Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Atomic were once thought to be fundamental pieces of matter, but they are in turn made of smaller subatomic particles. There are three major subatomic particles neutrons, protons, and electronic. Protons and neutrons can be broken into even smaller units, but these smaller units do not occur naturally in nature and are thought to only be produced in manmade particle accelerators and perhaps in extreme stellar events like supernovas. The structure of an atom can best be described as a small solar system, with the neutrons at the center and the electrons circling them in various orbits, just as the planets circle the sun .In reality, the structure of an atom is far more complex, because the laws of physics are fundamentally different at the atomic level than of the level of the observable word. The true nature of atomic structure can only be expressed accurately through complex mathematical formulas .This explanation, however, is of little use to most average people.
Protons and neutrons have nearly equal mass and size, but protons carry a positive electrical charge, while neutrons carry no charge at all. Protons and neutrons are bound together by the strong nuclear force, one of the four basic forces in the universe. Protons and neutrons give atoms some of their most basic properties. Elements are defined by two numbers; their atomic number , which is equal to the number of protons they have, and their atomic weight , which is equal to total number of their neutrons and protons. In most lighter atoms , the number of neutrons and protons is equal , and the element is stable. In heavier atoms, however, there are more neutrons than protons , and the element is unstable, eventually losing neutrons through radioactive decay until a neutral state is reached.
Electrons are negatively charged particles. They are bound to their atoms through electromagnetic attraction. Opposite electrical charges attract one another, so the positive charge of the proton helps keep the negatively charged electron in orbit around the nucleus of the atom. Electrons are different from neutrons in that they cannot be broken down into smaller particles. They are also far smaller and lighter than neutrons and protons. An electron is about one thousandth of the diameter of a proton and an even smaller fraction of its mass. Electrons circle the protons and neutrons at the center of the atom in orbit. These orbits are often called electron shells. The closer the orbit is to the center of the atom, the lower its energy is. There are seven electron shells, and each higher level can hold more electron than the previous shell. Electrons naturally seek to occupy the lowest shell possible .So if there is space in a lower shell, an electron will drop down to occupy that space. At temperatures higher than a few hundred degrees, electrons will gain energy and move to a higher shell, but only momentarily. When the electrons drop back down to their natural shell, they emit light .This is why fires and other very hot objects seem to glow.
Electrons are also primarily responsible for many of the chemical properties of atoms. Since electrons seek to occupy the lowest electron shell possible, they will move from one atom to another if there is a space available in a lower electron shell. For example, if there is an atom with an open space in its third shell, and it comes into contact with an atom with electrons in its fourth shell, the first atom will take one of these electrons to complete its third shell. When this happens, the two atoms will be chemically bonded to form a molecule. Furthermore, atoms sometimes lose electrons in collisions with other atoms. When it happens, the radio of protons and electrons in the atom changes, and therefore, the overall electrical charge of the atom changes as well. These atoms are called isotopes, and they have significantly different chemical properties from their parent atoms.
The phrase one another in paragraph 3 refers to
A. Particles
B. Electrical charges
C. Electrons
D. Atoms
Đáp án là B
Cụm từ “ one another” ở đoạn 3 ám chỉ đến
A. Các phân tử
B. Các điện cực
C. Các electron
D. Các nguyên tử
Dẫn chứng: Opposite electrical charges attract one another [ Những điện cực ngược nhau sẽ hút lẫn nhau]
Read the following passage, and mark the letter (A, B, C or D) on your answer sheet to indicate the correct answer for each of the blanks.
Many people love boats. Going out on the water on a warm summer day is a lot of (31) _______. (32) _______ , different people like different kinds of boats. Two of the most popular kinds of boat are sailboats and speedboats. Sailboats use the (33) _______to give them power. They only have small engines. In contrast, speedboats have large engines and go very fast. Furthermore, speedboats are usually not as (34) _______ as sailboats. Speedboats are small so that they can go fast. Sailboats, on the other hand, are big so that they are more comfortable. ( 35) _______, sailboats can travel into the ocean, but this would be very dangerous in a speedboat. You can only use speedboats on rivers or lakes
Điền vào ô số 34
Read the following passage, and mark the letter (A, B, C or D) on your answer sheet to indicate the correct answer for each of the blanks.
Many people love boats. Going out on the water on a warm summer day is a lot of (31) _______. (32) _______ , different people like different kinds of boats. Two of the most popular kinds of boat are sailboats and speedboats. Sailboats use the (33) _______to give them power. They only have small engines. In contrast, speedboats have large engines and go very fast. Furthermore, speedboats are usually not as (34) _______ as sailboats. Speedboats are small so that they can go fast. Sailboats, on the other hand, are big so that they are more comfortable. ( 35) _______, sailboats can travel into the ocean, but this would be very dangerous in a speedboat. You can only use speedboats on rivers or lakes
Điền vào ô số 32
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
This story has been passed down by ________of mouth
Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following sentences
It’s your duty to finish your homework before you go to school
Mark the letter A, B, C, or D on your answer sheet to show the underlined part that needs correction in each of the following questions
I have never dived in a twenty-metre-deep lake before, so I’m a bit afraid of doing it
Mark the letter A, B, C, or D on your answer sheet to show the underlined part that needs correction in each of the following questions
Not surprisingly, poverty is a problem worth of concern in every country
Read the following passage and circle A, B, C or D to indicate the correct answer to each of the question from 36 to 42
George Washington Carver showed that plant life was more than just food for animals and humans. Carver’s first step was to analyze plant parts to find out what they were made of. He then combined these simpler isolated substances with other substances to create new products.
The branch of chemistry that studies and finds ways to use raw materials from farm products to make industrial products is called chemurgy. Carver was one of the first and greatest chemurgists of all time. Today the science of chemurgy is better known as the science of synthetics. Each day people depend on and use synthetic materials made from raw materials. All his life Carver battled against the disposal of waste materials and warned of the growing need to develop substitutes for the natural substances being used up by humans.
Carver never cared about getting credit for the new products he created. He never tried to patent his discoveries or get wealthy from them. He turned down many offers to leave Tuskegee Institute to become a rich scientist in private industry. Thomas Edison, inventor of the electric light, offered him a laboratory in Detroit to carry out food research. When the United States government made him a collaborator in the Mycology and Plant Disease Survey of the Department of Agriculture, he accepted the position with the understanding that he wouldn’t have to leave Tuskegee. As an authority on plant diseases – especially of the fungus variety – Carver sent hundreds of specimens to the United States Department of Agriculture. At the peak of his career, Carver’s fame and influence were known on every continent.
With what topic is the passage mainly concerned?
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
I personally don’t believe you can ________of his support
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
Paul asked Maria to ________him to the dentist’s because he didn’t want to go by himself
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
One of the areas of multimedia that is growing quickly ________is sound
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
You will not be successful in business if you don’t ________risks
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions
She’s so depressed. All these problem are really ________.
Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions
Joan broke her right leg in the accident last week. Her parents worried a lot
Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions
The box was too heavy. John could not move it.
Mark the letter A,B,C, or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions
When she fell ill, her daughter took over the business