One day in the summer of 2005, I stayed at home leisurely and felt bored, so I found a convex lens and began to play. Enlarge the chlorophytum for a while and turn it into a huge grass; Then I enlarged the little fish and turned it into a huge "shark" ...

Soon, I got tired of playing, so I put the convex lens on the table. After a while, my mother came to see me. After seeing the convex lens on the table, she quickly put it away and said to me, "Dongdong, don't put the convex lens in direct sunlight in the future, it will catch fire easily!" "

Hearing this, I thought to myself, why can a convex lens make an object catch fire? I asked, "Mom, how can a convex lens set an object on fire?" Mother replied, "Because convex lenses can concentrate light, sunlight can be regarded as parallel light. After the parallel light passes through the convex lens, it will converge to one point, which is the focus. This generates a lot of energy, and when it reaches a certain temperature, it can burn flammable objects. "

After listening to my mother, I was a little dubious. So I decided to do an experiment by myself!

I lay the paper flat on the ground first, and then focus the light on the paper with a convex lens. But just don't listen to me. I tried to get it together, but it spread out like a broom. However, I am very patient. I lean a little to the left and a little to the right. Finally, I succeeded in gathering the sunlight into a small light spot. Paper hasn't been burned for a long time, I think, is it because the sun is not hot enough? So I touched the paper with my hand, wow! I almost burned my hand.

I have to go home first. Later, I found out from the book: "white objects are easy to reflect light, and black objects are easy to absorb light!" " "

I was so happy that I decided to do the second experiment with black paper. Like the first experiment, I first laid the paper flat on the ground, and then skillfully adjusted the angle to the best position to turn the sunlight into a small spot. I waited for a while, and the paper really burned.

I finally understand: it turns out that the sun can really burn the paper together, but it takes some time. My mother also told me why it took some time to burn it. It turns out that this object will not burn until it reaches the ignition point.

I think if I forget to bring matches when I go out for a picnic in the future, I can make a fire with a convex lens.

Ah! I finally understand why a convex lens can make an object catch fire.

Why didn't the loach die?

In science class, the teacher gave each of us an assignment to make an ecological bottle, that is, "put a small amount of plants, animals that feed on these plants and other abiotic substances into a closed bottle to form an artificial simulated microecosystem." I was very interested in this experiment as soon as I heard it, so I found an empty oil pan, cut off the upper part, washed it, filled it with water, put a layer of silt on the bottom of the water, put some duckweeds on the surface of the water, and then put some small loaches I bought into the water. They got into the mud at once and came out for air every once in a while, making a pot of water muddled. It was really naughty.

In the first few days, I was very enthusiastic and observed several times a day, but gradually, with new experiments, I forgot. After a long time, a classmate talked about his environmental protection bottle, and it suddenly occurred to me that I haven't observed my environmental protection bottle for a long time. I think my poor loach must be dying of thirst. After school, I hurried home, put down my schoolbag and went to see my environmental protection bottle. I was shocked when I saw it. There is almost no water in the bottle, and there is no shadow of loach. I think the loach must be dead. Just when I was sad, suddenly, I saw bubbles on the muddy water. It won't be blown out by loach, will it? I quickly found a small stick and dug out the mud. Hey, a loach is coming out. "Ah, the loach is still alive, and the loach is still alive." I cried with joy. But I was surprised and asked my mother why loach could survive without water. Mom smiled and shook her head, so I had to go to the computer for help.

After searching the information, I finally understand that loach leaves water, lives in mud and breathes through intestines. Its intestine is connected with esophagus and anus, forming a short straight tube. Intestines are covered with many capillaries, which can absorb oxygen in the air. When it breathes through the intestine, gases such as carbon dioxide are discharged from the anus like "fart", so many bubbles often appear in the mud.

Oh, I see. No wonder loach didn't die in the mud without water. I'm so happy, because of my carelessness, I accidentally acquired this knowledge of loach.

Why does my kitten eat grass?

My mother bought me a kitten the other day. It's beautiful and lovely. My whole family loved it.

I often hide my pocket money secretly and buy dried fish in small shops. When I came back, I gave the dried fish to my kitten. The kitten ate quickly, ate a dried fish at once, and then climbed up the tree happily. Meow meow, I gave it another dried fish, and the kitten ate it quickly. The next morning, I saw the kitten curled up in a corner, still shivering. I thought it was hungry, so I quickly gave it a dried fish, but the kitten didn't eat it and still lay there, motionless. I went to school. At school, I was very sad and emotional, always worried about the kitten at home. Finally, after school, I hurried home, only to find that the kitten was eating a grass whose name I didn't know. Cats also eat grass? I can't believe it. Suddenly, the cat spit out the dried fish. I thought cats had food poisoning, so ask my mother quickly. My mother said, "Look for a hundred thousand reasons!" "I immediately checked and finally realized that cats can heal themselves. It eats grass to cure food poisoning. I am very happy. I not only solved a problem, but also understood a truth: when I encounter problems I don't understand in my life, I should look up more information and solve them with my own practical actions.

Introduction to primary school students: Huang Jiaping, 10 years old, male, likes painting, reading and doing scientific research.