Tài liệu miễn phí Tiếng Anh phổ thông

6 Unit One SCIENCE Science (Latin scientia, from scire, “to know”), is the term which is used, in its broadest meaning to denote systematized knowledge in any field, but applied usually to the organization of objectively verifiable sense experience. The pursuit of knowledge in this context is known as pure science, to distinguish it from applied science, which is the search for practical uses of scientific knowledge, and from technology, through which applications are realized. Knowledge of nature originally was largely an undifferentiated observation and interrelation of experiences. ...

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English for students of Physics_Unit 2

21 Unit Two PHYSICS Physics is the major science dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces. Sometimes in modern physics a more sophisticated approach is taken that incorporates elements of the three areas listed above; it relates to the laws of symmetry and conservation, such as those pertaining to energy, momentum, charge, and parity. Physics is closely related to the other natural sciences and, in a sense, encompasses them. ...

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English for students of Physics_Unit 3

Chemical reactions occur continuously in the atmosphere, in factories, in vehicles, in the environment, and in our bodies. In a chemical reaction, one or more kinds of matter is changed into a new kind-or several new kinds-of matter. A few common chemical reactions are shown here. Life as we know it could not exist without these processes: plants could not photosynthesize, cars could not move, pudding could not thicken, muscles could not burn energy, glue could not stick, and fire could not burn. ...

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English for students of Physics_Unit 4

Unit Four International System of Units. reading passage. International System of Units. International system of unit is the name adopted by the Eleventh General Conference on Weights and Measures, held in Paris in 1960, for a universal, unified, self-consistent system of measurement units based on the MKS (meter-kilogram-second) system. The international system is commonly referred to throughout the world as SI, after the initials of Systome International. The Metric Conversion Act of 1975 commits the United States to the increasing use of, and voluntary conversion to, the metric system of measurement, further defining metric system as the International System of Units as interpreted...

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English for students of Physics_Unit 5

In physics, particles that cannot be broken down into any other particles are called elementary particles. The term elementary particles also is used more loosely to include some subatomic particles that are composed of other particles. Particles that cannot be broken further are sometimes called fundamental particles to avoid confusion. These fundamental particles provide the basic units that make up all matter and energy in the universe. Scientists and philosophers have sought to identify and study elementary particles since ancient times. ...

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English for students of Physics_Unit 6

Besides the blowing dust and the heavenly bodies, little else moves on the Martian landscape. This lack of movement might seem to be strangest of all, for we humans are used to motion. Almost from birth, infants follow motion with their eyes, and from then on we are continually aware of things moving about, starting, stopping, turning, bouncing. On earth we see liquids flowing, people moving, and the wind stirring the leaves of trees. Although we can not see them, we know that the very atoms and molecules of matter are continuously in motion. Even mosses and lichens that...

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English for students of Physics_Unit 7

There is no gravitational pull . . . only a push! This hypothesis provides a general model for the mechanics of gravitation. It in no way refutes the observed behavior of gravitation, but merely seeks to explain it. I have based all but a single aspect of this model on established scientific knowledge, and that single aspect is my prediction of an unknown. (So it remains to be proved or disproved.) The team of medieval physicists stepped out of the time machine and began to examine the strange, new device fastened to the window. They had never before seen a...

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English for students of Physics_Unit 8

We mentioned compounds of calcium, lithium, and strontium without specifying which compounds we were talking about. This may have given you the impression that only the spectrum of one of the elements in a compound can be observed. It is true that the flame of your alcohol burner is hot enough to produce the spectra of sodium, lithium, calcium, copper, and a few other elements, but that is not hot enough to produce the other spectra of elements, such as oxygen and chlorine. However, if we heat a sample of a compound to a sufficiently high temperature (for example,...

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English for students of Physics_Unit 9

Perhaps nothing is so ingrained in our senses as the perpetual pulling of the earth on our surroundings. It’s always there, never changing. It’s been hugging solids, liquids and gases to the earth’s surface for over 4 billion years. Earth’s gravity is built into our descriptions of our world with words like up, down, and weight. Exactly what is weight? A weight is a force, nothing more. Your weight is the pull of earth’s gravity on your body. Likewise, the weight of your car is the force of the earth’s attraction for it. The greater the mass is, the...

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English for students of Physics_Unit 10

Toss your keys along the floor, they’ll skitter along for a bit as friction does negative work on them, reducing their kinetic. Quickly, the keys come to rest, and the kinetic energy you gave them is gone. But in this case they can’t turn around (as they did when you picked them up), gather speed from the same frictional force that acted to slow them, and jump back into your hand with the same kinetic energy. Once the motion stops, the friction stops, and it can not restore the kinetic energy of the keys as gravity is able to...

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English for students of Physics_Unit 11

Science tries to explain a very complicated world. We are surrounded by very many objects, moving around, reacting together, breaking up, joining together, growing and shrinking. And there are many invisible things, too - radio waves, sound, ionizing radiation. If we are to make any sense of all this, we need to simplify it. We use models, in everyday life and in science, as a method of simplifying and making sense of everything we observe. A model is a way of explaining something difficult in terms of something more familiar. For example, there are many models used to describe...

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English for students of Physics_Unit 12

Scientists still do not know exactly what causes the earth’s magnetic field. In the 16th century, it was believed that a mountain of magnetite (a magnetic mineral) was located at the North Pole and that this mountain caused the earth’s magnetic field. English physician William Gilbert was the first to propose, in 1600, that the earth itself was a massive magnet. Current theories hold that the earth’s magnetic field is created by currents within the liquid outer core of the earth, which is composed mostly of iron. This liquid core contains ions, or electrically charged atoms and molecules. The...

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English for students of Physics_Unit 13

The solid state and the structure of Solids We all live on terra firma, the 29 percent of our planet’s solid crust that lies above sea level. And almost everything we do is tied to solids, living in houses, creating and marketing solid goods, eating solid foods, and so on. But if you are asked to define a solid, it might be difficult. A solid is one of those familiar things that are hard to put into words. A good definition of a solid is that it tends to keep its shape when it is left alone. But that doesn’t...

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English for students of Physics_Unit 14

Electric charge and a measure for the quantity of charge Any household electrical appliance – be it a light bulb, a motor, or a television set – has two contacts which have to be plugged in to get the device to operate. This common characteristic, that an electrical apparatus must have two wires connecting it to a source of electricity, gave the rise in the eighteenth century to the idea that when an electrical device is working, something is moving through it. That something is called electric charge. When you pull out a plug, turn off a switch, or disconnect...

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English for students of Physics_Unit 15

In both fission and fusion, unstable nuclei have become more stable. Energy is released. In order to explain these processes, we need to be able to say where this energy comes from. One answer lies in the origins of the nuclei we are considering. Take, for example, uranium. The earth’s crust contains uranium. In some places, it is sufficiently concentrated to make it worth while extracting it for use as the fuel in fission reactors. This uranium has been part of the Earth since it was formed, 4500 million years ago. The Earth formed a swirling cloud of dust...

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List of homonyms - Bảng những từ đồng âm

Tài liệu tham khảo rất hay và bổ ích về List of homonyms - Bảng những từ đồng âm dành cho những bạn yêu thích học môn tiếng Anh. Tài liệu liệt kê đầy đủ tất cả các từ đồng âm trong tiếng anh giúp bạn bổ sung thêm vốn từ vựng tiếng của mình. Mời các bạn cùng tham khảo học tập.

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5 đề thi học sinh giỏi môn tiếng Anh lớp 9 và đáp án

ĐỀ THI CHỌN HỌC SINH GIỎI LỚP 9 – THCS Môn thi: Tiếng Anh Thời gian: 150 phút ( Không kể thời gian giao đề ) §Ò Sè

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