Effect of detergent on life of goldfish
1. The topic is put forward:
Detergents are closely related to us in modern life. We use detergent to clean food (fruits, vegetables, etc.). ) and tableware are available almost every day. When we use it, most of the detergent will flow to rivers, lakes and seas with the sewer. Some time ago, we watched the news report of a provincial TV station, saying that detergent contains strong carcinogens, and the harm to human body can be avoided by repeated washing, but will it harm the fish in the river when it is discharged into the river together with our domestic sewage? Will it hurt the animals by the river? This series of questions aroused our interest and decided to prove our problems through experimental observation, so we carried out the research on this subject under our careful planning and arrangement.
2. Experimental purpose: To explain the harm of detergent to aquatic organisms (such as fish) through experiments and consulting data, and to preliminarily explore its harm mechanism, hoping to improve its ingredient formula.
3. Experimental methods: ① Determination of median lethal concentration; ② Respiratory frequency: gill cover activity count; ③ Determination of oxygen consumption: iodine determination; ④ Organ detection: anatomical method.
4. Materials and utensils: ① goldfish (goldfish is a common experimental fish, and the detergent is directly discharged into the water, which is obviously harmful to aquatic organisms) ② detergent (a commonly used detergent for cleaning fruits and tableware in the market, purchased in supermarkets) ③ experimental instruments; Glass containers with length, width and height of 20cm, 20cm and 40cm respectively, glass containers with length, width and height of 10cm, 10cm and 20cm respectively, 1000ml measuring cylinder, 10ml measuring cylinder, pipette.
5. Method steps: ① Make tap water for removing residual chlorine, first put tap water into a big iron drum, and then seal the drum mouth with a layer of gauze and rubber band. Then put it in a ventilated and light-transmitting place for natural aeration for more than three days to remove residual chlorine in tap water. ② Domestication of experimental fish: The water to be domesticated should be diluted water without any pollution (tap water for removing residual chlorine), and the domestication container is non-toxic. The domestication time is 30 days, and the number of goldfish to be domesticated is more than 150. During domestication, a small amount of bait that does not affect the water quality is put in every day. When the mortality rate is controlled below 10%, the experiment can be started. ③ Selection of experimental fish: The experimental fish must be healthy, and the judging criteria are normal body shape, complete scales, bright body color, lively action, sensitive response, good appetite, basically the same size, and no abnormal appearance and fish diseases. ④ Determination of median lethal concentration:
A. Preparation of experimental solution: The experimental solution should be prepared twice in this experiment. Nine different detergent concentration gradients, numbered 1-9, were prepared for the first time to find out the approximate lethal range. The concentrations of experimental liquid in L-9 cylinder are 10%, 1%, 0.1%and 0.0 1% respectively. 0.00 1%、0.000 1%、0.0000 1%、0.00000 1%、0%。 For the second time, after the approximate lethal concentration was obtained in the above experiment, ten arithmetic concentrations were prepared between all the lethal minimum concentrations and all the immortal maximum concentrations. Number A-J, plus 0% blank control, number k, get the semi-lethal concentration.
B. Put the experimental fish: After preparing the experimental solution, carefully transfer the goldfish from the domesticated container to the containers of each experimental group, and put 5 goldfish in each tank. After 30 minutes, the goldfish will start to observe and record on time after fully adapting to the new environment.
C experimental time: the experimental time is 48 hours, including continuous observation for the first 12 hours and observation at any time for the last 36 hours, and the death time of each group of experimental fish is recorded.
D. Judgment of goldfish's death: If the goldfish stops breathing, it can be judged as death if the tail handle of the fish (the part of the fish near the tail fin) is not stimulated within 5 minutes.
E. Using the second experimental data, use the following formula to calculate LC50. Median lethal concentration = (minimum lethal concentration+maximum survival concentration) /2 ⑤ Determination of physiological indexes of experimental fish (compared with blank group and median lethal concentration group).
A. Preparation of experimental solution: Re-prepare the experimental solution according to the semi-lethal concentration calculated in the previous experiment.
B. Release the experimental fish: put the experimental fish into experimental containers ① and ② with clean water (control group) and semi-lethal concentration (experimental group) respectively, and put five goldfish in each tank for 48 hours.
C. observation record: once every 4 hours. The contents of the observation records are: (a) respiratory frequency; (b) body surface and movement; (c) Response to stimulation (hitting the fish tank with a glass rod). ⑥ Dissect the fish after the above experiment: The observation contents include the changes of visceral color, body surface, eyeball and gill filament. ⑦ Determination of oxygen consumption of experimental fish: a. Put the control group and the semi-lethal concentration group into wide-mouth bottles, add rubber stoppers (there is no air in the bottles) after 30 minutes, and put them together with blank bottles (clean water bottles and semi-lethal concentration detergent bottles) without fish, and keep the temperature at 30℃ for 65438 0 hours. B) Determine the oxygen content of the water in the above bottles by iodine measurement, and then calculate the oxygen consumption of two groups of experimental fish by using the oxygen content of two blank bottles. The formula is as follows: oxygen consumption of experimental fish = (oxygen content of blank bottle water-oxygen content of experimental bottle water)/fish weight × storage time.
6. Record of results:
The final result of this experiment is that goldfish in different concentrations of detergent solution have different mortality rates, but goldfish in clean water still survive. The goldfish in different tanks, the highest concentration group died first, and then the fish in other groups died one after another. It can be seen that the concentration of detergent is positively correlated with the mortality rate of goldfish. It shows that its harm is related to concentration, and there is a concentration threshold.
A. respiratory frequency through observation, we found that the respiratory frequency of the two groups of fish was obviously different.
B. showing physiological and behavioral changes. In this experiment, through careful observation, we found that the goldfish in tank 1 had no physiological and behavioral changes, while the fish in tank 2 had obvious changes. It can be roughly summarized as follows: when the experimental fish was first put in, the breathing frequency of the two groups of fish was normal, with an average of 45 times per minute and rapid response. When stimulated, goldfish will immediately spread out or scurry around; Swimming speed and body color are normal. In the next 20 hours, the goldfish in the experimental group appeared floating head and slightly swollen belly. At this time, the goldfish's breathing times greatly increased, becoming 80 times per minute. After another eight hours, the goldfish had a turn for the better. The number of breaths changed from changeable to less, reaching at least 30 breaths per minute, and the degree of reaction was obviously reduced. When goldfish does not respond to general stimuli, it must touch its body surface with a glass rod to have a weak response. 12 hours later, we found that the skin of goldfish fell off, the body color gradually became lighter, and the previous bright color was lost, and the reaction became more serious. The color of the whole body is obviously lighter.
C. Anatomical characteristics Through the anatomy of two groups of experimental fish, we found that the internal organs of goldfish have little change in color and shape, and the contrast effect between the two groups is not obvious. However, when we observe the gill filaments of two groups of experimental fish, we find an important phenomenon: the gill filaments of normal goldfish are distributed in a radial network; And the color is bright red; However, the gill filaments of goldfish in the experimental group shrank; And the color is dark red. In addition, the epidermis and cornea of fish have obvious shedding phenomenon. Moreover, the fading phenomenon of the fish body is also obvious.
D. Oxygen consumption By comparing the data of oxygen consumption in the above table, we can know that the oxygen consumption of goldfish in the experimental solution is lower than that in the control group, indicating that detergent will lead to the decline of metabolic function of goldfish, thus causing the decline of oxygen consumption.
7. Analysis and discussion: By referring to the relevant conclusions and data of the above experiments, the experimental phenomena and results were analyzed, and the harm mechanism of detergents was preliminarily discussed. The main component of detergent is a synthetic surfactant, such as sodium alkylbenzene sulfonate in detergent. Its decontamination mechanism is that the hydrophobic end of the molecule has affinity for dirt (mostly lipids) and the hydrophilic end dissolves in water, thus dispersing the dirt in water and being washed. However, this substance will also act on the cell membrane of lipids, causing the membrane to disintegrate and the cells to die. During the experiment, the surface cells of the gill of snapper were also destroyed, which significantly reduced the gas exchange in the gill. Due to insufficient oxygen supply, gill filaments turn dark red due to lack of oxygen, and the natural oxygen consumption decreases obviously. Under the feedback adjustment of the body, by increasing the breathing frequency to try to increase the oxygen acquisition, goldfish intestinal wall will also appear floating head, bloating and other phenomena caused by swallowing and breathing. When this series of adjustment measures are still ineffective, hypoxia will eventually lead to the decline of functional metabolism, and then it will be manifested as abnormal phenomena such as decreased respiratory rate and slow response. Therefore, the respiratory frequency of fish will show a bell-shaped curve that first increases and then decreases.
It can be seen that the damage mechanism of detergent to fish is mainly manifested in the blocking effect on breathing, and eventually it will die of suffocation. However, during the experiment, we found that the epidermis and cornea fell off and the body surface and eyeball faded, which may be due to the role of surfactants and chlorides (used for oxidative sterilization) in detergent. Of course, in natural waters, because there is not such a high concentration and such a long action time, the performance is not so obvious, but its harm is objective. In addition, the detergent also contains a lot of phosphate (such as sodium tripolyphosphate), which can make the water eutrophication, which will certainly destroy the original balance of the aquatic ecosystem. Detergents are mainly composed of synthetic substances, which are difficult to be degraded and utilized by microorganisms. Imagine that a lot of detergent residues are discharged into the water body every day without being degraded. Once the lethal concentration of aquatic organisms exceeds half, the consequences will inevitably be the death of a large number of aquatic organisms and the collapse of the entire ecosystem. In addition, the foam produced by detergent will cover the water surface and reduce its reoxygenation speed and degree, which is particularly prominent in still water. The Thames in Britain is short of oxygen, and the estuary can smell the smell of hydrogen sulfide, which is mainly due to the pollution of detergent.
8. It is suggested that manufacturers of detergent can improve many related ingredients and remove harmful ingredients; In addition, the use of pollution-free cleaning products is advocated. Soap, for example, is a kind of pollution-free, harmless and environmentally friendly article, because its raw materials exist in the fat of plants or animals and are easy to biodegrade; You can also consider using enzymes as detergents to degrade protein and lipids in dirt (using a bio-generator to produce enzymes may reduce the cost).
Author: Qin Ri Xu Zihan Han
Fan wener
Changes of magnetic force of magnets in strong magnetic field and high temperature environment
purpose
In order to find out that the magnetism of magnets is influenced by high temperature and strong magnetic field environment, and to find out the Curie temperature of V-shaped magnets commonly used in our research, we have carried out experiments.
think
In order to find out the change of the weakening or disappearance of the magnetic force of the magnet, we are going to adopt the method of simulating these two environments. Simulation of strong magnetic field environment with DC electromagnet; The high temperature environment is simulated by a high temperature electric furnace.
tool materials
Permanent magnet: two pieces, which are U-shaped and bar-shaped.
Gauss meter: model 4 10, made by LakeShore, with minimum resolution of 0. 1GS and measuring range of 2000GS.
Power supply: DC steady current power supply, with maximum output current of 400A and maximum output voltage of 50 V. ..
Bipolar DC electromagnet.
The box-type high-temperature electric furnace RJX25- 13 produced by Tianjin Electric Furnace Factory has a maximum heating temperature of 1350℃.
manufacturing process
V-shaped magnet and bar magnet were measured by Gauss meter, and placed in strong magnetic field and high temperature environment respectively. The current input to the electromagnet and the temperature of the electric furnace are constantly changing, and the data are recorded and finally analyzed.
scientificity
This experiment got accurate data, and then got some simple physical conclusions.
progress
This experiment is entirely designed by students themselves, not limited to the data in the materials, and the answer to the question is found through the experimental method designed by them.
innovate
According to the idea of designing the experiment, the specific operation method is put forward and the final conclusion is drawn.
Introduction of works
In daily life, the direction and size of the original strong magnet will change due to the strong magnetic field environment. For example, the magnetic force of a small magnet will weaken under the interference of two large magnets; When the magnet is placed next to the furnace, the magnetic force will weaken at high temperature; The nails will be magnetic after a period of time. We have consulted a lot of materials and know that each magnet has a different Curie temperature, that is, magnets will lose their magnetism at this temperature. So what is the Curie temperature of magnets that we often see in our study? With many questions about the weakening and disappearance of the magnetic force of magnets in our life and study, we carried out specific experiments and got accurate and quantitative physical conclusions.
After careful analysis and data search, we found that the conditions to weaken or disappear the magnetic force of magnets are: high temperature environment, strong magnetic field environment and strong vibration. We mainly introduce the experiment that the magnetic force of magnet weakens or disappears under high temperature and strong magnetic field. The purpose of the experiment is to find out the change of magnetic force of magnets in high temperature environment and find out some laws as much as possible. It is expected that some general trends and simple laws can be found in the curve image composed of the final data.
We use a gauss meter to measure the magnetic field of a magnet. In order to make the data more accurate, we adopt the method of multi-point measurement of magnetic poles, that is, taking the midpoint of a magnetic pole as the main measurement point and four points at the four corners of the magnet as the auxiliary measurement points. Because the distribution of magnetic induction lines at the four corners of the magnet in the permanent magnet is overlapping and inaccurate, and the center can accurately reflect the magnetic field value of the magnetic pole, we take the magnetic field value at the center of the magnetic pole as the most important data in the data, and name the specific points as the four corners of the N pole. The four corners of the s pole are e, f, g and h respectively; The midpoint of n pole is p, and the midpoint of s pole is q.
1. Experiments in strong magnetic field environment
In the laboratory, we first measure the magnetic field values of N and S poles of bar iron with Gauss meter, and then put it into DC electromagnetic field. At this time, the DC current rectified and filtered by the steady-current power supply is fed into the DC electromagnetic field with a certain amperage, and the magnetic field value in the strong magnetic field is measured with a Gauss meter. Then turn off the steady current power supply, take out the bar magnet, and measure the magnetic field values of N and S poles with a Gauss meter again. After comparison, repeat the above steps, only gradually increase.
2. Experiments in high temperature environment
In order to find out the influence of temperature on the magnetic force of the magnet, we heat the magnet with a high-temperature electric furnace and measure the magnetic field value of the magnet with a Gauss meter. When we measure magnets, the limit of temperature rise is 20℃. Because the conditions are not allowed, and we see that the magnetic field value of the magnet does not change much at high temperature and cooling, we only measure the magnetic field value when the magnet is taken out of the electric furnace and cooled with water.
3. Re-magnetizing experiment of U-shaped magnet.
At the end of the experiment, we are going to put the magnet that has completely lost its magnetism into the DC electromagnet for magnetization, that is, place it in a certain direction (that is, place it sideways so that the magnetic induction line of the DC electromagnet conforms to the original distribution of the magnetic induction line of the U-shaped magnet as much as possible, so as to truly achieve the purpose of magnetization), then apply 400A current to the electromagnetic rail, cut off the electromagnet five seconds later, take out the magnet, and measure S as -as after measuring with a Gauss meter.
The data finally measured in this experiment basically meets our expectations, and the curve presented by the data in the strong magnetic field environment is irregular. By comparing the curves, we can see that when the current applied to the electromagnet is less than 20A, the magnetic field values of the positive and negative magnetic fields of the magnet change little, but the magnetic pole and magnetic field values of the magnet change greatly. When the input current is greater than 20A, the five measuring points of the N pole are greatly reduced, averaging about one sixth to one seventh, while the S pole also changes greatly. When the input current changes from 1 8A to 2 1A, S is extremely negative. In addition, not only the numerical value changes greatly, but also the polarity is deflected. Three of the five points we measured were offset. The reason why the magnetic field value of two poles changes greatly is that when the current of DC electromagnetic field is 2 1A, the magnetic field value in electromagnet obviously exceeds the magnetic field value of two poles of magnet, so it will have a great influence on magnet. In the subsequent measurement, the magnetic field value of the magnetic pole changes little. Until the input current increased to 40A, several auxiliary measuring points of N pole were deflected, and the value of the main measuring point became very small, while the magnetic field value of S pole was completely positive, indicating that the two poles of the magnet had completely changed at this time. Then we increase the input current to 200A A. At this time, the magnetic field in the electromagnet is 10 times higher than that when the input current is 40 A. At this time, the magnetic pole of the magnet is already opposite to the symbol drawn outside, and the S end of this magnet can attract the S end of an ordinary magnet. In the experimental data in high temperature environment, we can clearly see that the magnetic field values of point P and point Q of N and S decrease with the increase of temperature, and the magnetic field values decrease fastest between 220℃ and 300℃. When the temperature in the furnace reaches about 300℃, the magnet is heated to a red-hot state, and when the temperature reaches 340℃, the magnetic field at both poles of the magnet drops to a very small level, and the temperature reaches 360℃.
The magnetic force of the magnet will change in the high temperature and strong magnetic field environment: the magnetic force of the magnet will weaken or even disappear in the high temperature environment; The magnetic field direction of the magnet will change in the strong magnetic field environment, and even the magnetic pole will deflect; Metals without magnetism will have a certain magnetic force in a strong magnetic field environment.
Everything is made up of its molecules, and molecules are made up of atoms, and atoms are made up of electrons inside and outside the nucleus. Electrons constantly revolve around the nucleus, and these two movements of electrons will produce magnetism. However, due to their different directions of motion, the orientation of molecular currents in ordinary metals is chaotic, and their magnetic fields cancel each other out and are not magnetic to the outside world. Under the action of external strong magnetic field, the primary electrons and moving electrons in some substances are arranged neatly. At this time, the magnetic effect produced by electron rotation is consistent with the direction of external magnetic field, and the substance is magnetic. The reason why the magnet can hold the nail is because when the magnetic magnet is close to the nail, the atoms in the nail are magnetized by the magnet. Similarly, if a normal magnet is placed in a strong magnetic field environment, the magnetic effect of electron rotation inside the magnet is different from that of the external magnetic field, so the orientation of some electron rotation inside the magnet will change due to the interference of the external strong magnetic field. At this time, the orientation of electron rotation inside the magnet will be different, and some molecular currents will cancel each other, which will make the direction of magnetic field inside the magnet change greatly and even lead to magnetic pole deflection. The reason why the magnetic force of a magnet disappears in a high temperature environment is that the molecules in the magnet will accelerate their thermal motion in a high temperature environment, thus changing the regularity of the movement direction of electrons, making the molecular currents cancel each other out, thus weakening the magnetic force of the magnet until it disappears. Re-magnetize the magnet, so that the electron arrangement of atoms is regular again, and the magnet that has lost its magnetism becomes magnetic again.
Through this experiment, we have a deeper understanding of the demagnetization of magnets, and we can better serve them by using the Curie temperature of magnets and the properties of magnetic pole deflection. For example, the temperature control device at the bottom of the rice cooker makes use of the Curie temperature of the magnet. The device uses a magnet with Curie temperature of 105℃, and the magnetism will recover after cooling. When the water in the pot is dry, the temperature of the food will drop from 105℃. When the temperature reaches about 105℃, the magnetism of the magnetic substance attracted by the magnet disappears, and the magnet loses its attraction. At this time, the spring between the magnet and the magnetic material will separate them, and at the same time turn off the power switch to stop heating. If it is not convenient to measure the temperature, you can put in a magnet with known magnetism. Finally, the maximum temperature can be estimated by analyzing the change of the magnetic field value of the magnet. These characteristics have played a great role in safety switch and fire fighting. Of course, these are some ideas, and we need to make further efforts to realize them.
Authors: Yu Shanting, Yang Na, Liu Bin,
That's it ~O(∩_∩)O haha ~