Instructors (teachers, parents or related persons) provide guiding clues for students to find and ask questions by setting topic situations, which is also called setting up "problem fields". This is the most urgent introductory guidance for students in the topic selection of research-based learning.
For example, show a dying fish, or several students discuss the dialogue about "dying fish", or read newspaper materials about polluted rivers, and ask students to ask the question "Why the fish in rivers are dying (or extinct) and the countermeasures".
For another example, in the innovative design and innovation course of the labor technology course in the middle school attached to the National People's Congress, the teacher always provides some materials and essentials for making award-winning inventions, asking students to find new problems on the basis of imitating scientific and technological production, and then put forward their own new invention project design topics.
For another example, I once commented on a case in which Cai Ying, a student of Hubei Wuchang Experimental Middle School, transplanted the principle of capillary amplification into his own invention design project "Chua's solid density bottle" and achieved success in one fell swoop. After studying and thinking about this case, I asked the students to discuss how to find and put forward problems, how to design inventions, how to understand the main points of comments, how to put forward suggestions for improvement, and how to relay inventions (for example, using the principles of capillary amplification, such as optical path amplification, lever amplification and circuit amplification, can solve some long-standing problems we found. These questions can be raised by students alone, through discussion, and finally even by teachers for students to choose freely. In my opinion, this is also the most effective way to provide students with the background of topic selection and facilitate students to find and ask questions.
Attached is the case of "Chua's solid density bottle":
1. Name of work Chua's solid density bottle
2. Author's school and name: Cai Ying, Wuchang Experimental Middle School, Hubei Province.
3. Tutor Zhou Qinglin
4. The 7th National Youth Invention Gold Award
5. Introduction to the work
At present, gold ornaments are becoming more and more popular, and the requirements for detecting their gold content are becoming more and more common. It is too expensive to use high-precision instruments to make atomic spectra.
Once, the author happened to browse the Lee's solid pycnometer on page 106 of Glass Instrument (edited by Shanghai Chemical Reagent Purchasing and Supply Station), but after careful reading, I realized that it can only measure fine sand and gravel particles with density greater than water, and the measurement accuracy is low. This is because the liquid level is too large, so that the liquid level does not rise significantly.
In order to invent a new instrument for measuring density with high precision, it is necessary to solve the problems that the liquid level of Lee's pycnometer is too large, the measurement accuracy is too low, and the inlet diameter is too small to measure the whole large-volume measured solid. The author's solution is as follows:
(1) Add a branch pipe. The inlet can be separated from the drainage pipe, so that the whole large measured solid can be put in.
(2) The capillary calibration tube is used to replace the original calibration tube, which improves the test accuracy by 10 times.
(3) Changing the branch pipe into the top of the glass plug can completely exhaust the air accumulated at the bottle mouth, thus improving the reliability of measurement.
The instrument can be made into a series of products with different ranges and specifications, and is simple to manufacture and low in cost. It is suitable for mass production and can meet the requirements of all walks of life for accurate determination of solid density.
6. Author's readme
I started choosing topics last summer vacation. Teacher Zhou Qinglin left me several series and method books of previous small invention projects. Inspired by it, I chose several topics, such as TV receiving antenna, convenient starter … including density bottle. At that time, I thought of density measurement from measuring the fineness of gold, and then I thought of the need to accurately measure the volume. I also checked the information (the catalogue of Shanghai Glass Instrument Factory) and learned that the accuracy of volume measurement can not reach the accuracy needed to distinguish the density of gold with different fineness, so I really want to invent a high-precision volume measuring instrument. Because I am learning this part of physics knowledge, I am interested in it. At first, I wanted to use the principle of gas volume change. After a preliminary conception, I submitted this project to Teacher Zhou. Teacher Zhou thinks that there is no duplication with the previous competition and it is feasible. At present, the demand for gold detection is also great and the direction is good, but in terms of methods, he believes that: first, there are many parts in the gas device and the device is complicated; Secondly, the gas changes too much with temperature, and the environmental conditions for testing are too harsh and unrealistic, which inspires me to find ways to improve traditional instruments. After returning home, I painted for an afternoon, and my thinking gradually matured, and gradually found the fundamental reason why the accuracy of the traditional instrument "Lee's pycnometer" could not be improved: the drainage pipe and the water inlet were male, and the water inlet was too small for the measured object, so the "Lee's pycnometer" had to crush the object, and only tiny sand and gravel solids could be detected; For the discharged liquid, the drainage area is too large, which leads to the inconspicuous height difference, and of course the accuracy is not high. So I want to open the container with two openings, one is the inlet, which can be changed at will, and the other is the capillary branch, so that the height difference of the liquid discharged from the capillary is very large, and substances of any size and shape can be accurately determined. However, in any case, it is impossible to meet the requirement that the initial height and future height of the liquid level are all in the capillary, and the feed inlet can be opened and closed freely without overflowing.
After a few days of thinking, I thought of how to make the initial liquid level indicator in the capillary tube so that the feed inlet does not overflow. One day, it suddenly occurred to me to suck water into the capillary, so that the liquid level at the inlet would drop, and the block could be added to the container, so that the water would not overflow. All you need is an ear wash ball. When adding a block, block the capillary hole with your finger so that the water will not fall off. Release your finger after joining, and the liquid level will fall back, indicating the height difference. After clarifying all the principles and ideas, I told Miss Zhou my thoughts.
Teacher Zhou carefully studied my schematic diagram and put forward several problems-my feed inlet is at the top, the branch pipe is at the side, and the air at the top cannot be exhausted after the liquid level drops above the branch pipe (as shown in figure 1- 1). The volume of this part of gas is changing, even if it is constant, then an instrument with both gas volume and water volume cannot be measured. I discussed with Mr. Zhou for a long time and suggested whether the branch pipe could be moved to the top, with the feed inlet at the side (as shown in figure 1-2). But glass worker Fu said: "It is too weak, inconvenient and too demanding to weld a top surface twice." So we opened a hole from the grinding plug of the feed inlet and inserted the branch pipe to make the branch pipe mouth flush with the bottle stopper. A few days later, after watching the actual operation, Mr. Zhou raised another question: one bubble was not completely discharged and was held back by the flat bottom of the rubber plug. The influence of the size and number of bubbles on such a precise instrument is far beyond the error range. He proposed to dig an inverted funnel shape at the bottom of the rubber plug with a blade. Bubbles do not hang on the inclined plane, but rise to the top and are discharged. After the instrument is reprocessed again, the objects will be sent to the area to participate in the selection.
The teacher in the district hit the nail on the head and pointed out that the rubber stopper is elastic, sometimes it is inserted deeply, and sometimes it is inserted shallowly, so the volume of water in the container bottle is different. Such a volume difference is a mistake, not an error measured by this instrument. Teacher Zhou was present at the time, and immediately proposed to replace the rubber plug with a glass grinding plug, which solved the problem. My density bottle was almost eliminated in the region, which made me clearly realize for the first time that invention is a real scientific work, not a theoretical model such as "ideal gas" and "particle" in books. Is to solve a sloppy little problem in practice, and every little problem can make you. From then on, I took discovering small problems and unpleasant things in real life as my pleasure, and took solving and improving them as an effective way to cultivate my ability.
When I entered the city for the competition, the density bottle was improved again. The capillary volume is too small, and the volume of water sucked up is not enough to make the liquid level drop, and the water will not overflow when put into the block. Our aim is to measure the density of objects of any shape and size. Teacher Zhou suggested opening another pipe on the side to increase the measurable range (twice the measurable solid volume) and installing a water storage ball above the side branch pipe to make the liquid level in the container drop more. After several processes, the water storage balls are too small. Through many experiments, it is finally found that the volume of the water storage ball is almost enough to be used as the volume of the container (it is not required to be very large, only 2 ~ 3 ml larger than the maximum volume of the object), and so many processing procedures are operated by the glass worker in my father's unit. At first, he didn't understand the principle. Sometimes the ball is too small, sometimes the side nozzle is too high, which makes the ball "not full", sometimes the capillary scale is too small or too much is wasted (too many scales under the unmeasurable line), which is often unsatisfactory in actual operation and even impossible to use. Later, I spent the afternoon drawing and explaining to him. After all his problems are solved, no matter what questions we ask, he can do it just right. I really realized the combination of theory and practice, which I thought was empty talk before, but it is actually a truth. To tell the truth, my biggest gain now lies not in winning the prize, but in learning so many things that are not available in class. I am excited to think that I will encounter so many interesting problems and learn so much practical experience and knowledge after entering the society. I like this activity. Let's enjoy solving problems together!
In view of the evaluation of the judges and teachers in the city-inconvenient operation, I improved the instrument again. Open the bottom of the container, connect a horizontal pipe, and then turn it into a capillary branch (as shown in figure 1- 3). In this way, a tee (switch) is welded on the horizontal pipe, so that you will never block the branch pipe with your fingers at the same time, just turn off the switch and the operation will be much more convenient. Water drops often hang on the pipe wall, which affects the accuracy. My father is a chemistry teacher, and he cleans the whole instrument with chrome pickling solution to make it clean and transparent. In the form submitted to the provincial competition, I proudly wrote that the instrument can be made into a series of specifications and ranges to improve the accuracy and test range.
In the process of operation, I also gradually explored a set of operation methods. Such as: the method of replenishing water; After continuous measurement for many times, water is lost, and then water is replenished (to prevent air from being mixed in the process of directly adding water, so that bubbles cannot be discharged from the pipe); Safe operation method of reloading pulley; Some practical experience such as the stable time required for reading.
On the eve of leaving for the national competition, several spare density bottles were broken, especially the joint between the horizontal branch pipe and the tee joint. We strengthened all the welds, and replaced the piston under the side branch pipe and the piston under the container scale, so that the length of the cross beam was reduced as much as possible, and the tee joint would not affect the measurable line height of the side branch pipe (as shown in figure 1-4). I also installed a series of shock-proof objects such as wooden frames and shock-proof mats to alleviate it. I also made a surprise test on the fineness of dozens of gold ornaments to welcome the national exhibition. It's really not easy to invent and make a real and practical thing. Although it still has many unsatisfactory places, its cost is very low (and the atomic spectrometer for measuring the color of gold ornaments costs about 50 thousand dollars) It can't measure the fineness of gold ornaments with diamonds, but atomic spectrometer can. I hope my density bottle can be more used in mineral processing, metallurgy and other scientific and technological fields, and play its greatest role. I hope that professional instrument manufacturers will be interested in my density bottle and improve it to make it more exquisite than the physical model. I hope this "capillary amplification" measurement method can improve the accuracy and instruments in more fields and give full play to the benefits of my best efforts as a middle school student. I hope that our school, our country, the world's invention and creation activities, and young students' scientific practice activities will last forever, be interesting and beneficial.
In addition, in terms of will, I am not strong enough, sometimes I am very tired, sometimes I think invention is a "crooked door", and sometimes I am lazy and not active. Teacher Zhou always urges me, educates me and encourages me to do things to the end. My parents gave me the greatest spiritual support and encouragement. My father wholeheartedly assisted me in making and improving the processing for more than a dozen times. My mother worked hard and carefully to arrange my exhibition materials clearly. The documents submitted at all levels have been carefully studied and revised by Mr. Zhou. I should thank organizations at all levels and my alma mater for giving me such opportunities, such conditions, such an environment and such teachers. I owe my achievements to everyone. Never dare to make contributions on your own. I still need to redouble my efforts to become a scientific and technological expert in the 2 1 century.
(This invention won the National Youth Invention Gold Award, the "Full Peak Award" of the IET Foundation of the United States and the first place of the Ilida Youth Invention Award. Mr. Yang Zhenning personally presented the award. Author: Cai Ying, then a sophomore; Instructor: Zhou Qinglin)
7. Analysis of works
(1) Question: The author's parents are both chemistry teachers. Shortly after I set up a "question field" to induce her to choose a research topic, she happened to read a glass instrument compiled by Shanghai Chemical Reagent Purchasing and Supply Station at home and became interested in the "Lee's solid pycnometer" introduced on page 106. This triggered her long-standing desire for an invention and design. It turns out that many people often take gold jewelry to her neighbor's house to measure the gold content, each piece 10 yuan. The results were not immediately available. She thought: Can you invent a cheap and short-term instrument to measure the gold content of gold jewelry? The quality of gold jewelry is known (even if unknown, it is easy to measure). The key is to find a quick method to measure the volume of gold ornaments. Fortunately, she found a new idea of invention from "Lee's pycnometer"-a new drainage method.
(2) Invention design: It is not difficult to see from the introduction that her invention design has solved two problems existing in the "Lee's solid pycnometer":
① Changing the large-diameter calibration tube of Lee's solid pycnometer into a small-diameter calibration tube (capillary tube) can solve the problem of improving the determination accuracy. (as shown in Figure L-5)
② The single branch of Lee's solid pycnometer was changed into double branches to solve the problem of measuring large-volume gold jewelry.
8. Comprehensive comments
(1) In the process of asking questions, the author adopted the methods of finding fault, finding demand and paying attention everywhere, and raised the question of whether a cheap instrument for measuring the gold content of gold ornaments can be invented in a short time.
(2) In the process of invention and design, the author adopted "transplant conversion method" (the application of "capillary amplification principle") and "addition and subtraction conversion method" (adding a branch pipe to overcome the shortcomings of the original instrument).
(3) According to the author's self-report, her design lasted more than a year and failed more than a dozen times, but it was only through persistent research that she succeeded. Therefore, in the whole process of invention design, she also adopted the "perseverance method".
9. Suggestions for improvement
Because the biggest drawback of this work is that it is fragile and inconvenient to transport and carry, so it needs to be handled with extra care.
(l) Is it possible to find a new material that is not fragile, has a small expansion coefficient and has good transparency to make works?
(2) If we can't find a new material with non-friability, small expansion coefficient and good transparency to do this work, it is suggested to adopt a movable connection between the two pipes to solve the problem of inconvenient transportation and carrying.
10. Invention relay
(1) Using the "capillary amplification principle" used in the invention, the change of tiny volume can be converted into the change of large length for invention design. For example, other high-precision measuring instruments or high-sensitivity alarms can be designed by using the principle of capillary amplification.
(2) Using other amplification principles, such as analog circuit amplification principle, digital circuit amplification principle, optical path amplification principle (see Cavendish experimental device), lever amplification principle, etc. Invent and design, and turn a small amount into a large amount.
Second, determine the topic (project) and put forward the hypothesis.
As long as the above-mentioned "problem areas" are colorful and inspiring, students can generally choose research topics quickly. For example, in the first case mentioned above, students can use group thinking or equal discussion to predict various possible causes (water pollution, inferior feed, abnormal climate, poor fry quality, etc.). ) lead to the imminent death (or extinction) of fish. Select the focus of attention, extract the main problems and determine them as research topics, clarify the direction of special research, and form research hypotheses or prediction analysis (such as river water may be polluted).
Three, formulate research plans, demonstration and implementation.
Make a research plan, start a project to demonstrate the feasibility of the research plan, and enter the research process according to the details of the research plan.
Fourth, collect and organize information.
Use various channels to collect data and information needed to solve problems. As in the above example, students can visit the residents by the river; Conduct field investigation, water sample analysis and dead fish anatomy analysis on the surrounding environment, and design and conduct relevant necessary comparative simulation experiments; Go to the library and consult information online; Wait a minute. Analyze and process the obtained information and data, and evaluate its effectiveness.
Five, comprehensive induction, draw a conclusion
Explain the data and information, form a general conclusion (for example, the investigation result is that the fish in the river are on the verge of death or extinction due to toxic sewage discharged from nearby chemical plants), verify the research hypothesis or forecast analysis, and express the conclusion in various forms, such as writing a news, making a model, making an invention, completing a report, writing a scientific research paper or creating a story.
Presentation and communication of intransitive verbs, and evaluation.
Through comprehensive induction, the above conclusions and related results (including all relevant raw materials in the process of obtaining the results) are presented to the project management department and all those who care about their research-based learning, so as to promote mutual communication and accept the evaluation and guidance of relevant experts and people, thus gaining the motivation and experience of research-based learning.
Seven, practice test, reflect the value.
If social action is taken, students are provided with opportunities to participate in decision-making, so that they can consider and determine practical action plans, report to government authorities, and contact relevant parties in the community to implement social action. For example, put forward reasonable suggestions to relevant government departments, urge government departments to punish chemical plants, assist chemical plants to put forward rectification or conversion opinions, and organize community environmental protection publicity activities.