K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

Question 8. A material which is NOT an electrical insulator _______.10 điểm  

 A. does not allow electricity to pass through it easily   

B. does not allow heat to travel through it easily   

C. allows heat to travel through it easily   

D. allows electricity to pass through it easily   

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                                The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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...
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                               

The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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 are 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. Freshwater Aquarium Fish

Playlist Freshwater Aquarium Fish

       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 or 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 Teacher. OUP

Which of the following is NOT true according to the passage?

A. . Pure water is much more conductive than most water we encounter every day. 

B. Graphite is a common solid substance that can conduct electricity. 

C. Salt can conduct electricity when it is molten or dissolved. 

D. Some materials are more conductive than others.

1
19 tháng 1 2018

Đáp án : A

Dòng 5 đoạn cuối: most water we encounter does contain dissolved charged particles, so it will be more conductive than pure water -> nước chứa các phần tử mang điện không hòa tan dẫn điện hơn nước nguyên chất

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                                The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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...
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                               

The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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 are 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. Freshwater Aquarium Fish

Playlist Freshwater Aquarium Fish

       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 or 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 Teacher. OUP

Salt in its solid state is not able to conduct electricity because                    .  

A.  it has free electrons

B.  its charged ions can flow easily 

C. it cannot create any charge ions

D. it charged ions are not free to move

1
17 tháng 3 2019

Đáp án : D

Cuối đoạn 2: In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow.

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...
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 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

 

 

 

 

Which of the following is NOT true according to the passage?

A. Graphite is a common solid substance that can conduct electricity

B. Salt can conduct electricity when it is molten or dissolved

C. Pure water is much more conductive than most water we encounter every day

D. Some materials are more conductive than others

1
15 tháng 3 2018

Đáp án C

Câu nào không đúng theo như bài đọc?

A.Than chì là chất rắn phổ biến có thể dẫn điện.

B. Muối có thể dẫn điện khi nó nóng chảy hoặc hòa tan

C. Nước tinh khiết dẫn điện tốt hơn hầu hết nước mà chúng ta gặp phải mỗi ngày.

D. Một số chất dẫn điện tốt hơn những chất khác.

Dẫn chứng: 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).

IV. Choose the word (A, B, C or D) that best fits the blank space in the following passage. (1,5 pt)     The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many university and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they...
Đọc tiếp

IV. Choose the word (A, B, C or D) that best fits the blank space in the following passage. (1,5 pt)

     The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many university and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became (4)________. In the 1980s jeans finally became (5)________ fashion clothing when famous designers started (6)________ their own styles of jeans, with their own labels on them. Sales of jeans always go up and up because jeans have never been out of fashion.

                   1.A. gets            B. goes             C. arrives         D. comes

                   2.A. go             B. wear            C. call                       D. come

                   3.A. teenagers  B. pupils          C. students       D. youngster

                   4.A. higher       B. costlier        C. longer                    D. cheaper

                   5.A. low           B. high             C. up                        D. old

                   6.A. doing        B. getting         C. making        D. buying

V.Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the questions

FOOTPRINTS ON THE MOON

     Long ago a lot of people thought the moon was a god. Other people thought it was just a light in the sky. And others thought it was a big ball of cheese.

     The telescopes were made. And men saw that the moon was really another world. They wondered what it was like. They dreamed of going there.

     On July 20,1969, that dream came true. Two American men landed on the moon. Their names were Neil Armstrong and Edwin Aldrin. The first thing the men found was that the moon is covered with dust. The dust is so thick that the men left footprints where they walked. Those were the first marks a living thing had ever made on the moon. And they could stay there for years and years. There is no wind or rain to wipe them off.

     The two men walked on the moon for hours. They picked up rocks to bring back to earth for study. They dug up dirt to bring back. They set up machines to find out things people wanted to know. Then they climbed back into their moon landing craft.

     Next day, the landing craft roared as the two men took off from the moon. They joined Michael Collins in the spaceship that waited for them above the moon. Then they were off on their trip back to earth. Behind them they left the plains and tall mountains of the moon. They left the machines they had set up. And they left footprints that may last forever.

1. This story tells ___________

          A. about the first men to walk on the moon.

          B. how men found footprints on the moon.

          C. what the men brought back from their trip to the moon.

          D. about the mountains on the moon

2.  A telescope ___________

          A. makes the moon brighter.

          B. turns the moon into another world.

          C. makes many of men’s dreams come true.

          D. helps people see the moon more clearly.

3.The men brought rocks and dirt from the moon because ___________

          A. they wanted something to show they were there.

          B. people wanted to use them to learn about the moon.

          C. they wanted to keep them as souvenirs.

          D. they might sell them to scientists.

4.When the men returned to earth, they        ___________

          A. left their machines on the moon.    B. destroyed the machines.

          C. carried the machines with them.     D. hid the machines.

5.The next people who go to the moon likely could ___________

          A. find that the machines have disappeared.

          B. leave the first set of footprints on the moon.

          C. find the places where Armstrong and Aldrin walked.

          D. find that dust wiped off the two men’s footprints.

1
16 tháng 6 2021

IV. Choose the word (A, B, C or D) that best fits the blank space in the following passage. (1,5 pt)

     The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many university and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became (4)________. In the 1980s jeans finally became (5)________ fashion clothing when famous designers started (6)________ their own styles of jeans, with their own labels on them. Sales of jeans always go up and up because jeans have never been out of fashion.

                   1.A. gets            B. goes             C. arrives         D. comes

                   2.A. go             B. wear            C. call                       D. come

                   3.A. teenagers  B. pupils          C. students       D. youngster

                   4.A. higher       B. costlier        C. longer                    D. cheaper

                   5.A. low           B. high             C. up                        D. old

                   6.A. doing        B. getting         C. making        D. buying

V.Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the questions

FOOTPRINTS ON THE MOON

     Long ago a lot of people thought the moon was a god. Other people thought it was just a light in the sky. And others thought it was a big ball of cheese.

     The telescopes were made. And men saw that the moon was really another world. They wondered what it was like. They dreamed of going there.

     On July 20,1969, that dream came true. Two American men landed on the moon. Their names were Neil Armstrong and Edwin Aldrin. The first thing the men found was that the moon is covered with dust. The dust is so thick that the men left footprints where they walked. Those were the first marks a living thing had ever made on the moon. And they could stay there for years and years. There is no wind or rain to wipe them off.

     The two men walked on the moon for hours. They picked up rocks to bring back to earth for study. They dug up dirt to bring back. They set up machines to find out things people wanted to know. Then they climbed back into their moon landing craft.

     Next day, the landing craft roared as the two men took off from the moon. They joined Michael Collins in the spaceship that waited for them above the moon. Then they were off on their trip back to earth. Behind them they left the plains and tall mountains of the moon. They left the machines they had set up. And they left footprints that may last forever.

1. This story tells ___________

          A. about the first men to walk on the moon.

          B. how men found footprints on the moon.

          C. what the men brought back from their trip to the moon.

          D. about the mountains on the moon

2.  A telescope ___________

          A. makes the moon brighter.

          B. turns the moon into another world.

          C. makes many of men’s dreams come true.

          D. helps people see the moon more clearly.

3.The men brought rocks and dirt from the moon because ___________

          A. they wanted something to show they were there.

          B. people wanted to use them to learn about the moon.

          C. they wanted to keep them as souvenirs.

          D. they might sell them to scientists.

4.When the men returned to earth, they        ___________

          A. left their machines on the moon.    B. destroyed the machines.

          C. carried the machines with them.     D. hid the machines.

5.The next people who go to the moon likely could ___________

          A. find that the machines have disappeared.

          B. leave the first set of footprints on the moon.

          C. find the places where Armstrong and Aldrin walked.

          D. find that dust wiped off the two men’s footprints.

I. Choose the word (A, B, C or D) that best fits the blank space in the following passage.      The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many universities and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became...
Đọc tiếp

undefined

I. Choose the word (A, B, C or D) that best fits the blank space in the following passage.

      The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many universities and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became (4)________. In the 1980s jeans finally became (5)________ fashion clothing when famous designers started (6)________ their own styles of jeans, with their own labels on them. Sales of jeans always go up and up because jeans have never been out of fashion.

Question 1.   A. gets         B. goes          C. arrives              D. comes

Question 2.   A. go            B. wear          C. call                   D. come

Question 3.   A. teenagers B. pupils       C. students           D. youngster

Question 4.   A. higher      B. costlier      C. longer               D. cheaper

Question 5.   A. low           B. high           C. up                    D. old

Question 6.   A. doing       B. getting       C. making             D. buying

II. Use the correct form of the word given in each sentence. 

Question 7. We are worried that rivers and canals are becoming more and more ___________. (pollute)

Question 8. TV ____________ are advertisements in which goods and services are promoted. (commerce)

Question 9. It is __________that some people poach fish in the Nhieu Loc Canal. (disappoint)

Question 10. Christmas is ____________ celebrated in many countries. (joy)

Question 11. Here is tomorrow’s weather ____________. Ho Chi Minh City will be sunny, and ... (cast)

Question 12. My sister is wearing a T-shirt of the latest model. She always dresses ____________. (fashion)

III. Use the correct tense or form of the verb given in each sentence. 

Question 13. Unless she ____________ the flowers regularly, they will wither. (water)

Question 14. We all expect that Anh Vien ____________ the most outstanding athlete in this SEA GAMES. (become)

Question 15. He ____________ five comic books since last Monday. (read)

Question 16. The teacher suggested ____________ these units carefully. (revise)

Good luck các em!

6
13 tháng 4 2021

I. Choose the word (A, B, C or D) that best fits the blank space in the following passage.

      The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many universities and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became (4)________. In the 1980s jeans finally became (5)________ fashion clothing when famous designers started (6)________ their own styles of jeans, with their own labels on them. Sales of jeans always go up and up because jeans have never been out of fashion.

Question 1.   A. gets         B. goes          C. arrives              D. comes

Question 2.   A. go            B. wear          C. call                   D. come

Question 3.   A. teenagers B. pupils       C. students           D. youngster

Question 4.   A. higher      B. costlier      C. longer               D. cheaper

Question 5.   A. low           B. high           C. up                    D. old

Question 6.   A. doing       B. getting       C. making             D. buying

II. Use the correct form of the word given in each sentence. 

Question 7. We are worried that rivers and canals are becoming more and more ______polluted_____. (pollute)

Question 8. TV ______commercials______ are advertisements in which goods and services are promoted. (commerce)

Question 9. It is _____disappointing_____that some people poach fish in the Nhieu Loc Canal. (disappoint)

Question 10. Christmas is ______joyfully______ celebrated in many countries. (joy)

Question 11. Here is tomorrow’s weather ________forecast____. Ho Chi Minh City will be sunny, and ... (cast)

Question 12. My sister is wearing a T-shirt of the latest model. She always dresses _______fashionable_____. (fashion)

III. Use the correct tense or form of the verb given in each sentence. 

Question 13. Unless she ______waters______ the flowers regularly, they will wither. (water)

Question 14. We all expect that Anh Vien ______will become______ the most outstanding athlete in this SEA GAMES. (become)

Question 15. He _____has read_______ five comic books since last Monday. (read)

Question 16. The teacher suggested ____revising________ these units carefully. (revise)

I. Choose the word (A, B, C or D) that best fits the blank space in the following passage.

      The word jeans (1)________ from a kind of material that was made in Europe. It is a strong material and it does not (2)________ out easily. In the 1960s, many universities and college (3)________ wore jeans. Designers made different styles of jeans to match the 1960s’ fashions; embroidered jeans, painted jeans and so on. In the 1970s more and more people started wearing jeans because they became (4)________. In the 1980s jeans finally became (5)________ fashion clothing when famous designers started (6)________ their own styles of jeans, with their own labels on them. Sales of jeans always go up and up because jeans have never been out of fashion.

Question 1.   A. gets         B. goes          C. arrives              D. comes

Question 2.   A. go            B. wear          C. call                   D. come

Question 3.   A. teenagers B. pupils       C. students           D. youngster

Question 4.   A. higher      B. costlier      C. longer               D. cheaper

Question 5.   A. low           B. high           C. up                    D. old

Question 6.   A. doing       B. getting       C. making             D. buying

II. Use the correct form of the word given in each sentence. 

Question 7. We are worried that rivers and canals are becoming more and more ______polluted_____. (pollute)

Question 8. TV ______commercials______ are advertisements in which goods and services are promoted. (commerce)

Question 9. It is _____disappointing_____that some people poach fish in the Nhieu Loc Canal. (disappoint)

Question 10. Christmas is ______joyfully______ celebrated in many countries. (joy)

Question 11. Here is tomorrow’s weather ________forecast____. Ho Chi Minh City will be sunny, and ... (cast)

Question 12. My sister is wearing a T-shirt of the latest model. She always dresses _______fashionable_____. (fashion)

III. Use the correct tense or form of the verb given in each sentence. 

Question 13. Unless she ______waters______ the flowers regularly, they will wither. (water)

Question 14. We all expect that Anh Vien ______will become______ the most outstanding athlete in this SEA GAMES. (become)

Question 15. He _____has read_______ five comic books since last Monday. (read)

Question 16. The teacher suggested ____revising________ these units carefully. (revise)

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                                The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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...
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                               

The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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 are 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. Freshwater Aquarium Fish

Playlist Freshwater Aquarium Fish

       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 or 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 Teacher. OUP

Which of the following could best serve as the title of the passage?

A. Electrical Energy

B. Electrical Devices

C. Electrical Insulators

D. Electrical Conductivity

1
28 tháng 5 2018

Đáp án : D

Cả bài nói về khả năng dẫn điện, từ đặc tính dẫn điện của kim loại, các chất dẫn điện kém như nước, tới các chất cách điện

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                                The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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...
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                               

The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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 are 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. Freshwater Aquarium Fish

Playlist Freshwater Aquarium Fish

       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 or 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 Teacher. OUP

Electrical conductivity is                    

A. one of the most important properties of metals 

B. one of the key properties of most solid materials 

C. impossible for any substance when it is dissolved in water 

D. completely impossible for silicon

1
9 tháng 8 2018

Đáp án : A

Ngay dòng đầu tiên: The ability to conduct electricity is one of the key properties of a metal

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 35 to 42.Today we take electricity for granted and perhaps we do not realize just how useful this discovery has been. Steam was the first invention that replaced wind power. It was used to drive engines and was passed through pipes and radiators to warm rooms. Petrol mixed with air was the next invention that provided power. Exploded in a cylinder, it...
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 questions from 35 to 42.

Today we take electricity for granted and perhaps we do not realize just how useful this discovery has been. Steam was the first invention that replaced wind power. It was used to drive engines and was passed through pipes and radiators to warm rooms. Petrol mixed with air was the next invention that provided power. Exploded in a cylinder, it drove a motor engine. Beyond these simple and direct uses, those forms have not much adaptability.

On the other hand, we make use of electricity in thousands of ways. From the powerful voltages that drive our electric trains to the tiny current needed to work a simple calculator, and from the huge electric magnet in steel works that can lift 10 tons to the tiny electric magnet in a doorbell, all are powered by electricity. An electric current can be made with equal ease to heat a huge mass of molten metal in a furnace, or to boil a jug for a cup of coffee.

Other than atomic energy, which has not as yet been harnessed to the full, electricity is the greatest power in the world. It is flexible, and so adaptable for any task for which it is wanted. It travels so easily and with incredible speed along wires or conductors that it can be supplied instantly over vast distances.

To generate electricity, huge turbines or generators must be turned. In Australia they use coal or water to drive this machinery. When dams are built, falling water is used to drive the turbines without polluting the atmosphere with smoke from coal.

Atomic power is used in several countries but there is always the fear of an accident. A tragedy once occurred at Chernobyl, in Ukraine, at an atomic power plant used to make electricity. The reactor leaked, which caused many deaths through radiation.

Now scientists are examining new ways of creating electricity without harmful effects to the environment. They may harness the tides as they flow in and out of bays. Most importantly, they hope to trap sunlight more efficiently. We do use solar heaters for swimming pools but as yet improvement in the capacity of the solar cells to create more current is necessary. When this happens, electric cars will be viable and the world will rid itself of the toxic gases given off by trucks and cars that burn fossil fuels

Before electricity, what was sometimes passed through pipes to heat rooms? 

A. Gas 

B. Petrol 

C. Steam 

D. Hot wind 

1
28 tháng 2 2017

Chọn C

Kiến thức: Đọc hiểu

Giải thích:

Trước khi có điện, cái gì đôi khi đi qua các đường ống để sưởi ấm phòng?

  A. Khí ga                 

B. Xăng dầu               

C. Hơi nước                

D. Gió nóng

Thông tin: Steam was the first invention that replaced wind power. It was used to drive engines and was passed through pipes and radiators to warm rooms.

Tạm dịch: Hơi nước là phát minh đầu tiên dùng thay thế cho năng lượng gió. Nó được sử dụng để điều khiển động cơ và được dẫn qua các đường ống và lò sưởi để sưởi ấm các căn phòng

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...
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 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

Salt in its solid state is not able to conduct electricity because ______.

A. . its charged ions can flow easily

B. it cannot create any charged ions

C. it has free electrons

D. its charged ions are not free to move

1
5 tháng 2 2017

Đáp án D

Muối ở thể rắn không thể dẫn điện bởi vì

A.các ion mang điện của nó có thể chảy dễ dàng

B. nó không thể tạo ra ion mang điện

C. nó có các electron tự do

D. các ion mang điện của nó không tự do di chuyển

Dẫn chứng: In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow

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                                The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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...
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                               

The ability to conduct electricity is one of the key properties of  a metal. Other solid material 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 are 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. Freshwater Aquarium Fish

Playlist Freshwater Aquarium Fish

       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 or 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 Teacher. OUP

We can have problems when touching electrical devices with wet hands because               .

A. the eater itself is a good conductor of electricity 

B. the water dissolves the salt on our skin and becomes more conductive 

C. the water contains too many neutral molecules 

D. the water containing no charged particles makes it more conductive

1
21 tháng 6 2017

Đáp án : B

Câu cuối: 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 -> muối từ mồ hôi trên da chúng ta hòa tan trong nước khiến nước dẫn điện hơn