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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 from 36 to 42The ability to conduct electricity is one of the key properties of a metal. Other solid materials such as silicon can conduct electricity but only effectively at certain temperatures. Also, some substances such as salt (sodium chloride) can conduct when molten or when dissolved in water. The ability of metals to conduct electricity is due to how...
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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 from 36 to 42

The ability to conduct electricity is one of the key properties of a metal. Other solid materials such as silicon can conduct electricity but only effectively at certain temperatures. Also, some substances such as salt (sodium chloride) can conduct when molten or when dissolved in water. The ability of metals to conduct electricity is due to how their atoms bond together. In order to bond together the metal atoms lose at least one of their outermost electrons. This leaves the metal atoms with a positive charge and they are now strictly ions. The lost electrons are free to move in what is known as a sea of electrons. Since the electrons are negatively charged they attract the ions and this is what keeps the structure together.

 An electric current is a flow of charge and since the electrons in the sea of electrons are free to move they can be made to flow in one direction when a source of electrical energy such as a battery is connected to the metal. Hence we have an electric current flowing through the wire, and this is what makes metals such good conductors of electricity. The only other common solid conducting material that pencil users are likely to encounter is graphite (what the „lead’ of a pencil is made from). Graphite is a form of carbon and again the carbon atoms bond in such a way that there is a sea of electrons that can be made to flow as an electric current. Likewise, if we have an ionic substance like salt we can make the electrically charged ions flow to create a current but only when those ions are free to move, either when the substance is a liquid or dissolved in water. In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow.

 Electrical insulators are substances that cannot conduct electricity well either, because they contain no charged particles or any charged particles they might contain do not flow easily. Water itself is a poor conductor of electricity as it does not contain a significant amount of fully charged particles (the ends of a water molecule are partly charged but overall the molecule is neutral). However, most water we encounter does contain dissolved charged particles, so it will be more conductive than pure water. Many of the problems that occur when touching electrical devices with wet hands result from the ever-present salt that is left on our skin through perspiration and it dissolves in the water to make it more conductive.

By Helena Gillespie and Rob Gillespie. Science for Primary School Teachers. OUP

According to the passage, a metal can conduct electricity due to ______.

A. the way its atoms bond together

B. the absence of free electrons

C. its atoms with a positive charge

D. the loss of one electron in the core of its atoms

1
6 tháng 10 2017

Đáp án A

Theo bài đọc, kim loại có thể dẫn điện là do

A. cách mà các phân tử kết hợp với nhau

B. sự thiếu các electron tự do

C. các nguyên tử của nó với cực dương

D. mất 1 electron trong nhân của nguyên tử

Dẫn chứng:The ability of metals to conduct electricity is due to how their atoms bond together

25 tháng 8 2018

Đáp án: C

7 tháng 10 2019

Đáp án: B

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 following questions. Television is one of man’s most important means of communication. It brings events and sounds from around the world into millions of homes. A person with a television set can sit in his house and watch the President making a speech or visit a foreign country. He can see a war being fought and watch statesmen try to bring about peace. Through...
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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 following questions.
Television is one of man’s most important means of communication. It brings events and sounds from around the world into millions of homes. A person with a television set can sit in his house and watch the President making a speech or visit a foreign country. He can see a war being fought and watch statesmen try to bring about peace. Through television, home viewers can see and learn about people, places, and things in faraway lands. Television even takes its viewers out of this world. It brings them coverage of America’s astronauts as the astronauts explore outer space. In addition to all these things, television brings its viewers a steady stream of programs that are designed to entertain. In fact, TV provides much more entertainment programs than any other kinds. The programs include action-packed dramas, light comedies, sporting events and motion pictures.
1. According to the passage, what does television bring us?

A. noise from around the world​

B. man’s most important means of talking

C. events and sounds from around the world​

D. president making a speech

2. According to the passage, what don’t entertainment programs include?

A. dramas​

B. news​

C. motion pictures​

D. comedies

3. According to the passage, which of the following is NOT true?

A. Television can bring us entertainment.​

B. Television can take us out of this world.

C. Television can help us widen our knowledge.

D. Television can help us make money.
4. The word “provides” in the second paragraph is best replaced by ________.

A. supplies​

B. divides​

C. admires​

D. separates

0
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 following questions.  Television is one of man’s most important means of communication. It brings events and sounds from around the world into millions of homes. A person with a television set can sit in his house and watch the President making a speech or visit a foreign country. He can see a war being fought and watch statesmen try to bring about peace. Through...
Đọc tiếp

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 following questions.
 Television is one of man’s most important means of communication. It brings events and sounds from around the world into millions of homes. A person with a television set can sit in his house and watch the President making a speech or visit a foreign country. He can see a war being fought and watch statesmen try to bring about peace. Through television, home viewers can see and learn about people, places, and things in faraway lands. Television even takes its viewers out of this world. It brings them coverage of America’s astronauts as the astronauts explore outer space. In addition to all these things, television brings its viewers a steady stream of programs that are designed to entertain. In fact, TV provides much more entertainment programs than any other kinds. The programs include action-packed dramas, light comedies, sporting events and motion pictures.

1. According to the passage, what does television bring us?

A. noise from around the world​

B. man’s most important means of talking

C. events and sounds from around the world​

D. president making a speech

2. According to the passage, what don’t entertainment programs include?

A. dramas​

B. news​

C. motion pictures​

D. comedies

3. According to the passage, which of the following is NOT true?

A. Television can bring us entertainment.​

B. Television can take us out of this world.

C. Television can help us widen our knowledge.

D. Television can help us make money.

4. The word “provides” in the second paragraph is best replaced by ________.

A. supplies​

B. divides​

C. admires​

D. separates

1
1 tháng 3 2022

29. According to the passage, what does television bring us? A. noise from around the world​B. man’s most important means of talking C. events and sounds from around the world​D. president making a speech

30. According to the passage, what don’t entertainment programs include? A. dramas​B. news​C. motion pictures​D. comedies

31. According to the passage, which of the following is NOT true? A. Television can bring us entertainment.​B. Television can take us out of this world. C. Television can help us widen our knowledge. D. Television can help us make money.

32. The word “provides” in the second paragraph is best replaced by ________. A. supplies​B. divides​C. admires​D. separates

22 tháng 4 2019

Đáp án: D

5 tháng 10 2017

Đáp án: C

Giải thích: Dẫn chứng nằm ở 2 dòng cuối của đoạn 1.

17 tháng 8 2018

Đáp án B

Kiến thức: Đọc hiểu

Giải thích:

Ý chính của đoạn cuối cùng là gì?

  A. Các nhà khoa học nghiên cứu về lão hóa đã kiểm soát quá trình lão hóa.

  B. Các nhà khoa học nghiên cứu về lão hóa đang làm việc chăm chỉ để giúp mọi người sống lâu hơn và khỏe mạnh hơn.

  C. Các nhà khoa học nghiên cứu về lão hóa đang cố gắng mang lại cho con người một cuộc sống vĩnh cửu.

  D. Các nhà khoa học nghiên cứu về lão hóa hiện có thể làm chậm quá trình lão hóa.

Thông tin: They are trying to discover how this clock works so that they can slow down the process. This could give man a longer life and a great number of productive years.

Tạm dịch: Họ đang nỗ lực tìm ra cách mà chiếc đồng hồ này hoạt động để có thể làm chậm đi quá trình này. Điều này có thể giúp cho con người sống lâu hơn và có được những năm tháng đóng góp nhiều hơn. 

22 tháng 8 2019

Đáp án: D

26 tháng 9 2019

Đáp án: D

Giải thích: Mấu chốt của câu này là các em phải đọc hết đoạn cuối để suy ra cái mà tác giả muốn hướng tới: Con người phải đối mặt với sự lựa chọn khó khăn: sự sống của mình hay cứu lấy động vật.

30 tháng 12 2018

Đáp án: A