TEACHING HIGH-SCHOOL CHEMISTRY TEACHERS
A n actual workable outline on the subjects of valence and the writing of formulas and equations i s herewith presented to aid beginning chemistry teachers.
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Occasionally a high-school graduate who has entered a college chemistry course, comes back and tells his high-school instructor, with some degree of satisfaction, that the college instructor told the students to forget all their high-school chemistry before attempting to start their college work. The high-school teacher has heard this often enough to be able to keep quite unperturbed. He agrees, and tells his former disciple to adopt without question the ways of the new master. There are certainly essential differences in methods of presentation in secondary-school and college chemistry. The difference in the subject matter necessitates them. Few modern high schools teach college-preparatory chemistry exclusively. There are too many household, civic, and industrial applications that demand attention. Chemical theory is not the thing of primary interest to large numbers of present-day secondaryschool students. Yet valence must be taught, and equations must be balanced, and problems must be solved. Now, what does the college graduate, who starts his practice teaching in high-school chemistry, do? Is he able to start a t the level of the highschool child? Seldom. That college graduate has to forget much of his college chemistry if he is to be a successful high-school teacher. Few graduates are able to tackle adequately the problem of teaching valence, formula writing, and equation balancing for the first few years. To aid them, the writer prepared the following outline, for what it may be worth, either to beginning high-school teachers, or to those who face the problem of teaching practice teachers. The new teacher could have enough copies of this outline mimeographed to give every pupil one. I. How are acids end salts named? No. of Name For Salt derived elements: includes: Ends in: example: from this acid: Kind of acid: (A) Binary ..................................................... (B) Ternary . . . . . . . . . . . . . . . . . . . . (I).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (If one less 0 atom:) I I . What are the walences qf imporlnnt elemenls and radicals? (A) Those having valence of +I: (B) Those with valence of -1: Name: Symbol: Name: Symbol: (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
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(4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (5). . . . . . . . . . . . . . . . . . . . . . . . . . . . . (6).. . . . . . . . . . . . . . (ous) . . . . . . . . . . (7). . . . . . . . . . . . . ..(om) . . . . . . . . . . (C) Those having valence of +3: (1). . . . . . . . . . . . . . .(ic) . .......... (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (E) Most metals used in high-school chemistry that are not listed above, have valencc of +2.
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(4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (5). . . . a t e , and.. ... i t e . . . . . . . . . . . (6). . . . . . . . . . . . . . . . . . . . . . CIO. (7). . . . . . . . . . . . . . . . . . . . . . C2Hs02 (D) Those with valence of -3: (1). . . . . . . . . . . . . . . . ..ate. . .......... (2) . . . . . . . . . . . . . . . . . . ite. . . . . . . . . . . (F) Most non-metals and acid radicals used in high-school chemistry, not listed above, have valence of -2.
III. How are formulns of chemical compozmds writlen? For example, using the followingrules, and applying what you know about valences, write formulas for: Silver Sodium Aluminum hydroxide: Rules: nitrate: sulfate: (I) Determine the valence of metal, .............................. (2) Determine the valence of non-metal, -: .............................. and - same, or not? .............................. (3) Are valences of (4) If same, write symbol of each, once: .............................. (5) If not same, take each element or radical as many timesas thevalence of the olher one: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ti) If a radical (compound) is taken mare than once, put parentheses ( ) around it, .............................. and write number outside: If you think you know how t o write formulas, fill these in: Chloride Hydroxide Sulfate Carbonate Phosphate (1) . . . . ( 2 ) . . . 3 . . . (4) . . . . . . . . . .(5) . . . . . . Sodium Ammonium (6) . . . . . . . .(7) . . . . . . . (8) . . . .(9) . . . . . . . . . (10). . . . . Calcium (11). . . . . . . .(12). . . . . . . .(13). . . . . . . .(14). . . . ( I ) . . . . . Barium (16). . . . (17). . . . ( 8 ) . . . . .(19). . . . . . . . . (29). . ..... Aluminum (21). . . . . (22). . . . (23). . . . (24). . . . . . . . . .(25). . . . . . Allowing 4 points for each correct one:. . . . . . %.
+:
+
IV. Four chief types of chemical reactions are: (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . as.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . as: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (a) A metal displaces another in a compound, if the element by itself is higher in the electrochemical series than the element in the compound is. As:. . . . . . . . . . . . . . (b) A uon-metal displaces another in a compound, if i t is above that othcr one in the following series: Chlorine Bromine Iodine As: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (4). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..which . go t o completion due to: (a).. . . . . . . . . . . . . . . . . . . . . . . . . . . ..as:. . ..................................... (b). . . . . . . . . . . . . . . . . . . . . . . . . . . . .as:. .. ..................................... and ( c ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..as:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
V. Whal is neulralimlion? An acid, which always starts with.. react t o yield. .... and a , . as:
...
. ., plus
a base, which always ends with. . . .
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JOURNAL OF CHEMICAL EDUCATION
M ~ n c a 1W31 ,
VI. Whet are the solubility rules? With reference to water: (1) All. . . . . . . . . . . . , . . . . . . . . . . . . .and. . . . . . . . . . ..compounds are soluble. (2) All. . . . . . . . . . . s, . . . . . . . . . . . s, and . . . . . . . . . . s. are soluble. (3) All chlorides are soluble, except:. . . . . . . . . . . ., . . . . . . . . . . ..and. . . . . . . . . . . . (1) All sulfates are soluble, except:. . . . . . . . . . . ., . . . . . . . . . . . .and............ (5) . . . . . . . . . ..s, . . . . . . . . . . . s and. . . . . . . . . . .s are generally insoluble, except:
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