The experimental report is divided into several parts. You just have to write each part carefully. The key point is to write the experimental results and experimental analysis, because the other parts are similar to each other, and the teacher will not look at them particularly carefully, but the results and analysis are different. You must summarize and analyze them according to your own experimental phenomena. Writing an experimental report is divided into experimental items, experimental purposes, experimental principles, experimental processes, experimental results, experimental analysis and thinking questions. The following is posted from the Internet for your reference, but remember, the report is not uniform. We must respect the experimental results, operate and analyze them correctly, and write an experimental report with our own thinking elements. 1. experimental purpose 1. master the operation skills of dissolution, filtration, evaporation and other experiments. 2. understand the chemical principle of separation of mixtures by filtration. 3. realize the application of filtration principle in social practice such as life and production. 2. experimental instruments and medicines: crude salt, water equipment: tray balance, measuring cylinder, beaker, glass rod, medicine spoon, funnel, iron shelf.

Filter paper, scissors, matches and pieces of paper III. Experimental principle Crude salt contains insoluble impurities such as silt and soluble impurities such as: etc. Insoluble impurities can be dissolved and filtered.

Remove it, and then evaporate the water to get the pure refined salt. 4. Experimental operation 1. Dissolve 5 grams of crude salt (accurate to 0. 1 g) with a tray balance. Measure 10 ml of water with a measuring cylinder and pour it into a beaker. Add a spoonful of crude salt to the water with a medicine spoon and observe what happens. Stir with a glass rod and observe. ). Then add the crude salt and stir it with a glass rod until the crude salt is no longer dissolved. Observe whether the solution is turbid. Weigh the remaining crude salt on the balance and calculate how many grams of crude salt are dissolved in 10 ml water.

2. Filter according to the method described in basic operation 6 of chemical experiment. Carefully observe the residue on the filter paper and the color of the filtrate. When the filtrate is still turbid, it should be filtered again.

If the filtrate is still turbid after two times of filtration, the experimental device should be checked and the reasons should be analyzed. For example, the filter paper is damaged, and the liquid level in the funnel is higher than the edge of the filter paper during filtration, and the instrument is not

Clean, etc. After finding out the reason, re-operate. 3. Evaporate and pour the clarified filtrate into the evaporating dish. Put the evaporating dish on the iron ring of the iron frame and heat it with an alcohol lamp (Figure 20). At the same time, stir the filtrate continuously with a glass rod.

When a large amount of solids appear in the evaporating dish, stop heating. Use the waste heat of the evaporating dish to evaporate the filtrate.

4. Transfer the solid to the paper with a glass rod, weigh it and recycle it to the container designated by the teacher. Compare the state of salt before and after purification and calculate the yield of refined salt.

　　　　　　　　　　　　

V. Experimental summary

Analysis of Problems in Filtering Operation

Filtration is the most commonly used experimental operation to separate liquids from solids. The current junior high school chemistry textbooks only briefly introduce the main points of filtration, but in the actual operation process, many detailed problems are often encountered. The author talks about his own solutions to the problems often encountered in filtration operation, for reference only. (1) How to choose funnel and filter paper? The size of the funnel mainly depends on the amount of sediment or precipitated solids to be filtered, not on the volume of the liquid. If there is more sediment or solids, the funnel will be larger, and vice versa. The cone angle of the funnel should be 60. The pipe diameter is appropriate, too thick to keep the water column, and it will take too long to filter. The end of the pipe diameter should be slightly inclined. The selection of filter paper depends on the experiments done. Qualitative filter paper and quantitative filter paper. Quantitative filter paper is mainly used for quantitative analysis of substances. In middle school experiments, filtration operation is often used for qualitative experiments, so qualitative filter paper is mostly used. After the selected filter paper is put into the funnel, the edge of the paper should be about 5 mm lower than that of the funnel. (2) How to assemble the filter? First, fold the selected filter paper in half twice, and the second folding should not completely coincide with the folding seam of the first folding. When such filter paper is put into a funnel (the top angle is 60), there is a certain gap between its sharp corner and the funnel wall, but its upper part can be stuck on the funnel wall perfectly. The filter thus installed is faster than the filter with all surfaces stuck on the funnel. When folding, don't press the folding seam of the top angle of the filter paper too flat. So as not to weaken the strength of the tip. Then cut off the small corners of the two layers on the other side of the three layers of paper, so that the upper part of the filter paper can be closely attached to the funnel wall after wetting. Secondly, put the folded filter paper into a suitable funnel, wet the filter paper with water for washing bottles, and gently press the upper part of the filter paper 1/3 on the funnel wall with your fingers. When injecting water into the funnel, the funnel neck should be filled with water, or block the end of the funnel neck with your fingers. When filtering, the glass rod is opposite to the mouth of the beaker containing the filtrate; The end of the glass rod is close to the three layers of filter paper in the funnel, but it cannot touch the filter paper; Keep it vertical (I think that the glass rod is inclined to cause the filtrate to overflow); The tip of the neck of the funnel is close to the inner wall of the mouth of the beaker that receives the filtrate. The liquid transferred each time should not exceed two-thirds of the height of the filter paper, so as to prevent the filtrate from flowing out of the wall without passing through the filter paper. For the liquid and solid substances remaining in the beaker, it should be moistened with solvent or distilled water according to the principle of a small amount for many times, and all the washing liquid should be transferred to the funnel for filtration. (4) How to wash the sediment correctly? If it is necessary to wash the sediment, it should be washed immediately, otherwise the sediment will crack or agglomerate after being placed on the filter paper for too long, and it is not easy to be moistened. It can be moistened with the original solvent, distilled water or other appropriate detergents. Replace the beaker that originally received the filtrate with a clean empty beaker, so as to avoid re-filtering a large volume of liquid because the sediment penetrates the filter paper. The amount of washing liquid should be appropriate to immerse the collected sediment every time. When washing, Wash the sediment carefully from top to bottom around with a small amount of lotion, and flush it to the bottom of the funnel. Do not make the liquid flow too fast, otherwise it will make the sediment rush out of the filter. Do not stir the material in the funnel with a glass rod, so as not to cut the filter paper, and all previous efforts will be wasted. Generally, wash it for about 2 to 3 times, and you can basically wash it (5). How to check whether the sediment is washed? According to the types of impurities that may be detected on the sediment, appropriate reagents can be added to the last eluate to check the washing degree. For example, when filtering the mixture of Na2SO4 and BaCl2 after the complete reaction, to check whether the sediment is washed, AgNO3 solution should be selected. If AgCl is not generated by adding AgNO3 solution to the last eluate, it means that the sediment has been washed. (6) When filtering, there are too many filtrates. The funnel and filter paper can be washed with a small amount of original solvent for 2 to 3 times, and the original filtrate and washing liquid can be filtered again. (7) Is it necessary to use filtration operation to separate precipitation and liquid? No. When the amount of separated sediment is small, it can be placed in a centrifugal test tube, and the sediment can be separated by a centrifuge at room temperature. The supernatant of the sediment can be sucked by a straw. If necessary, it can be washed and then centrifuged. Only when the amount of sediment is large, it is suitable to separate by filtration. (8) Is there any other way for filtration? Yes. In order to make the filtration fast and convenient for washing, the Buchner funnel can be used for vacuum filtration, which makes the filtration and washing less time-consuming and convenient for washing. When the filtration needs to be carried out at a certain temperature, the insulation funnel should be used for filtration.