Chemistry Manipulatives for Middle School Students

1. Chemistry Manipulativesfor Middle School Students Lynn A. Melton University of Texas at Dallas melton@utdallas.edu CAST November 6, 2008

2. Website • http://www.chemchapterzero.com • The concepts are presented in greater detail. • PowerPoint presentations can be downloaded.

3. Fundamental Concepts ofChemistry • Atoms • Bonding/Molecules/Reactions • Structure/Properties • Activity of molecule derives from its structure

4. Atoms: Key Question • If a sassy eighth grader asked you “So why – other than you and the book say so – should I accept that every material in the world is made up of atoms? After all, I cannot see atoms.” • Your answer ….

5. Atoms: Key Question • Your answer …. • Define an atom carefully • Data #1:Atomic Force Microscopy (the world is granular) • Data #2: Mass Spectrometry (the particles have different weights) • Work on “Seeing Without Seeing”

6. Atoms • Definition of an atom (a la Melton) • Rip any piece of the world apart, but you may use only the energies available to the ancients – horses, flames, and lightning. When you cannot rip the smaller pieces apart any longer [to produce only neutral particles] then those last [neutral] particles are ATOMS.

7. AtomsDigression • Words that may come up. (If they don’t ask, don’t bring them up; Keep to the simple model) • Electron, proton, neutron: subatomic particles, they will be discussed as more complex MODELS • Element: a group of atoms all of which have the same number of protons • Ion: a atom in which the number of electrons is not the same as the number of protons • Isotopes: atoms that have the same number of protons but different numbers of neutrons

8. Atoms: The Concept • The weight of anything in the world is the same, regardless of how finely you divide it. • Or, when you add up the weight of all the pieces, you get the weight of the original thing. • The world is granular; it is • Sand rather than shampoo • Grapes rather than jello • Every material in the world is built from atoms.

9. Let’s Work with Atoms • This hands-on exercise is part of a series of lessons, all designed to help students accept that atoms are real. • Since, atoms are too small for us to see with our eyes, let’s work on Seeing Without Seeing.

10. AtomsSeeing Without Seeing • What do we need to know about atoms? • What is your weight? • What can I build with you? (or, What other atoms can you bond to?)

11. AtomsSeeing Without Seeing • Each team must have an A and a B • A is the person with the gaudiest clothing • In this exercise, A is the “doer” and B is the “recorder”. • A may not write • B may not touch. • We will switch roles later.

12. AtomsSeeing Without Seeing • A space probe has just returned from Planet Xanadu with samples of material. • Your assignment is to go into the laboratory and find out whether the samples display the same chemistry that we observe on earth. • In particular, on Planet Xanadu, is there a periodic table?

13. AtomsSeeing Without Seeing • The garbage bag is your laboratory. It contains material from Planet Xanadu. • One person inserts both hands into the garbage bag and does the research. The other person records the results. • Please do not peek. At the right time, I will tell you when to look.

14. AtomsSeeing Without Seeing • Carry out your research, write up the results, and make sure that A and B agree on what has been written. • Switch bags with adjacent team. • Check the results of the other team, but now A is the “recorder” and B is the “doer”.

15. AtomsSeeing Without Seeing • Now, the whole group discusses their results. • This is our version of an international scientific meeting.

16. AtomsSeeing Without Seeing • Hands On Time! • Go to it!

17. AtomsSeeing Without Seeing • Switch bags with another team. • Each team analyzes the other sample.

18. AtomsSeeing Without Seeing • Now, all together, let’s discuss the results.

19. AtomsSeeing Without Seeing • On Planet Xanadu, is there a periodic table?

20. AtomsSeeing Without Seeing • Now, look at the atoms. • What do we see with our eyes? • Why are the atoms made the way they are? • Color? • Shape? • Weight? • Bonding?

21. AtomsWhat data do we have? • Atomic Force Microscopy • A very sensitive probe is scanned across the surface, and the force on the probe is measured • By using electronics to keep the force constant, we can – line by line – generate a profile of the surface • The best instruments can “feel” individual atoms. • Conclusion: the world is granular.

22. AtomsWhat data do we have? • Atomic Force Microscopy (neat websites) • http://www.mee-inc.com/afm.html • http://www.rhk-tech.com/hall/NaCl-mica.html • http://stm2.nrl.navy.mil/how-afm/how-afm.html • http://www.omicron.de/index2.html?/results/atomic_resolution_on_si_111_7x7_in_non_contact_mode_afm/~Omicron

23. AtomsWhat AFM data do we have? Silicon surface

24. AtomsWhat AFM data do we have? NaCl (salt) surface

25. AtomsWhat AFM data do we have? • Conclusion: • The world “feels” granular.

26. AtomsWhat MS data do we have? • Mass Spectrometry separates atoms (actually ions) according to their differing masses. • Different masses have different trajectories! • Real mass spectrometers require a very good vacuum, and they are expensive.

27. AtomsWhat MS data do we have? • Mass Spectrometry separates atoms (actually ions) according to their differing masses. • Neat websites! • http://www.chem.arizona.edu/massspec/example_html/examples.html • http://www.cea.com/cai/simstheo/mspectra.htm • http://www.chemguide.co.uk/analysis/masspec/elements.html

28. AtomsWhat MS data do we have? The different elements have different masses.

29. AtomsAFM and MS • AFM – The AFM box allows students to mimic the measurements made with a real AFM. Maybe you can feel individual atoms? • MS – The mass spectrometer allows students to mimic the measurements made with a real mass spectrometer. Do you want to see the trajectories of your atoms?

30. AtomsMaking Stuff • What does it cost? • Atoms -- average cost is about $0.10 per atom (steel core costs $0.08 per atom) • AFM -- $2-5 (most of the cost is velcro) • MS -- $2

31. Should I use this approach in my class? • It (probably) will help students with the fundamental concepts of chemistry. • Perhaps you are constrained by the sequencing of chemistry instruction?

32. Should I use this approach in my class? • Perhaps you are constrained by the sequencing of chemistry instruction? • 8th grade ??? [pre-AP chemistry  AP chemistry  Freshman Chemistry  degree in chemistry]

33. Should I use this approach in my class? • It (probably) will help students with the fundamental concepts of chemistry. • Perhaps you are constrained by TEKS and TAKS?

34. Should I use this approach in my class? • Perhaps you are constrained by TEKS and TAKS? • “Which letter in this model of a boron atom represents a neutron?” (TAKS grade 8 science April 2006)

35. Comments • Lots of ideas there • It you use this material in the classroom, it may take you a month or more to work through the material. • The “hands on” stuff will count as labs. • No algebra! No exponents!

36. What can we do together? • Longer workshops on this theme? • Get 10 teachers together and ask me • Atoms (and how to make a set)? Density? Gases and Pressure? • Course at UTD “Lab and Demonstrations for Middle School” -- Spring 2009 • Research/publication on the effectiveness of this approach?