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If you are looking to get a better understanding of the world around you, chemistry may be the perfect subject to study. It's a study of matter and its properties—— ways in which it behaves in special conditions and how it interacts with everything around it. At the heart of all the discoveries, such as medicine, cooking, and several other areas, is one important table that organises elements based on their atomic number and chemical properties; the periodic table(元素周期表). 

Although the first periodic table was published in1869. it was a work in progress for hundreds, if not thousands of years. 

Since ancient times, people have been interested in elements such as gold, tin, iron and copper(which are written as Au, Sa, Fe and Cu in the table) in their natural forms. They were dug up from the ground and used to make jewelry, guns, coins and many other things. Over time, people became more curious about these metals and how they were made up. In ancient Greece, Aristotle and other philosophers said things were made from the elements of earth, water, fire and air. For years, this idea was accepted, Then people began to consider this idea again during the Age of Enlightenment. 

In 1661, British scientist Robert Boyle described an element as something that" cannot be broken down into a simpler matter by a chemical reaction". Over a century later, Antoine-Laurent de Lavoisier, Father of Chemistry, published the first modern textbook on chemistry. In it, he listed some matter which he believed should be divided as elements into two groups: metals and non-metals. Although his work wasn't completely correct, it represented a big step forward at that time. 

Over the next century, scientists started to divide the elements into different groups depending on their properties and atomic weights. However, it is Russian chemist Dmitri Mendeleev who is usually believed as the first person to make a periodic table. Although other scientists had handed in tables, they were finally refused by the scientific community because they were short of details. Mendeleev put all of the elements in a proper order according to their atomic mass. He was even smart enough to leave empty spaces for elements which hadn't been discovered at that time, Although Mendeleev's periodic table wasn't perfect, it set the way or the order that is similar to the one used today. 

Sports provide a great way to understand something about physics , Physics is the study of matter, motion(运动), force(力) and energy. And since sports like soccer, swimming and cycling include bodies moving through space, they can help us understand how physics works. 

Imagine that you' re looking at a soccer ball on a grassy field. If you do nothing to the ball, it will stay motionless on the grass. If you kick the ball, it will roll along the grass before coming to rest again. Pretty simple, right?

For thousands of years, though, people thought that objects like this soccer ball came to rest because they had a natural tendency to stop. It took a famous physicist called Sir Is age Newton, who lived in the1600s, to prove that this was not exactly correct. 

Newton suggested that objects like the soccer ball have a natural tendency to keep moving. The only reason they stop, he believed, is because an unbalanced force acts on them. By an unbalanced force, Newton meant the force is given to the soccer ball by its environment. When kicked, the surface(表面) of the ball travels over the grass. creating friction(摩擦力). The taller the grass and the rougher(粗糙) the surface of the ball, the more friction is created. And the more friction between the ball and the grass, the less it will travel after being kicked. 

Now, imagine that there is no grass. Instead, the ball is resting on a frozen lake. When you kick the ball on the ice, the ball will go much farther than it would have on the grass. This is because ice provides a lot less friction than the grass. 

Even so, ice does cause some friction and that will make the ball come to rest again. But now imagine that instead of ice, the ball is in a place where there's no friction at all. The ball is floating(漂浮) in a vacuum(真空). If you remove friction entirely, kicking the soccer ball would cause it to keep going and going at the same speed, until some force causes it to slow down and stop. To explain Sir Isaac Newton's idea in a simple way, a soccer ball on the grass will stay where it is unless a force acts on it. Similarly, once you kick the ball, it will remain in motion unless acted on by force, This, in so many words, is known as Newton's First Law of Motion. 

①"A friend in need is a friend indeed. " Friends are important to us. Friends help us get through hard times. Friends also influence us a lot. Let's enjoy two poems about friendship. 

④Both poems are famous in their cultures, but they tell different stories. Li Bai described the scene(场景) of his friend seeing him off. The US poet Robert Frost wrote about a friend's visit when he was working, Li made a comparison. His poem shows the friendship between his friend and him is deeper than the deep water. While Frost's poem tells the readers that we should stop what we are doing to talk with our friends. It tells us that nothing should get in the way of spending time with friends. The language is simple but sincere. 

Glaciers(冰川) hold about 70% of the earth's fresh water. They are large pieces of closely packed ice and snow. Glaciers only form in places where it is very cold. Every year, new snow falls on top of the old snow. The layers(层) of snow press down on each other, and then the snow crystals(晶体) start to change. They get smaller, and air pockets are pushed out of the snow. This allows the crystals to grow longer. Over time, the snow layer at the bottom of all the other snow layers becomes ice. The whole process of making a glacier takes about 100 years. 

Some ice is packed so closely that it looks like it is blue. The snow on top of a glacier looks white because it reflects all of the light. But the ice layers of the glacier do not have many air pockets. They absorb different parts of light and reflect blue light. 

Some of the glaciers on the earth may be very old. Scientists think that a few glaciers have ice that is about 8 million years old. Not all of the glaciers are that old, though, A number of glaciers in Alaska are only about 100 years old. 

There are different kinds of glaciers. An ice stream is a kind of glacier that forms on another glacier, and it looks like a frozen river. Rock glaciers are made when ice, rock and other objects get mixed together. 

Just one bite of the cake with eggs is enough to make John feel very sick. Susan gets a terrible skin problem whenever she has seafood, and David nearly died when he first ate a peanut cookie. The body's reaction(反应) to certain foods can be quite serious resulting in breathing problems or even the death. There are many things we eat that may cause our bodies to react badly if we have a food allergy(过敏). 

There are three common ways to test food allergies. Probably, the simplest way is to give a child a food test. The doctor watches the child eat a little certain food to see if the child has an allergic reaction. This method takes quite a long time, so it is used less often than the other two methods-skin tests and blood tests. In a skin test, a doctor puts allergens under the child's skin and then waits to see if the child's skin reacts. In a blood test, doctors take some of the child's blood and add allergens to it and then check the blood. 

Dr. Jennifer from Stanford University spent 10years studying the methods. She found a surprising fact. Skin tests or blood tests given to patients who visited their doctors for treatment of skin problems or stomachaches showed that these patients were allergic to certain foods. However, later tests showed that although they tested positive(阳性), fewer than 50percent of them actually had food allergies. The problem might be food intolerance(不耐受) instead of a food allergy. 

Food allergies have something to do with a person's immune system, while food intolerance has something to do with a person's digestive system and the reaction is usually less serious. One of the most common kinds of food intolerance happens to people who have trouble taking in the milk sugar in food like milk, cheese and ice cream. 

Though allergy tests may show false positive results, they are still useful and can save lives. Some children's food allergies may disappear as they grow older. So even though doctors don't cure food allergies. sometimes the body itself does. 

The Zenghouyi Chine Bells(编钟) were uncovered from the Zenghouyi Tomb in Suizhou, Hubei Province in1978. They are historically important treasures of China. The Zenghouyi Chime Bells are hung at three levels and are set in eight groups. There are 19 bells in three groups at the top level, 33 bells in three groups at the middle level and 12 bells in two groups at the bottom level. Besides, there is a much larger bell used to adjust pitch(调节音高), The bells in each row are different from one another in shape and size. 

The Zenghouyi Chime Bells are hung on two sets of wood racks(架子). One rack is 7. 48 meters long and2. 65 meters high. The other rack is 3. 35 meters long and 2. 73 meters high. The two racks are perpendicular to each other, which forms an angle of ninety degrees. 

The Zenghouyi Chime Bells weigh a total of about4. 4 tons. The biggest bell is of 153. 4 cm in height and203. 6 k g in weight while the smallest bell is of 20. 4 cm in height and 2. 4 kg in weight. 

Five musicians were needed to play the instrument in the past. These bells have no clappers(铃舌) and are sounded by striking. Because of their shape, each bell could produce two different tones(音色)— One if struck at the side, the other at the center. The whole set of chi me bells is able to produce all the tones of a modern piano. 

You may feel that math is hard and boring. Is it possible that you' ve been looking at math in the wrong way? With the International Day of Mathematics coming on March 14th, we interviewed Li Xing, a math professor at Ningxia University. We asked if math can be beautiful and fun. Here's what he said. 

Numbers are beautiful.

Many people today want to have beautiful looks. But there is math hidden in beautiful human bodies, Measure(测量) the length from your head to your belly button(肚脐) and from your belly button to your feet. If the ratio(比例) of these two numbers is around0. 618, it is the golden ratio, which can be seen everywhere, like in nature, music and paintings. 

In Chinese poems, we can also see the beauty of numbers. As Li Bai wrote, "I' ve sailed a thousand miles through Gorges in a day(千里江陵一日还)", "My skiff has left ten thousand mountains far away(轻舟已过万重山)". "A . thousand miles in one day", "ten thousand mountains"— All these numbers show how fast Li Bai traveled and how happy he felt. Numbers give us freedom to imagine. 

Carves(曲线) are beautiful.

Sine(正弦) curve is beautiful. It goes towards the two opposite directions on and on without ever ending. When you look at it, you may feel like standing by the sea and watching the waves slowly moving. The tangent(正切) curve is like a waterfall. That's really "dashing down three thousand feet from high(飞流直下三千尺)". If you do a math problem and get that curve, you' ll feel wonderful. 

Formulas(公式) are beautiful.

There are many amazing formulas. For example, in a right triangle(直角三角形), the square of the longest side is equal to the sum of the squares of the other two sides. How neat(简洁的)! Just as the Chinese-American mathematician Chern Shing-shen said, "Math is fun!"

写作要求：

1.短文内容积极向上，须包含思维导图里的所有信息，可适当拓展；

2.文中不能出现真实的人名或校名。

My Chinese Learning

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Jianzhi is a traditional style of paper cutting in China. It has been a symbol of Chinese culture hundreds of years. In the (six) century, people started to practice jianzhi in China. Jianzhi has a number of special uses in Chinese culture. Almost all of them are for health, happiness or peace. Red is used the most (common) among all the colors. Since long ago, Chinese people have been (interest) in cutting paper into traditional Chinese characters to symbolize the Chinese zodiac (生肖) (animal).

Paper cutting is popular around the world, only the Chinese paper cutting is listed in the UNESCO Intangible Cultural Heritage Lists (联合国教科文组织非物质文化遗产名录). The Chinese paper cutting gets (it) place because it has a history of more than 1,500 years and it (tell) so much of Chinese history and culture.

Paper cutting has (develop) fast over the years. Paper cutting is still popular in China, especially during special festivals like Spring Festival. They are often seen at Chinese weddings as well.

We should learn English well, we can tell Chinese stories in English to the world.

No matter how hard your situation is, you not lose heart.

This dictionary is than you think.

important role parents play in shaping children's future!

in the library.

During the years, people change a lot. Five years is enough to compare yourself now and then. I think that I have changed a lot in the past five years.

Firstly, there are changes in my thoughts. Five years ago my thoughts were the same as a child's. I believed that the world was a place without problems. I thought that I could always have time for games and friends wouldn't change. Also I was sure that if I had any problems, my parents could always be around me, offering help. Now I still believe that the world is a great place to live in, but sometimes there are different problems you have to face. And at times you have to deal with these problems alone without any help. And that is one of the changes that have happened to me in the past five years. Now I'm much more responsible (有责任的) and serious than five years ago.

Secondly, there are some changes in my interests. Now I spend less time with friends and I spend most of my time studying for exams. Five years ago, it wasn't so. I believed that there was nothing more important than watching cartoon movies during those days.

Although I have changed in some ways, there are some similar ways between now and then. For example, I still like spending time with friends. And I am still sure that childhood is the best time in our life.

According to a report from WHO, people around the world are getting fatter. Over one billion people are overweight and the number is still increasing.

Overweight does harm to people's health and it is a major risk factor for a number of diseases, including diabetes (糖尿病), cardiovascular (心血管的) diseases and cancer.

Here are five drinks that can help you lose weight.

◆Detox Juices (排毒果汁)

Detox juices are easy for you to make in your kitchen. Drinking detox juices is the fastest and most natural way for you to lose the extra pounds.

◆Vegetable Juices

Vegetable juices, on the other hand, can also benefit your weight in the long run. They can balance the hormone (激素) levels in your body.

◆Green Tea

Although green tea will only help you lose a few pounds, it's good for you to reduce stress and relax better.

◆Fruit Juice—Cranberry and Pear

Fruit juices are delicious, easy to prepare and very rich in nutrients, vitamins and minerals. Among the fruit juices, pears and cranberries are the most delicious and most efficient for you to lose weight.

◆Black Coffee

Black coffee can help you lose weight. But don't have black coffee with milk or sugar, or you will get more calories.

A. People have drunk green tea for hundreds of years.

B. Tea was first discovered and drunk by Chinese people.

C. There are many ways to overcome this health problem.

D. And it can also lower the risk for cancer as well as heart disease.

E. At the same time, they can also make you look younger and beautiful.

F. You can make them out of fruits or vegetables or by combining these two.

When you want to buy a pair of running shoes, will you choose Nike or Li-Ning? It's a choice between local and foreign brands. According to a latest study, Chinese people generally prefer local brands to foreign brands. They choose the local brands because of the low price, good quality (质量) and creative design (设计).

Some Chinese brands have risen in these years. They have even started to win some fans abroad. A research showed that 71 percent of customers said Chinese brands were important to them.

Chinese brands like Huawei, Xiaomi, DJI, Feiyue, Li-Ning and Shein have all become more popular abroad. For example, Huawei is the world's second-biggest mobile phone company. Its products are used in more than 170 countries and areas. Huawei is also a leader in 5G technology. Shein, a "fast fashion" brand, made more than 10 billion dollars last year, a 100-percent increase over 2019, Global Times reported. Many European people like Shein products because they're affordable, fashionable and of high quality.

In the future, Chinese brands will continue to develop. "Thanks to a bigger market, improved supply chains (供应链) and efficient (高效的) producing, this is the best time for the development of local brands," Yan Qiang, a partner with Beijing-based Hejun Consulting, told Global Times.

It's important to teach your children good manners (礼仪). Teaching good manners should begin long before they know how to walk or talk. In life, you have to set a good example for them.

But how do we teach them good manners? There is a good book, How to Behave and Why. It is written by Munro Leaf. I read it with my first grade students and we love the book. It tells good manners that every child should know. The words in the book are not difficult and there are pictures in it. They make the book easy to understand.

Also, you can teach your children in life. Before they're going to school or a friend's house, tell them the importance of good manners. In your family, you can make a list of family manners. This helps children learn good manners anytime. And you can have a manners competition. It makes learning manners more interesting.

What are good manners for children? At school, they should respect (尊敬) teachers and other classmates. They shouldn't be noisy in class. And they should say "hello" or "goodbye" to teachers and classmates, and "thank you" when they get help from others. Good table manners are important, too. For example, teach your children not to talk with their mouths full. Tell them that old people should eat first. Teach your children not to be late for classes, parties, meetings and so on.

In fact, good manners will provide a lot of help for your children in their daily life. So teach them to your children and learn with your children.