1 Chemistry Manipulatives for Middle School Students Lynn A. Melton University of Texas at Dallas CAST November 6, 2008

2 Website The concepts are presented in greater detail. PowerPoint presentations can be downloaded.

3 Fundamental Concepts of Chemistry 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 Atoms Digression 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 Atoms Seeing 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 Atoms Seeing 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 Atoms Seeing 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 Atoms Seeing 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 Atoms Seeing 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 Atoms Seeing Without Seeing Now, the whole group discusses their results. This is our version of an international scientific meeting.

16 Atoms Seeing Without Seeing Hands On Time! Go to it!

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

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

19 Atoms Seeing Without Seeing On Planet Xanadu, is there a periodic table?

20 Atoms Seeing 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 Atoms What 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 Atoms What data do we have? Atomic Force Microscopy (neat websites) c_resolution_on_si_111_7x7_in_non_contact_mo de_afm/~Omicron

23 Atoms What AFM data do we have? Silicon surface

24 Atoms What AFM data do we have? NaCl (salt) surface

25 Atoms What AFM data do we have? Conclusion: –The world “feels” granular.

26 Atoms What 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 Atoms What MS data do we have? Mass Spectrometry separates atoms (actually ions) according to their differing masses. Neat websites! html/examples.html ments.html

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

29 Atoms AFM 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 Atoms Making 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? 8 th 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?