K
Khách

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

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

The atoms of a metal can bond together because                    

A. the lost electrons cannot move freely in the sea of electrons 

B. electrons can flow in a single direction 

C. they lose all of electrons 

D. negatively charged electrons attract positive ions

1
31 tháng 10 2018

Đáp án : D

Từ dòng 4: 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. ... Since the electrons are negatively charged they attract the ions and this is what keeps the structure together. -> để gắn kết với nhau, các nguyên tử kim loại mất ít nhất một trong những electron ngoài cùng,  khiến cho nguyên tử mang điện tích dương, trở thành các ion thực sự… vì các electron mang điện tích âm, chúng hút những ion và điều này tạo nên cấu trúc bền vững -----> các nguyên tử gắn kết vì các electron mang điện tích âm hút ion dương

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

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

A. the absence of free electrons

B. its atoms with a positive charge 

C. the way its atoms bond together 

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

1
19 tháng 8 2017

Đáp án : C

Từ cuối dòng 3: The ability of metals to conduct electricity is due to how their atoms bond together (= bởi cách các phân tử gắn kết với nhau)

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

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

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 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

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

The word “outermost” in paragraph 1 mostly means                    

A. the lightest

B. nearest to the inside

C. furthest from the inside

D. the heaviest

1
10 tháng 6 2019

Đáp án : C

Outermost = ngoài cùng. furthest from the inside = ở xa nhất so với bên trong

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

The word “they” in paragraph 3 refers to                   

A. charged ions

B. electric currents 

C. charged particles

 D.  electrical insulator

1
18 tháng 4 2018

Đáp án : D

Xét cả câu: 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 = các chất cách điện là các chất không thể dẫn điện tốt, bởi vì chúng không chứa các hạt mang điện hay các hạt mang điện mà chúng có thể chứa không di chuyển dễ dàng -à chúng chính là “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

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