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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 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?

Xem chi tiết 662 lượt xem 6 năm trước

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

Xem chi tiết 821 lượt xem 6 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.Most traditional human life in deserts is nomadic. It (35) ________ in hot deserts on finding water, and on following infrequent rains to (36) ________ grazing for livestock. In cold deserts, it depends on finding good hunting and fishing grounds, on sheltering from blizzards and winter (37) ________, and on storing enough food for winter. Permanent settlement in both kinds of deserts requires permanent water, food sources and adequate shelter, or the technology and energy sources to (38) ________ it.Many deserts are flat and featureless, lacking landmarks, or composed of repeating landforms such as sand (39) ________ or the jumbled ice-fields of glaciers. Advanced skills or devices are required to navigate through such landscapes and (40) ________ travelers may die when supplies run (41) ________ after becoming lost. In addition, sandstorms or blizzards may cause disorientation in severely-reduced visibility.The (42) ________ represented by wild animals in deserts has featured in explorers' accounts but does not cause higher (43) ________ of death than in other environments such as rainforests or savanna woodland, and generally does not affect human distribution. Defense against polar bears may be advisable in some areas of the Arctic. Precautions against snakes and scorpions in choosing (44) ________ at which to camp in some hot deserts should be taken.Điền câu 37

Xem chi tiết 307 lượt xem 6 năm trước

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 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  Water is a poor conductor because it contains ______.

Xem chi tiết 716 lượt xem 6 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.Most traditional human life in deserts is nomadic. It (35) ________ in hot deserts on finding water, and on following infrequent rains to (36) ________ grazing for livestock. In cold deserts, it depends on finding good hunting and fishing grounds, on sheltering from blizzards and winter (37) ________, and on storing enough food for winter. Permanent settlement in both kinds of deserts requires permanent water, food sources and adequate shelter, or the technology and energy sources to (38) ________ it.Many deserts are flat and featureless, lacking landmarks, or composed of repeating landforms such as sand (39) ________ or the jumbled ice-fields of glaciers. Advanced skills or devices are required to navigate through such landscapes and (40) ________ travelers may die when supplies run (41) ________ after becoming lost. In addition, sandstorms or blizzards may cause disorientation in severely-reduced visibility.The (42) ________ represented by wild animals in deserts has featured in explorers' accounts but does not cause higher (43) ________ of death than in other environments such as rainforests or savanna woodland, and generally does not affect human distribution. Defense against polar bears may be advisable in some areas of the Arctic. Precautions against snakes and scorpions in choosing (44) ________ at which to camp in some hot deserts should be taken.Điền câu 36

Xem chi tiết 418 lượt xem 6 năm trước

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

Xem chi tiết 1.3 K lượt xem 6 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.Most traditional human life in deserts is nomadic. It (35) ________ in hot deserts on finding water, and on following infrequent rains to (36) ________ grazing for livestock. In cold deserts, it depends on finding good hunting and fishing grounds, on sheltering from blizzards and winter (37) ________, and on storing enough food for winter. Permanent settlement in both kinds of deserts requires permanent water, food sources and adequate shelter, or the technology and energy sources to (38) ________ it.Many deserts are flat and featureless, lacking landmarks, or composed of repeating landforms such as sand (39) ________ or the jumbled ice-fields of glaciers. Advanced skills or devices are required to navigate through such landscapes and (40) ________ travelers may die when supplies run (41) ________ after becoming lost. In addition, sandstorms or blizzards may cause disorientation in severely-reduced visibility.The (42) ________ represented by wild animals in deserts has featured in explorers' accounts but does not cause higher (43) ________ of death than in other environments such as rainforests or savanna woodland, and generally does not affect human distribution. Defense against polar bears may be advisable in some areas of the Arctic. Precautions against snakes and scorpions in choosing (44) ________ at which to camp in some hot deserts should be taken.Điền câu 35

Xem chi tiết 304 lượt xem 6 năm trước

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 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. OUPThe word “outermost” in paragraph 1 mostly means ______.

Xem chi tiết 773 lượt xem 6 năm trước

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

Xem chi tiết 1.3 K lượt xem 6 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that bestfits each of the numbered blanks from 31 to35.In addition to the challenge to be excellent, American schools have been facing novel problems. They must (31)______ with an influx of immigrant children, many of whom speak little or no English. They must respond to demands that the curriculum reflect the various cultures of all children. Schools must make sure that students develop basic skills for the job market, and they must consider the needs of nontraditional students, such as teenage mothers.Schools are (32)______ these problems in ways that reflect the diversity of the US educational system. They are hiring or training large numbers of teachers of English as a second language and, in some communities, setting up bilingual schools. They are opening up the traditional European-centered curriculum to embrace material from African, Asian, and other cultures. Schools are also teaching cognitive skills to the (33)______ 40 percent of American students who do not go on to higher education. In the (34)______ of a recent report by the Commission on Achieving Necessary Skills, “A strong back, the willingness to work, and a high school diploma were once all that was necessary to (35)______ a start in America. They are no longer. A well- developed mind, a continued willingness to learn and the ability to put knowledge to work are the new keys to the future of our young people, the success of our business, and the economic well-being of the nation.”Điền ô 35

Xem chi tiết 611 lượt xem 6 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that bestfits each of the numbered blanks from 31 to35.In addition to the challenge to be excellent, American schools have been facing novel problems. They must (31)______ with an influx of immigrant children, many of whom speak little or no English. They must respond to demands that the curriculum reflect the various cultures of all children. Schools must make sure that students develop basic skills for the job market, and they must consider the needs of nontraditional students, such as teenage mothers.Schools are (32)______ these problems in ways that reflect the diversity of the US educational system. They are hiring or training large numbers of teachers of English as a second language and, in some communities, setting up bilingual schools. They are opening up the traditional European-centered curriculum to embrace material from African, Asian, and other cultures. Schools are also teaching cognitive skills to the (33)______ 40 percent of American students who do not go on to higher education. In the (34)______ of a recent report by the Commission on Achieving Necessary Skills, “A strong back, the willingness to work, and a high school diploma were once all that was necessary to (35)______ a start in America. They are no longer. A well- developed mind, a continued willingness to learn and the ability to put knowledge to work are the new keys to the future of our young people, the success of our business, and the economic well-being of the nation.”Điền ô 34

Xem chi tiết 293 lượt xem 6 năm trước