DOUGLAS D. SMITH Gullford Hgh School Rockford, llllnols 6111 1
2) With no water present, the reaction takes longer to start, hut
produces the most steam. 3) Other things being equal:
The dehydration of sugar by sulfuric acid to produce a hot, black, expanded solid is a simple demonstration which always gets the attentions of the students. The difficult portion of the demo is the explanation. Meeks,' after finding inconsistencies in the literature, investigated the phenomena. The most amazing evidence is that, of the gases produced besides steam, much more than 50%is carbon monoxide. This led Meeks to issue the strong warning that students should not be allowed to smell the product. Other findings include:
a) the larger the volume of H20the less steam.
h) the larger the volume of sulfuric acid the larger loss to steam. 4) The temperature reaches 120 to 160T as foaming takes place. 5) Paper chromatography indicated that 5 different carhonyl compounds are formed. 6) The gases in the product include COz, Son,and CO in addition to steam.
'Meeks, Eric G., The School Science and Reuiew, 61, 215, 281
1) The quickest reaction took place in asucrose solution (10gsuerose, 7 ml water, 10 ml sulfuric acid).
Homemade Models of the Five &Atomic Orbitals Alfred E. Saieed James Madison High School Vienna, VA 22180 The nuroose of this article is to encouraee more chemistry teachers t'teach the directional character&tics of the atomic orbitals with the use of inexpensive and easily constructed models. The models have been successfully used in teaching eeneral high school chemistry, CHEM Study, Advanced i'lacemeni~hemistry,and college chemistry. Styrofoam shapes are used ru reprrsent the d-atomic orbitals. The orbital models are placed in an octahedral frame (ti corners) so that rhe x, ), and 2 axiscan be represented. An octahedron (Fig. 1) is made hy connecting I2 equal length sticks or clothes hanger wires of equal lenglh. Corner fasteners can - he ~ made ~ ~ hv cuttine a 7 cm olastic soda straw lenethwise into 2 equal pieces. Perpendicularly cross the straw pieces a t their centers and staole. You now have a olastic fastener for one corner of the octahedron. Each of the four plastic segments can be taped to different sticks with transparent tape. T o construct the orbitals you will need egg-shaped styrofoam models and a small circular piece of styrofoam. Four egg-shaped styrofoam models representing the four lobes of an orbital can be oriented on either side of an xy coordinate system by using clothes hanger wires as the axes. This is done by simply inserting the clothes hanger wire through the long axis of theegg-shaped styrofoam and tying the clothes hanger wire at the origin with string (Fig. 2). When the egg-shaped models are inserted into the octahedron alone either the xv. . zv. - . or zx axis. the result shows the orientation uf the representative models of the d , ~ . , ,d22-,, , and d,.-,. ort~itals.rc.soectivels. For exmole. Fieure 3 shows the mbdel inserted into the octahedron aiorig t i e zy axis to show the orientation of the dX2.X2orbital. Since there are only five d-atomic orbitals, point out to the students that the d,z orbital in Figure 4 may he thought of as a combination of the d,n-,z orhital and the d,n-,z orbital. T o ~
~
~~~
~
Figure 1. Octahedron model.
Figure 2. Model of the d,z~,# orbital.
Figwe 3. Model of the d,..,~ orbital inserted into octahedron to show its orientation.
Figure 4. Model of the d,z orbital inserted into the octahedron.
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This bi-monthly feature presents a potpourri of thoughts and useful items that are especially geared to high school chemistry teachers, many of which you may find of immediate use in vour classrooms. Summaries and abstracts of articles t6at have appeared recently in iournals from around the world are also included. Send ;our contributions to the feature editor.
Volume 57, Number 11, November 1980 1 805
construct the d,z orbital, two egg-shaped styrofoam models are oriented on either side of the circular piece of stvrofoam. Theseare held tugether hy arlothes hsngerwirethrmxh the center.'l'his model is then inserted alonn.rhez axisut'rhe uctahedron as shown in Figure 4. The lone model which is used to represent the dxS,dy,, and d,, orbitals is constructed by using the clothes hanger wire as the axes and by lining up four egg-shaped styrofoam models in between the x and y axes. These are held together by sticks glued inside the lobes and tied with string to the origin. I recommend using only styrofoam glue since it does not dissolve styrofoam. When the styrofoam model is inserted into the octahedron alone either the xv. ...v z.. or x z axis. it shows the representative models of the d,,dyz, and d,, orhitals. Figure 5 shows the orientation of the d,, orbital. By using these models, the students clearly see that the five d-atomic orbitals consist of two d-atomic orbitals (the d,z and d,%,z orbitals) which have lobes pointing toward the corners of an octahedron and three d-atomic orbitals (the d,,, d,, and d,,) which have lobes lying between the corners of the octahedron. For an edge length of 25.4 cm, a 10.3 cm long styrofoam egg
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806 / Journal of Chemical Education
Figure 5. Model of the d, orbital inserted into the octahedron.
is used with a 38 cm wire which goes through the models to indicate the x , y, and z axis. Editor's Notes (1) Stvrofoam e. m. s are usuallv available in craft and hobbv
shops.
(2) Styrofoamcan be painted with tempera paint if a few drops of detergent are added to the paint. Other paints may dissolve
the model.
