Ma Chunsheng Wang Youning Tianjiabing Senior High School in Nanjing, Jiangsu Province, Nanjing 210037, Jiangsu 1. Activity Background 2. Activity Objective 3. Activity Plan V. Summary of activities Party Scene Decoration,Rainbow Latex Balloons,Rainbow Party Decoration, Scene Setting Balloons Xiongxian Tonghai Latex Products Co., Ltd , https://www.tonghaiballoon.com
With the development of social economy, the catering industry is more and more prosperous, and the demand for edible oil in the catering industry is also increasing. After the "Qing" period, masquerading as cooking oil entered the catering market, harming the health of consumers. According to reports, 3 million tons of drain oil is returned to the table every year in China.
Ditch oil is waste oil produced by the catering process and waste food. During the food processing process, due to high temperature frying, cooking, and adding various ingredients, the color and smell of the ditch oil are very different from pure edible oil. If criminals want to dispose of sewer oil as commercial edible oil into restaurants and restaurants, they need to treat the sewer oil to deodorize and "clear" it.
The theme activity of "Uncovering the Secrets of Drainage Oil's" Clearness "is to mobilize all classmates to search through the Internet to understand the harm caused by the inflow of the drainage oil to the catering industry, to understand the harmless treatment methods of the drainage oil, and establish The chemical science and technology activity group designs experiments and analyzes the experimental results, so as to uncover the secrets of the “clearing†of gutter oil. In the course of the activities, students ’awareness of food hygiene prevention is raised, and their chemical and scientific literacy are improved.
Cooperate with the school's science and technology activity week to educate students to strengthen food safety, improve students' scientific literacy and chemical literacy, and improve the ability to identify fake and inferior food.
Search through the Internet to find information, understand the hazards of sewage oil and the method of harmless treatment of sewage oil; design the experimental program of "clearing" of sewage oil, conduct the experiment of "clearing" of sewage oil, and analyze the experimental results, so as to Uncover the secret of "clearing" the drain oil.
Activity form: the whole class is combined with the chemical technology activity group
Activity method: Internet search survey method, chemical experiment inquiry method, the specific steps are shown in Table 1.
4. Activity process
1. Activity mobilization
Teachers use the chemistry class to mobilize the whole class, request students to actively participate in the school science and technology activities, and actively participate in the theme of "Uncovering the Secrets of Draining Oil". Recognize the harm to human body caused by the inflow of gutter oil to the catering industry, the method of harmless treatment of gutter oil to turn waste into treasure, and design an experimental plan on how to clear the gutter oil.
2. Web search survey and writing of small papers
Organize students to use their free time to go to the school's electronic reading room to conduct online search and investigation of news, hazards, and harmless treatment methods related to gutter oil, and organize and process the collected data, write small papers, and submit them in the form of electronic documents cross.
Achievements of online search investigation activities: received 37 small papers submitted by students. Topics include sources of drain oil, hazards of drain oil, and rational use of drain oil.
Using the chemistry class time, the student representatives made a survey report in the class, and the whole class had a better understanding of the hazards of sewage oil and the method of harmless treatment. At the same time, a group of 8 students formed a chemical science and technology activity group to "uncover the secrets of" draining "the oil.
3. The chemical science and technology activity group designs the experimental scheme of "ditch oil clearing"
The teacher guides the members of the activity group, and asks the classmates to design the "experimental plan to make the drain oil 'clear'". The students were divided into 3 groups, discussed and researched and submitted 3 experimental schemes.
What substance is used to decolorize drain oil is the most controversial issue among the students in the group.
Some groups thought of decolorization with SO2, some thought of decolorization with chlorine water, and some thought of decolorization with ozone. Under the guidance of teachers, the students discussed the convenience, cost, and whether the oil will deteriorate after decolorization. Finally, they reached a consensus to decolorize with zeolite. The experimental steps of drain oil clearing were discussed and the experimental procedures were clarified.
Drainage of gutter oil → heating and adding zeolite for decolorization → filtering the decolorized oil → clearing gutter oil
4. Carry out the experiment of "clearing" the drain oil
Experimental materials: "Gutter Oil" collected by students, homemade filters, magnetic heating stirrers, beakers, test tubes, glass rods, funnels, gauze, etc.
Experimental steps and records:
(1) The state of the drain oil: reddish brown, with the smell of spices, there are many food residues in the oil.
(2) Filter the drain oil. The students used self-made filters to filter, as shown in Figure 1. Due to the high viscosity of the gutter oil, the screen is used for filtering to remove most of the solid impurities in the gutter oil. The filtered oil is dark red and has a spice flavor.
(3) Add zeolite to the filtered gutter oil and heat
The heating instrument uses an electromagnetic stirring heater, as shown in Figure 2.
See Table 2 for heating experiment records.
(4) Filter the heated oil again, assemble a filter with a funnel and filter paper, and filter the oil while hot. The oil obtained was pale brownish yellow and the oil became clear. The oil is cooled to normal temperature, and the oil solidifies into a yellow solid.
During the student experiment, Professor Hao Jinghua from Nanjing Normal University came to our school to guide the scientific and technological activities. Professor Hao was very interested in the activity of “Uncovering the Secrets of Drainage Oil's“ Clearness â€. communicate with.
5. Analysis and thinking of experimental phenomena
(1) Why not use sulfur dioxide, chlorine water, ozone as decolorizing agent?
The colored substances dissolved in the drainage oil are mainly capsaicin and pigments in soy sauce. Sulfur dioxide can decolor some colored substances. It is not certain whether the capsaicin in oil and the pigment in soy sauce can be decolorized. , After heating, it will still return to the original color, and can not produce the effect of decolorization.
Chlorine water and ozone are both strong oxidants, which are inherently toxic and will oxidize the double bonds and some tube energy groups contained in the oil to produce new toxic substances.
(2) Why does the drain oil boil when it is heated to about 100 ℃, and the noise is heard?
Ditch oil contains water. When the temperature is around 100 ℃, the water boils and there is a noise. The boiling point of the fat is above 200 ℃. When the water is evaporated, the fat will no longer boil and the noise will disappear.
(3) Why does the redness of the oil disappear when the drainage oil is heated to 160 ～ 180 ℃?
Guess one: At this temperature, the adsorption force of zeolite is the strongest (similar to the active temperature of the catalyst), and the capsaicin in the oil is adsorbed and discolored.
Conjecture 2: At this temperature, capsaicin vaporizes or decomposes, causing the redness of the oil to disappear.
Experimental verification: To prove the above-mentioned conjecture, we took some trench oil without zeolite and heated it directly. When heated to 160 ～ 180 ℃, the red color of the grease faded, but there was coking at the bottom of the beaker. The brown color of fat is darker than that of zeolite.
Conclusion: The capsaicin in the gutter oil decomposes or vaporizes at 160-180 ℃, but the zeolite can absorb the pigment and carbon particles of soy sauce contained in the oil and prevent the coking phenomenon at the bottom of the beaker.
(4) Why does the smell of spices fade when the drainage oil is heated to 160-180 ℃?
During the processing of the dishes, some spices are added, and these spices will be dissolved in the oil. Therefore, the ingredients of the spices are contained in the drain oil. When the drainage oil is heated to 160-180 ° C, the organic molecules that make up the fragrance will volatilize or decompose, so the fragrance of the drainage oil after heating will be lightened.
(5) After the hot oil is filtered, why does the color become lighter and clearer?
Hot oil contains zeolite powder that has adsorbed colored impurities. After filtration, the powder is separated from the oil and the oil becomes clear.
(6) Can the drain oil become clear?
Not edible. The above experiment only removed the pigment and solid particles in the oil. A large amount of harmful organic substances (such as dioxins, etc.) dissolved in the drain oil are not removed. After human consumption, it is very harmful to the body.
(7) How to distinguish between normal edible vegetable oil and "clear" drainage oil?
Normally edible vegetable oil (harmonic oil) has a yellowish color and low viscosity. It is liquid at room temperature and has no odor.
The "clear" gutter oil is darker in color, contains animal fat, has a higher melting point, may solidify at room temperature (depending on the content of vegetable oil in the oil), has an odor, and is turbid. Filter with filter paper).
(8) How to use drain oil reasonably?
Ditch oil is discarded into the environment without treatment, which seriously pollutes the environment, so it must be recycled. Ditch oil is a good fuel and can be made into biodiesel for use in automobiles.
(9) How did the criminals "clear" the drain oil?
From the above experiments and analysis, we believe that criminals can “clear†the drain oil by a very simple method.
The steps may be:
â‘ Collect sewer oil (animal oils, vegetable oils) separately.
② Heat the grease to about 80 ℃ to melt it.
â‘¢ Set aside the hot oil to precipitate food residues and oil moisture layer, scoop out the upper layer oil (and filter with gauze).
④ Heat the scooped grout oil to 160 ～ 180 ℃ and keep it for a period of time to let the pigments and spices in the oil volatilize or decompose. Cooling, you can get the "clear" gutter oil.
This event was a complete success. Taking the method of the whole class participating in the combination with the group experiment, a popular science practice activity for all students, students who are interested in chemistry learning also learned through the experiment to apply chemistry experiments to solve problems in life, which improves the analysis of problems and The ability to solve problems has improved chemical literacy and scientific literacy.
The students wrote in the summary of the experiment: "This theme activity has benefited a lot. We encountered many difficulties in the investigation and experiment, such as how to make the drainage oil become yellowish. I thought about using sulfur dioxide and activated carbon. , But the results were unsuccessful. We gained experience from one failure after another, and finally achieved success. And in the whole process, we not only learned some chemistry expertise, but also learned how to face setbacks. In short, this topic The event has given us a lot. "
Food safety is related to people's health. Through the theme activity of "Uncovering the Secrets of Draining Oil to 'Clear'", students were able to truly feel the harm caused by draining oil to human health, and knew the process of making fake cooking oil. This theme activity, starting from the students' existing experience and the actual social life to be experienced, all classmates apply modern technology and network in the activity to conduct a data search to help students realize the close relationship between chemistry and life and improve students Attention to social issues related to chemistry has cultivated students' sense of social responsibility, participation awareness and decision-making ability.