 STOP TAPE: Example for students (H 2 O) 11:50 Solution 12:20 Summary 12:40 Mole Detectors Mass of atoms 14:05 Why 6.02 x 10 23? 15:15 Molar mass 15:30 Formula 2: n = m / M R 16:10 WORKED EXAMPLE: no. moles in 36g of H 2 O 16:40 Summary 17:25 Moles In Every State Solids, liquids, gases 18:35 Formula 3: n = CV 19:20 Temperature, pressure, volume 19:50 Formula 4: PV = nrt 20:45 Standard Temperature & Pressure 21:50 Standard Lab Conditions 22:30 Summary 23:35 Review: The Mole Formula Blues Light relief! 24:05 Summary (all formulae listed in program) 26:00 Credits & end 3

4 Detailed explanation of program The Amazing Mole Introduction We first meet Brad daydreaming about the scale of things as he looks over his kid brother s model train-set. He imagines himself as a tiny person, small enough to count the model rocks on the side of the track. This is an introduction to the idea that when we are counting tiny particles (like atoms and molecules) we are dealing with enormous numbers. Chapter heading: The Mole is a Big Big Number! What is a mole? Quite simply, a mole is a unit of measurement, says Brad, as he gathers eggs to make up a dozen. A mole is just like a dozen. But while a dozen represents 12, a mole represents 6.02 x To illustrate just how big this quantity is, Brad places marshmallows on the ground and covering an area the size of an oval and beyond so beyond that the camera pulls out to reveal a world covered in marshmallows 20km deep THAT S how many marshmallows there are in a mole. It s known as: Avagadro s number. Chapter heading: The Amazing Mole Viewers are introduced to the idea of what a mole is useful for quantifying amount of substance in reactions, among other things. A fictitious molecule, the Marshmallathon is introduced (F 2 C 12 O 8 ). Coloured table-tennis (ping-pong) balls in a box replace the marshmallows Brad laid out across the world, and by simple arithmetic, he calculates his first mole formula: no. of particles = n x 6.02 x Students are encouraged to try this calculation before the answer is given. An important point is made by an off-the-wall comic-strip: n represents the number of moles. Chapter heading: Moles in Reactions Lots of scientists had realised that only a set amount of hydrogen gas would react with a set amount of oxygen. Now they could see that it was in groups of moles! Brad uses the example of: 2H2 + O2 2H 2O He writes the equation in the night sky (illustrating its enormity) and explains that 2 moles of Hydrogen molecules would always react with 1 mole of oxygen molecules and produce 2 moles of water molecules. It s just like a big scaling up of 2 molecules of Hydrogen plus 1 molecule of oxygen produces 2 molecules of water. He says. Students are encouraged to solve this question: If half a mole of hydrogen reacts with oxygen to produce water, how many moles of oxygen will be needed? And how many moles of water will be produced? Chapter heading: Mole Detectors The idea of mole detectors is an off-beat way of getting students to think about how substances can be quantified. Brad himself is surprised to discover that the first mole detector is actually a kitchen scale. How do we measure mass when the particles we re dealing with are so small? Scientists use a relative scale. With a traditional set of balancing scales, Brad weighs the table-tennis ball called carbon 12 against fluorine 19 and then against oxygen 16. The relative scale defines carbon as 12 (atomic mass) units heavy, while fluorine and oxygen are 19 and 16 respectively. The question is posed: Why is Avogadro s number such a strange quantity? The answer is that this number is exactly the number of particles found (experimentally over the years) in carbon 12. The relationship between mass and (relative) molar mass is made here, and the following formula introduced: n = m / M R Brad works through the following example: What s the amount of substance in 36g of H 2 O? 4

5 Notes: 1. This chapter of the video is key to the understanding of the mole concept. Students should be encouraged to consolidate this knowledge by discussion and questioning at this stage before going on. Many courses in fact introduce the remaining content of this program at a later stage. 2. Throughout the program, M R is used in reference to molar mass. For compounds consisting of molecules, the molar mass, (M) is numerically equal to the relative molecular mass (M R) expressed in grams per mole. Chapter heading: Mole Detectors Following the theme in the previous chapter, Brad talks about other ways of detecting moles, that is, measuring the amount of substance in different states: solids, liquids and gases. Having already dealt with solids, he moves onto liquids. The formula: n = CV is given an a simple example worked through on screen. What s a bit more tricky about gases is working out how to measure it, says Brad as he tries to pour some wafty, coloured shape onto his balancing scales. Gas, as he goes onto say, is affected by three variables: temperature, pressure and volume. The formula that relates all these is: PV = nrt This is simplified algebraically by making temperature and pressure a known or fixed value. Standard Temperature & Pressure and Standard Lab Conditions are the values scientists have chosen for simplicity. The volume of one mole of gas under each of these conditions is then given. Chapter heading: The Mole Formula Blues In addition to the summaries at the end of each chapter, this part of the program attempts to connect with students again by implying, if you think there s been a lot of formulae to remember in this program you re not alone! Even our young presenter, Brad, has trouble! Brad launches into a blues piece as he wanders around the model train-set where we first met him. A final summary covers all formulae introduced throughout the program. Useful Related Websites *At the time of printing these Teacher Notes, these websites were found, after a number of separate visits, to be both accessible and appropriate for the subject material. Teachers are advised to thoroughly check any website listed here before passing its details on to students (click 'moles' link for definition) (ditto above) (and again) 5

6 For Students: Activities While Viewing Take notes! Use the following space to complete the essential points that come up in the program. Under each chapter heading note key concepts and the formulae introduced. Introduction / opening The Mole is a Big Big Number! Avogadro s number is: The Amazing Mole Formula: n stands for: Moles in Reactions 6

7 Question asked: If half a mole of hydrogen reacts with oxygen to produce water, how many moles of oxygen will be needed? And how many moles of water will be produced? Mole Detectors Formula: Question asked: What s the amount of substance in 36g of H 2 O? Mole Detectors Formulae: 7

8 Activities after Viewing Extension Question: Imagine you own a cosmetic company. You need to buy in expensive perfume to put into your products. You don t want to have spare perfume sitting around unused it will vaporise after all so you only buy it as you need it. You must be able to calculate how much you need for a particular reaction needed to make face cream. However your measuring cylinders were all broken in a storm last night so you can t measure out precisely the mole (in terms of volume) that you need for each reaction. How can you get the required order done by the end of the day? The perfume comes in bottles of 0.5 Litre only. Its concentration is 2.3 moles per Litre. So calculate how many moles per bottle. 8

9 Solution to extension question: N = c v so moles = 2.3 x 0.5 = 1.15 moles per bottle The Amazing Mole You check the label and the particular perfume has a molecular mass of 84, so you can calculate how many grams of perfume must be in each bottle using the mass formula. N = m/m for 1.15 moles, 1.15 = m/84 so mass of perfume per bottle = 96.6grams. So 1.15moles = 96.6 grams Therefore moles would weigh: 96.6 x /1.15 = 0.294g for each reaction needed. Luckily your mass scales are still working after the storm! 9