A knowledge of simple physical chemistry is now required for all chemistry examinations, candidates for which are expected to have a working acquaintance with simple physical apparatus, to be familiar with the barometer and thermometer, the effects of heat on solids, liquids and gases, density and specific heat, etc., etc.; they are liable moreover to be asked to solve any simple problems on measurement. Now by giving precedence to “physical” chemistry, all this is done and done thoroughly before examinations are thought of, so that what is generally regarded by pupils at the present time as the most difficult portion of their subject is made by this means its A B C, and the time spent upon actual examination work can be considerably curtailed.
“Pure” chemistry is introduced by the study of the methods of testing all kinds of substances so as to be able to classify them roughly as mineral or vegetable, organic or inorganic, etc. The chemistry course suggested by Dr. Armstrong and adopted by the Incorporated Association of Head Masters is strongly to be recommended, as it is drawn up particularly with a view to imparting “not only information but chiefly a knowledge of method”. It opens with “studies of the effect of heat on things in general; of their behaviour when burnt,” and goes on to the investigation of such familiar things as air and nitrogen, combustion and oxygen, hydrogen and water. Formulæ and equations are rigidly excluded, the aim being to give a broad introduction to the subject; on the other hand quantitative experiments form a much larger part of the curriculum than is usually the case, the previous training in physical methods having prepared the way for teaching chemistry in a more exact manner than is generally possible with beginners.
A girl who has gone through the scientific training outlined in the preceding pages will possess an elementary knowledge of many subjects; she will find little difficulty in mastering the information required for the London Matriculation or any other preliminary examination in physical science, the greater portion of the ground both in physics and chemistry having already been covered during the preliminary course indicated. It is certain that students who have undergone such a systematic education without hurry and without pressure, and with opportunities for reasoning out each step for themselves, will be in a condition to derive the maximum of benefit from subsequent instruction not only in chemistry but in all other branches of knowledge.
Typical Lessons in Chemistry.
At the beginning of the lesson the problem to be solved is announced by the teacher, who invites suggestions as to how it should be attacked. A scheme of work is thus prepared which is carried into practice by the pupils; every detail of manipulation is performed by the girls themselves, who select their own apparatus, bend their own tubing, etc., referring only occasionally to the teacher for help. The scheme is elaborated as the investigation proceeds so as to form a piece of consecutive reasoning which may extend over a series of lessons.
Problem. To discover the constitution of chalk.
Typical lesson.Being familiar with simple methods of testing unknown substances, heat and the action of acid are at once suggested by the pupils as a means of investigation, and a preliminary examination is made showing that heat does alter chalk in some way, whereas the addition of acid causes the liberation of a gas. The next step is to find out whether the chalk loses or gains anything by being heated; also to determine the nature of the gas given off under the influence of acid.
Suggestions are again received from the girls, who are led to decide that the first part of the question may be answered by submitting a weighed quantity of chalk to a moderately high temperature, weighing at intervals until the weight, if it changes at all, again becomes constant.
They proceed therefore to weigh their empty crucibles with the usual precautions and then to reweigh them after having put in some dry chalk. The numbers obtained are carefully entered in the laboratory note-book with which each girl is provided. The crucibles are then placed in a “muffle” furnace, which the pupils are taught to manage for themselves, and are only withdrawn at the end of the lesson and placed in desiccators to be reweighed at the beginning of the next lesson, when they will be again submitted to the same treatment until the weight is constant.
While the crucibles are being heated preparations are made for finding out the action of acid on chalk; the pupils are led to suggest a simple form of apparatus for measuring the volume and weight of the gas given off, and hence for determining its density. By the time this is done the hour and a half allowed for the lesson will probably have expired. At the next lesson, after a preliminary questioning as to what each pupil has done and is going to do, the apparatus decided upon at the previous lesson is carefully prepared; subsequently the actual experiments to determine the quantity of gas given off are performed and its density determined, and finally it is shown that the gas given off from chalk under the action of heat is identical with that released by acid, chalk being composed of this gas and the residue left after heating it in a muffle furnace until the weight is constant.