Since I crossed the gate of primary school, I have taken many classes, such as vivid Chinese class, interesting math class and mysterious nature class. One of the lessons can naturally make me remember.
It was a Tuesday morning a year ago, and school was almost over. Teacher Hou gave us an assignment, and everyone went home to prepare two eggshells. We all guessed the purpose of eggshells. Some guess that the teacher asked us to draw eggs, some guess that the teacher asked us to do experiments, and some say that the teacher wants us to learn wonderful math knowledge and see that we are curious. The teacher smiled and said, "The next class can be announced automatically."
After class, the teacher guessed our idea and said, "We are going to do experiments with this eggshell." Haha, I think I guessed the teacher's intention. "Students, you see this eggshell, which is easier to break, the arched side or the concave side?" Students all think that concave edges are easy to break. I did several experiments over and over again, but the sides of the arch could not be broken, which puzzled the students.
The teacher looked at us puzzled and told us, "This is the principle of thin shell structure, and the arch surface can offset the external force and make the structure stronger." The principle of thin shell is everywhere, so we should be good at discovering and digging. "
I found helmets, windshields, etc. Also based on the thin shell principle. Teacher Hong's class left me with a lot of thoughts.
The bell rang and the students hurried into the nature lab. We are staring at the door, because we are going to do a little experiment in this class today.
After a while, the teacher strode into the classroom, holding a lesson preparation book and a red eggshell egg. The students' eyes were fixed on the eggs. I thought: What experiment can an egg do?
The teacher went to the podium, held the egg high and said mysteriously, "Today we are going to do an experiment. Whoever can crush this egg will get this Swiss watch. " The students cried when they heard a "wow". The students raised their hands excitedly, and the teacher asked inexplicably, "Who is the strongest male student in our class!" Everyone's eyes fell on Xiao Deng. He swaggered to the front of the platform, took the' egg' from the teacher, spread his legs and assumed a posture. The timid little red hid under the table for fear that the egg white and yolk would fly to her. Xiao Deng clenched his teeth and squeezed hard. His face flushed, but the egg was intact, so he had no choice but to come down. The teacher said, "What a Hercules, that's all!" " "I shouted," I can crush it! " "The teacher turned his eyes to me. I walked up with confidence, took the egg from the teacher and silently read: egg, egg! Help me! I tried my best to squeeze it, but it wouldn't break. I sighed. The teacher said cheerfully, "Who is still unconvinced? Pinch again! " Next, the bold students didn't crush it. The teacher smiled and asked, "Do you know why eggs can't be crushed?" Students, look at me and I will look at you. Finally, the teacher said that the answer was solved: the problem lies in the shape of the egg, which is oval. When kneading, the force is evenly distributed to every part of the eggshell, so it will not break.
I really opened my eyes today. It turns out that a small egg also contains such a big scientific truth!
In science class, the teacher asked us to observe the cells in the onion epidermis under the microscope. I am very excited: finally there is an experiment "higher"!
The teacher asked every two students to form a group, so I naturally joined my deskmate Pang Yujie. We quickly prepared the materials: a knife, two onions, a Petri dish, a dropper, a beaker filled with iodine, a pair of tweezers and a microscope.
The experiment began. Pang Yujie first drew a "well" on the onion with a knife. We only took the "mouth" in the middle, but the onion skin was so thin that the tweezers broke as soon as they were clamped. After many efforts, we finally peeled off a small piece of onion skin.
The next step is to make slices. Let's first drop two drops of water on the glass slide with a dropper, then put the onion skin on it, and finally cover it with a cover glass, and you're done. However, those hateful little bubbles always stay in the slice and hide, so we have to uncover the cover glass and cover it again. After playing for 300 rounds, our little bubble was finally driven away by us. The teacher told us that the onion skin is transparent and should be dyed with iodine. Pang Yujie and I still cooperate in an orderly way: I gently lift the cover glass with tweezers, and he is responsible for dropping iodine into it with a dropper. But I found that the slice was sealed. Hardly had I pressed the cover glass when all the liquid in it came out, let alone dyed the onion. After we tried it more than five times, the onion finally "gave some face" and became a little brown.
You can start observing. I can't wait to adjust the microscope, put the slice on it, and craned my neck to look down from the eyepiece. But after looking at it for a long time, I can hardly open my right eye, and I still can't see any cells, only long eyelashes and blurred images. I had to let Pang Yujie change shifts, so I secretly looked at the teacher's microscope. The image inside is very clear: there are many rectangular grids in the onion skin slices, and there are several purple nuclei in the middle, which is simply another world! I am not reconciled, and I have returned to my "post". This time, I tried to adjust the distance between the objective lens and the stage. Suddenly, several purple spots caught my eye. Ah, I finally saw them! They are like "small eyes", smiling at me, as if to say, "Congratulations, the experiment was successful!" " "I suddenly feel that the whole world is so full of vitality. It turns out that there is another world in this tiny world, and I have seen them through my own efforts!
The experiment is over, but I think I will never forget those magical "little eyes". What a wonderful experiment this is!
In the second Chinese class this morning, the Chinese teacher came to the podium with a raw egg, a chopstick, a glass of water and a bag of salt. When the students saw it, they began to chirp. Some students said, "Is it difficult for the teacher to make drinks for us?" Some said, "What does the teacher want?" Suddenly, at the teacher's command, the classroom that was just chattering suddenly became silent. At this time, the teacher said mysteriously, "Let's do an experiment to make eggs surface." I thought: how can an egg float? What medicine is sold in the teacher's gourd?
The experiment began, and the teacher put the eggs in clear water. Eggs sink to the bottom of the water, just like a sleeping doll and a golden dough lying on the bottom of the water. The Chinese teacher put a little salt in the cup and stirred it with chopsticks, but after a while the egg sank, huh? What's going on here? Is there too little salt? Then, the teacher put a lot of salt in the cup. The teacher stirred hard with chopsticks, the water gradually turned milky white, and the eggs slowly floated up, just like a submarine slowly floated up. The students were surprised to see it and talked about it one after another. Some said: How can eggs float? Some are burying their heads in thinking at their desks. The teacher told us that the proportion of water is smaller than that of eggs, so the eggs will sink to the bottom. If you add salt to the water, you can increase the proportion of water, so that the eggs will float slowly.
I'm really surprised and happy. The world is really wonderful.
At noon today, the teacher informed us to bring the test box and go to the chemistry experiment class after school in the afternoon. I'm so happy. It has been three or four months since I spent more than 200 yuan on a test box. Just sleeping at home, my mother nagged that it was useless to spend so much money. I regret it, too. I might as well buy a book with this money A chemical experiment class, I finally look forward to it.
In the afternoon, I hurried to school with the experimental box and Liu Zongyuan. I finally looked forward to the time of school, but Mr. Shen asked me to go to school to rehearse my dedication. I quickly said, "teacher, I'm going to the chemistry experiment class?" At least Mr. Shen promised me to go to the experimental class, and I ran five with the test box. Sit in the middle of the front of Class One classroom and wait for the teacher to come.
Soon, the teacher came. The teacher's surname is Xu, and he seems to have rich knowledge of chemistry. He first introduced us to the use of chemical props (brushes, medicines, measuring cups), and then let us take out a chemistry manual to teach us to do chemical experiments. The teacher took out a bottle of calcium hydroxide, a bottle of water, a little calcium hydroxide in an empty bottle, four test tubes of water in a test tube, then covered the bottle cap and shook it vigorously. This is who we found, whose original color was clear and turned into milky white. At this time, the teacher opened the bottle cap and explained to us: "When calcium hydroxide comes into contact with the right amount of water, it will become limewater. This is due to the problem of the solution. I will tell you later. " Then the teacher explained to us, let us do the experiment, and told us to be careful not to touch the chemical reagents when doing the experiment.
In this class, xu teacher explained to us while sitting and demonstrating to us. We all listened with relish and watched intently, so that I not only learned chemistry knowledge, but also experienced it myself. I am really happy today!
Today, I did an interesting experiment-"magic salt water".
I first pour a large bowl of salt into the white porcelain bowl, and then pour a lot of tap water. I must remember that tap water must be covered with salt. Only in this way can salt be dissolved in brine. I brought an unused brush and a small white porcelain tea bowl, poured some hot water into it, and scalded the brush in hot water. I waited for half an hour, but the hair on the brush was loose. I waited another quarter of an hour, and all the salt melted into salt water. Later, I brought a piece of paper as white as snow, and when the preparations were done, I began to do important work. I picked up a clean brush and dipped it in salt water a few times. Then I wrote "It's going to rain" in big letters on white paper. After writing, I put the paper on the wall with scotch tape to dry. After drying, I saw nothing on it, so I went to play with confidence. When eating at noon, open the lid and the delicious pig's feet smell. I took a piece of white paper and put it on the pot. Four big words "It's going to rain" appeared in my IQ. Only then did I know that salt water would absorb water. Once the salt water absorbs water, the words written by the salt water will appear. Mom saw it and said in surprise, "Wow! It's amazing. "
This experiment is really interesting. I will do it next time.