[Abstract] The theory of high school chemistry primary battery is a key point, and it is also very exploratory. In this paper, the exploration process of the primary battery is further deepened, and the mode of group inquiry is introduced. The group explores three forms of independent experiments, comparative experiments and interesting experiments, and comprehensively uses the group inquiry method to deeply teach the primary battery.
[Keywords] high school chemistry; group inquiry; primary battery
The research team is both cooperative and flexible, and can be regarded as a good learning unit. The experiments and knowledge related to the primary battery have certain complexity, and the substantial effect can be obtained by exploring in the form of a group. How to deepen the series of knowledge of primary batteries through group cooperation? The following is discussed from three aspects, sharing with peers.
I. Independent experiment, deep experience
The principle of the original battery is based on the redox reaction, which is a link that emphasizes the experimental operation. The real charm of the primary battery lies in the operation of the experiment, and the difficulty is precisely in the operation of the experiment. Teachers should actively create conditions for students, guide students to conduct experiments on their own, and experience the original battery in depth.
The most obvious phenomenon in the original battery is the discharge, so the primary battery can be used as a power source. In fact, it is often said that the battery is a function. Speaking of battery students are no strangers, often seen in daily life, and used. Most people think that the battery should be a long thick rod, or a thick round piece of iron, just connect it with "electricity", but never contact the "pool", the battery is The charged, and the water are "born with each other", how can it be associated with the "pool" of the water? It is not known that the "pool" of this battery is derived from the primary battery in which the discharge reaction occurs. In the original battery, there is a genuine "electrolysis battery", which is filled with electrolyte, and most of the life is dry battery, so it has nothing to do with the "pool". . In the simulation experiment of the primary battery, it is necessary to actually do the electrolytic battery and place the electrode. This requires a large amount of electrolyte to be configured, electrodes to be used, and various adjustments to be made. I divided the students into groups and let the group hands-on experiments and experience the process. Among them, there is a new type of hydrogen-oxygen battery experiment, which is difficult to be successful under normal circumstances. In addition, the conditions are limited and students are not good at it. The low success rate and the consumption of the electrolyte cause a large amount of waste in the experimental materials. Therefore, I led the students to reduce the difficulty of the experiment. By using a six-hole well hole experiment board, the experiment's "position is reduced" to ensure the experiment is safe and operable. Simply place the required electrolyte in a multi-purpose dropper for precise drip, and place two graphite electrodes with glass tubes to make a weak discharge reaction and successfully achieve the experimental purpose.
The experiment of the primary battery is difficult and difficult to succeed, but learning itself is a process of overcoming difficulties. The strength of a person is weak, but the power of the collective is strong. The complex galvanic battery experiment will become operational under the help of the teacher's help.
Second, multi-dimensional comparison, clear nature
The primary battery reaction is actually a redox reaction, in which the electron transfer forms a current, which is the essence of the primary battery. Therefore, in the galvanic system, the activity of the substance is an important point of exploration. The nature of the reactants in the galvanic battery is clarified through the division of labor between the groups and multivariate comparison.
One galvanic battery usually includes two electrodes, and the metal electrode is taken as an example below. Whether the electrode acts as a positive or negative electrode is closely related to activity. If an electrode is more active, it will easily lose electrons, and the valence will decrease. The reaction that occurs is called a reduction reaction. Correspondingly, if the activity of the electrode is weak, electrons are easily obtained, the valence is increased, and the reaction occurring is an oxidation reaction. To further compare the activity of the metal electrodes, I led the study group to compare the different electrode activities to arrive at a comprehensive conclusion. One of the groups compared the order of activity between the copper electrode and the iron electrode. Immerse the copper electrode and the iron electrode in the same electrolyte and connect the circuit. By observing the experimental phenomenon, it is known that the flow direction of the current outside the galvanic battery flows from the copper electrode to the iron electrode. According to the definition in physics, the current flows from the positive electrode to the negative electrode. We can conclude that the copper electrode is the positive electrode and the electron is obtained; the iron electrode is the negative electrode, and the electron is lost. The electron-and-accurate reaction occurring in the galvanic battery is as follows:
Negative electrode: Fe-2e=Fe2+ (oxidation reaction)
Positive electrode: Fe2++2e += Fe (oxidation reaction)
Passing between two electrodes In contrast, it can be judged that iron is more likely to lose electrons than copper, so activity is better. This is a comparison of a group, combined with other groups of iron-zinc, copper-zinc, copper-platinum and other comparisons, can compare the common metal activity.
Through multivariate comparison experiments, students can discover the details of the original battery and understand the concept of activity from a practical perspective. In the analysis of primary batteries, the judgment of activity is extremely important, so the comparative experiment has the effect of deepening knowledge.
Third, the use of fruit, expand the field of vision
Fruit is very common in life, so the experimental material of the fruit battery is very easy to find. The experiment of the fruit battery is still carried out on a group basis, but when the task was just put forward, the student’s reaction was still very surprising: “Can fruit still be used as a battery?” The interest of the first exploration was improved. The experiment will have the motivation to continue. First, I explained the operation method for the students. Select some sour fruits (such as lemon, pineapple, etc.) as the electrolyte in the primary battery, and select two metal electrodes with different mobility (such as copper coins and galvanized screws). Insert the electrodes into the fruit at a certain distance, so that a fruit battery is basically completed. Connect a light-emitting diode at both ends of the completed "battery" as a device for detecting current. In the experimental arrangement, I did not refine the choice of fruit, the setting of the electrode distance, and the difference between the positive and negative electrodes. These contents need to be explored by the students themselves. The student's goal is also very clear. Under the premise that the “fruit” can be used as a battery, it is necessary to explore which kind of fruit has more “electricity” and explore how the electrode can be set to generate current, and the electrode is being tested. In the group inquiry, there are those responsible for finding materials, those responsible for connecting the wires, and those responsible for recording. In short, they all perform their duties, and they have gained interest and knowledge from a small fruit battery experiment.
In high school teaching, there is not much time for students to conduct exploratory learning, so once they have the opportunity to explore, they must firmly grasp it. Group inquiry is not a form, but a practical learning method. The study of primary batteries is suitable for introducing group exploration, and it also tests the students' ability to explore.