This afternoon, the first class is science. We did an experiment. Metals expand when heated and contract when cooled.
Prepare for the experiment: a basin of water, copper rings, copper balls, alcohol lamps and lighters. The teacher first opened the lid of the essence lamp and lit the alcohol lamp with a lighter. Take the copper ring again and put the copper ball in the middle of the copper ring to see if it passes. The teacher said to us, "Did the copper ball pass the copper ring?" We said with one voice, "That's it." Then the teacher put the copper ball on the alcohol lamp and burned it. Ten minutes later, the teacher put the copper ball in the middle of the copper ring again, but the copper ball couldn't pass. The teacher put the copper ball into the basin again and heard a bang. The teacher put the copper ball in the middle of the copper ring, and the copper ball passed again. The teacher took the lid of the alcohol lamp and put it out obliquely. Everyone was puzzled, and the teacher explained, "The first copper ball just passed, and the second copper ball burned and heated on the alcohol lamp, and its volume expanded, so it couldn't pass." The third time, I put the copper ball in the water. When the water cools, the copper ball will shrink and can pass through. This is why metals expand when heated and contract when cooled. "The teacher also said," Besides copper, there are many other objects that expand when heated and contract when cooled. For example, thermometers are made by this principle. "This is really an interesting experiment. Not only do I know that metal shrinks when heated and cooled, but I also know that it is very useful.
Nature is a treasure house of knowledge. As long as you are willing to explore and think seriously, you can always get a lot of inspiration from it.
As soon as I walked into the classroom today, I saw an insulated water cup and a plastic water cup and thought, what are you doing today? The teacher came and solved the mystery in our hearts. The teacher said, "Let's do a little experiment today." We all craned our necks to see what tricks the teacher would play. The teacher first wrote two words "lose weight" on the blackboard and asked the fattest classmate in the class: "Do you want to lose weight?" Xiao Pang said he wanted to go. I thought, what does this have to do with the experiment?
After a while, the teacher said that whether you believe it or not, this bottle can make him lose weight without external help. Some people are dubious, some people don't believe it, and some people believe what the teacher said. The experiment has begun! The teacher carefully poured the hot water from the thermos into the plastic bottle first, and only heard the sound of running water, which soon filled it up and hot air came out from time to time. Then the teacher poured hot water back into the thermos, and a miracle happened! The bottle slowly became a slim girl like a big fat girl. Just as everyone was wondering, the teacher explained the principle to everyone one by one. The teacher said, "The hot water heats the air in the bottle, which makes the air volume expand. When the hot water is poured out from the heat source, the air temperature drops and the volume becomes smaller. If the bottle cap cannot be tightened to replenish the air, the plastic bottle will collapse."
There is so much learning in life! As long as we carefully observe and explore, there will be more discoveries!
Can a plastic bottle with a narrow bottle mouth "eat" twice as many eggs as a large bottle mouth? In order to find out this problem, Teacher Lu took us to do an interesting experiment in this science class-the egg was eaten by a bottle.
Start class. Teacher Lu is holding a transparent plastic bottle with a round egg in it. Wow! The students exclaimed.
"Students, do you know how this egg was put in?" As soon as this question was raised, it aroused the interest of the students and began to talk noisily. Just as everyone was in high spirits, the teacher picked up a boiled egg, carefully peeled off the hard shell by hand, and told the students: "The eggshell must be washed, and the broken egg white should be soaked in clear water." Pull the shell, teacher Lu prepares the experimental equipment. I watched it for a long time, and some monks were puzzled: What is Teacher Lu doing? Wondering, I only heard the voice "Be careful, classmates." "Pass"! Before the students could react, the eggs were "eaten"!
The students were full of doubts and then suddenly realized. It turned out that after the bottle was heated, the air inside expanded, and the eggs placed on it blocked the mouth of the bottle, so that the air in the bottle could not shrink freely. With such a hard force, the egg was sucked in.
The fourth grade experimental composition is 300 words. In today's composition class, the teacher said, "Let's do an experiment today."
As soon as the voice fell, the teacher turned on the computer and several words appeared on the screen: How many times can a piece of paper be folded in half?
The classroom suddenly exploded, and some students shouted, "It's that simple?" Some students said, "At least you can get a discount of 10." Some students shouted, "Haha, I can fold it a hundred times."
The teacher calmed everyone down and said to us, "In this case, please finish the experiment."
Bring me the paper. I can't wait to fold it in half. The first two times were simple, the third time gradually hardened, the fourth time the paper began to swell, and the fifth time the whole paper almost turned into iron ... things became more and more difficult. When I finished folding for the sixth time and planned to fold for the seventh time, I found that I couldn't fold it no matter how hard I tried.
Then the teacher spoke: "Please raise your hand if you have folded it ten times." No one in the class raised their hands, and the teacher smiled: "Who said that folding 100 times was not a problem just now?" Then he said, "How many times did you fold it?" We said in unison, "Six times." Then we all laughed.
This is really an interesting experiment, and it also makes me understand that if you haven't done it yet, don't jump to conclusions.
Teacher's comment: according to the order before and after the experiment, the experimental activities are described clearly, and the rich details make the composition wonderful!
Just after class today, the teacher asked us a question: "Does air take up space?" We all said, "No," said the teacher. Let's do an experiment to prove it!
First, the teacher prepared a basin filled with clear water, a glass and two pieces of paper. Knead two pieces of paper into a ball and put it in the glass for fear of falling out, then press it in hard, so that the glass mouth is close to the water surface first, and then suddenly press the glass down to the end, and then everyone can guess whether the paper is wet. Some students said they were wet, some students said they were not wet, and some students said they didn't know. The teacher asked us to have a look. She quickly lifted the cup and wiped the mouth and outside with a dry cloth. Let's each touch the paper with our hands to see if it is wet. We are all moved. The paper is not wet. We are confused. The water obviously reached the bottom of the cup. Why is the paper not wet? The teacher said that the air in the cup had not completely gone out when it was put into the water, so the air separated the paper from the water. At this time, the teacher asked loudly, "Does air take up space?" "Explain why." We answered with one voice.
After this experiment, I became interested in science and wanted to know more about the mystery of air in the future.
In today's composition class, the teacher gave us a question: Can a piece of paper be folded in half nine times? Hearing this topic, the classroom suddenly boiled.
Some students said, "Of course!" Some students said, "big paper is ok, but small paper is not." Some students said, "I don't think so." The teacher said, "Don't worry, let's do an experiment."
First, the teacher gives each group an a4 piece of paper, then one person folds it, one person takes notes and the others observe. When my deskmate folded it for me, I saw that the first time she folded it was as easy as blowing off the dust, but the more she folded it, the harder it became. She frowned when she folded it for the sixth time. I don't think she can hold on any longer. Sure enough, when she folded the card for the seventh time, she finally let go.
But she was not convinced, so she changed the folding method, folded the paper into a thin "noodle", then folded it in half, and then folded it in half. Finally, she happily held up a "bread roll" and said to the teacher, "I folded it eight times!" "
Seeing that time was running out, the teacher said, "It's time. Just now, a classmate said that a big piece of paper can be folded nine times. Teacher, here is one. I asked a classmate to fold it. " There were bursts of "I" voices in the classroom. My deskmate volunteered to give a demonstration and ended in failure.
The students used many strange methods, some folded like fans, some folded more than a dozen times, and some even bit with their teeth.
Another student came up with a new method-folding with tissue paper. Now you can finally fold it nine times!
This experiment is really interesting. I will do it again.
There are many TV programs I like to watch, but my favorite TV is open sesame, because it often shows us some experiments and tells us scientific truth. I imitate them, among which I like to do the experiment of "friction electrification" best.
I prepared a piece of paper first, cut it into many small pieces and put it on the table. Then bring a plastic pen and gently rub it back and forth on your hair. Put the pen in a piece of paper. These pieces of paper are attached to plastic pens. I shook it gently, and the paper seemed to be dancing. I think it is amazing. After repeated experiments, I still feel unsatisfied. "I have done so many experiments. What is its principle? " I thought to myself. It's dusk, but I still don't know how it works.
In the evening, I asked my mother for advice and asked why. My mother said to me, "The kind of experiment you just mentioned is because the plastic pen rubs the hair to generate static electricity and absorbs the small pieces of paper." For example, when the weather is dry, when you comb your hair or take off your sweater, you will also generate static electricity, hear crackles and even see the light of discharge. "After listening to my mother, I finally know the final answer of this little experiment.
By doing this experiment with my own hands, I understand that many natural phenomena in our real life contain a scientific truth. As long as we are good at observation and diligent in thinking, we will certainly know the mystery.
The fourth grade experimental composition is 300 words. In science class, we did an experiment about dissolution. The materials we prepared are: flour, soap bars, broken soap, hot water, cold water and five cups.
Let's take out a chopstick, several spoonfuls of flour and half a glass of water, then pour the flour into the quilt and stir it gently with chopsticks. After a while, we saw that the clear and transparent water gradually became turbid, gradually turned pale white, and finally became milky white. After careful observation, we found that the shadow of flour was gone. It is concluded that flour can be completely dissolved in water, making transparent water opaque and milky white.
Then, we use two cups instead of half a cup of hot water and cold water, and put two soaps of the same size at the same time. We observed that soap soaked in hot water changed rapidly. The soap in the hot water seems to be smoking. Milky soapy water diffuses upward from the bottom of the cup, the soap bars become smaller, and the water becomes turbid and milky. Second, a small amount of soap is dissolved in cold water, and the milky white is not obvious. We don't have to wait for the soap to completely dissolve, so we will come to the conclusion that soap dissolves faster in hot water than in cold water.
I think this is an interesting experiment.