VOL. 3, No. 10
WATERAS THE BASISPOR
A
STUDY OF CHEMISTRY
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WATER AS THE BASIS FOR A STUDY OF CHEMISTRY MARYLoursE FOSTER, SMITH COLLEGE, NORTHAMPTON, MASS. In offeringstill another method for the study of chemistry, the author is presenting no new material, merely a new form of approach. Any study of chemistry today must be based on the quantitative method; and since all chemical reactions depend upon physical conditions of temperature, solution and quantity, a good deal of whatis called physical chemistry must be early introduced to the student in order that he may use these relations and conditions to promote chemical reactions. Thus i t is hoped that the student will get more definite understanding of the inter-relation of phenomena and hence a conception of what the word science connotes, i. e., organized knowledge in its quantitative relation. Modern chemistry with all its recent advances is based largely upon the theories of solution, i. e., upon the relation of substances to water. Water, too, in its various physical forms is familiar matter. Lavoisier said that Nature accomplished manifold phenomena largely through the agency of water and that it was well for us to try and penetrate her secrets by a study of the phenomena in which water is concerned. The scheme here presented in outline is offeredas a basis for both laboratory and recitation work. The latter should combine both the "quiz" on the review and a discussion of topics which the student has looked up for himself. This is the basis of the "project" method and certainly arouses the interest of the student and develops ability and confidence in his work as no other method does. The theory and the fact found by experimentation in the laboratory can be widely applied and interpreted. The three should always be woven together in concrete form in a written paper to be read in class. The author has used this method with her students. They report that they have found it stimulating and effective. A.
Physical Properties
1. Differentforms in which water appears, states of matter (a) Solid-Ice 1. Determine the temperature of some bits. of ice in a beaker . . with a Centigrade thermometer; heat very gently, stirring with the thermometer and watching the temperat;re indicated on the thermometer; latent heat of liquefaction 2. Study the effect of adding c'ommon salt to ice. A t once the student begins to learn quantitative relations and the use of the balance and of Centigrade thermometer.
(b) Liquid 1. Determine the boiling point of water on a centigrade thermometer
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oa CHEMICAL EDUCARON
Ocros&a.1926
Mfect of decreased pressure on boiling point. experiment 3. Determine latent heat of vaporization. 2.
Franklin's
Vapor or Steam 1. Pressure of water vapor, Dalton's experiment; phenomena of condensation and evaporation; effects on climate, etc. 2. Density (a) Determine specific gravity of various substances (b) Use of hydrometer on liquids, salt solutions, etc. (c)
3. Solvent Power (a) Soluble substances 1. Common salt 2. Saltpeter 3. Copper sulfate 4. Dissolve in 10 cc. of water small portions of above salts until saturated; evaporate a portion; set another aside to crystallize. Heat a crystal of copper sulfate to drive off moisture, weigh, dissolve in least amount of water and allow to crystallize; remove the crystals, dry, and again weigh. Phenomena of evaporation, crystallization, water of crystallization.
B.
(b)
Insoluble substances 1. Plaster of Paris 2. Chalk 3. Sand 4. Lime 5. Add water to small portions of above solids, filter, distil, evaporate 6. Hard and soft waters; test with soap solution; phenomena of filtration, distillation; applications to daily life.
(c)
Colloidal solutions 1. Study inorganic suspensions 2. Study organic gels and emulsions, egg white, gelatin, starch.
Chemical Properties 1. Electrolysis, proof of composition, significance of symbols, definite proportions, analysis, elements, compounds, ancient doctrine, modern theory developed by Lavoisier, conservation of matter 2. Study of the constituents of water
(4
Oxygen 1. Test HgO, Pb30a, KC103
+
2. Preparation on a larger scale, KC103 MnOz;test for properties; catalysis 3. Prepare CuO, P20s, SOz; oxidation; test solubility and reaction of solution to litmus and other indicatorsacid 4. Burn C in oxygen and in air; test products-respiration 5 . Mg steam; perform qualitatively 6. Prepare MgO quantitatively.
+
(b)
Hydrogen 1. Zn HC1; preparation and tests 2. CuO Hz;reduction, synthesis, Priestley, Cavendish 3. A1 HCl. Use about 140mg. of wire and 200 cc. HC1, 1:5, in a graduated cylinder, inverted in a beaker of water. Read volume of gas, correct, and calculate the hydrogen equivalent. Phenomena of some gases, laws of gases, Boyle and Charles.
+
+
+
C. Acids 1. Sulfuric acid; burn sulfur in air, add water and aerate; properties H8Oa NaCI -+ HCl; test with Zn, Fe; properties of hydrogen chloride; repeat B2, b3 using Mg instead of Al; Law of Definite Proportions-Atomic Weights 3. HzSOa KN03 --+ HN03; test with Zn and Cu; properties 4. Vinegar; determine strength by means of normal solutions; use of indicators; make distinction between strong and weak acids; hydrogen ion.
+
2.
+
D. Salts 1. HC1
+ NaOH; tleutralization; prepare other salts.
E. Modern Theory of Solution 1. Behavior of current passing through some substances both dry and wet; use lamp to show when current passes 2. Electrolysis of AgN03 or CuSOa; nomenclature, ion, cation, anion, cathode, anode; chemical equivalent is the electrical unit of matter Faraday 3. Ionic hypothesis.
(a) Conductivity of solutions
( b ) Strong and weak acids and bases; relative strengths; solubility law (c)
Replacement 1. CuSOa Fe; AgN03
+
+ Mg; Zn + Pb(CzHs02); Fe, Zn, Cu
on AgNOx; F'e, Mg, Cu on Pb(N03)s,etc.; electromotive series; periodic table 2. Study electrolytic deposition of metals.
F. Qualitative and Quantitative Analysis 1. Group of alkali metals and alkaline earths, Na+, K+, NH4+, Mg++, Ca++, Sr++, Ba++
(a) Qualitative analysis 1. Characteristic tests based on physical properties, flame, spectrum, and solubilities; chemical equilibrium, the writing of ionic reactions 2. Separation of very simple unknown mixtures. (b) Quantitative determination of CaCls 2. Aluminum and zinc groups, Fe+++, Al+++, Cr+++, Ni++, Co++, Fe++, Mn++, Zn++ (a) Qualitative tests and analysis 1. Characteristic tests, individual and collective. 2. Amphoteric nature of these hydroxides; periodic table, hydrolysis of salts, oxidation and reduction. (b) Quantitative determination of Fe+++in F'e2(S0& (c) Metallurgy and mining. 3. Copper and Silver groups, Ag+, Hg+, Pb++, Hg+t, Pb++++,Bi+++, Cu++, Cd++, As+++, As+++++,Sb+++, Sb+++++,fjn++,Sn++++,
(a) Qualitative tests and analyses; analyses of silver coin (b) Quantitative determination of Ag+ in silver coin 4. Brief study of the most important acid radicals 5. Radio-active substances, helium and radium 6. New theory of atomic structure. G. Organic Compounds. 1. Composition and structure 2. Study of the two important groups, the aliphatic and aromatic series, with especial emphasis on substances related to foods and industries.
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The %*t q d , greatest glory of an iuvestig?t~rishis truthfulness and conscientious.. ness; all a s &
