单选题
单选题
What does the professor mainly discuss?
【正确答案】
B
【答案解析】[听力原文]
W1: I"m glad to see everyone made it to school safely this morning. I wish I could say the same for myself, but I had a rather close call when I was getting on the expressway. I was on the on-ramp, and my car suddenly skidded and turned completely around, so I ended up with my car facing backward. Luckily, there was no one right behind me. I was able to turn my car around and slowly drive on. You see, what had happened was, I ran into a patch of black ice. And the nature of black ice is that you just don"t see it coming because it"s practically invisible. Generally, the formation of ice requires two conditions: the presence of water and temperatures below freezing. However, black ice can form on the highway when the air temperature is slightly above freezing but the ground temperature is below freezing. That"s how it was at seven o"clock this morning when I was driving to campus. The air temperature was 34 degrees Fahrenheit; however, the overnight low had been in the low twenties, so the ground temperature was below freezing. The black ice formed when evaporation on the wet surface of the pavement—it was mist, actually, water vapor—when the mist was exposed to above-freezing air temperatures. The evaporation lowered the surface temperature to below freezing, and this then froze the very thin layer of mist on the surface of the pavement.
M: Excuse me, Dr. West. I"m not sure I heard you correctly. Are you saying it"s possible for ice to form, even when it"s not freezing outside?
W1: Yes, and black ice is a good example of this. The air temperature can be above freezing, but the temperature of a wet surface like pavement can be lower. The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees. Water evaporates from the wet clothes, which are colder than the air, and the vapor rising from the laundry freezes. So your clothes are then covered with a thin film of ice. One of the reasons black ice takes us so much by surprise is that we don"t expect to find ice when the thermometer says it"s above freezing—the air temperature, that is. But air temperature can be deceiving, and we have to be careful, especially on mornings like today. We usually think of ice formation as the freezing of liquid water, but ice can also form by the process of sublimation. Sublimation is when water changes state from a gas directly to a solid—or from a solid to a gas—without first becoming a liquid. Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas.
M: So, what you"re saying is, black ice is formed by sublimation?
W1: Yes. Black ice is formed by sublimation, directly from water vapor on the surface of the road. Black ice is a form of frost. Some other forms of frost are ground frost and the frost you see on windows on cold winter nights. It can look like delicate feathery patterns of crystals on your windowpane, or it can be fernlike crystals several centimeters long on the twigs and branches of trees.
W2: Dr. West...um...could you explain why the frost on a window looks so pretty? I mean, why does the frost make such beautiful patterns?
W1: Water vapor forms as frost on the surface of an object if the temperature of the surface falls below both the freezing point and the point at which water vapor condenses to a liquid. In the case of window frost, the temperature of the window glass has to be below freezing. The window is chilled because it"s losing heat to the colder air outside. By the way, the beautiful patterns of window frost are due to its slightly curved crystals, because of organic impurities on the glass—dust and dirt—that interfere with crystal growth.
What does the professor mainly discuss?
The professor mainly discusses the formation of ice from water vapor, specifically the formation of black ice. The professor says...black ice can form on the highway...; The black ice formed when evaporation on the wet surface of the pavement—it was mist, actually, water vapor—when the mist was exposed to above-freezing air temperatures; ...this then froze the very thin layer of mist on the surface of the pavement.
W1: I"m glad to see everyone made it to school safely this morning. I wish I could say the same for myself, but I had a rather close call when I was getting on the expressway. I was on the on-ramp, and my car suddenly skidded and turned completely around, so I ended up with my car facing backward. Luckily, there was no one right behind me. I was able to turn my car around and slowly drive on. You see, what had happened was, I ran into a patch of black ice. And the nature of black ice is that you just don"t see it coming because it"s practically invisible. Generally, the formation of ice requires two conditions: the presence of water and temperatures below freezing. However, black ice can form on the highway when the air temperature is slightly above freezing but the ground temperature is below freezing. That"s how it was at seven o"clock this morning when I was driving to campus. The air temperature was 34 degrees Fahrenheit; however, the overnight low had been in the low twenties, so the ground temperature was below freezing. The black ice formed when evaporation on the wet surface of the pavement—it was mist, actually, water vapor—when the mist was exposed to above-freezing air temperatures. The evaporation lowered the surface temperature to below freezing, and this then froze the very thin layer of mist on the surface of the pavement.
M: Excuse me, Dr. West. I"m not sure I heard you correctly. Are you saying it"s possible for ice to form, even when it"s not freezing outside?
W1: Yes, and black ice is a good example of this. The air temperature can be above freezing, but the temperature of a wet surface like pavement can be lower. The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees. Water evaporates from the wet clothes, which are colder than the air, and the vapor rising from the laundry freezes. So your clothes are then covered with a thin film of ice. One of the reasons black ice takes us so much by surprise is that we don"t expect to find ice when the thermometer says it"s above freezing—the air temperature, that is. But air temperature can be deceiving, and we have to be careful, especially on mornings like today. We usually think of ice formation as the freezing of liquid water, but ice can also form by the process of sublimation. Sublimation is when water changes state from a gas directly to a solid—or from a solid to a gas—without first becoming a liquid. Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas.
M: So, what you"re saying is, black ice is formed by sublimation?
W1: Yes. Black ice is formed by sublimation, directly from water vapor on the surface of the road. Black ice is a form of frost. Some other forms of frost are ground frost and the frost you see on windows on cold winter nights. It can look like delicate feathery patterns of crystals on your windowpane, or it can be fernlike crystals several centimeters long on the twigs and branches of trees.
W2: Dr. West...um...could you explain why the frost on a window looks so pretty? I mean, why does the frost make such beautiful patterns?
W1: Water vapor forms as frost on the surface of an object if the temperature of the surface falls below both the freezing point and the point at which water vapor condenses to a liquid. In the case of window frost, the temperature of the window glass has to be below freezing. The window is chilled because it"s losing heat to the colder air outside. By the way, the beautiful patterns of window frost are due to its slightly curved crystals, because of organic impurities on the glass—dust and dirt—that interfere with crystal growth.
What does the professor mainly discuss?
The professor mainly discusses the formation of ice from water vapor, specifically the formation of black ice. The professor says...black ice can form on the highway...; The black ice formed when evaporation on the wet surface of the pavement—it was mist, actually, water vapor—when the mist was exposed to above-freezing air temperatures; ...this then froze the very thin layer of mist on the surface of the pavement.
单选题
Why does the professor talk about her drive to school that morning?
【正确答案】
D
【答案解析】[听力原文]
Why does the professor talk about her drive to school that morning?
The professor"s purpose is to lead into the topic of discussion, black ice and how it forms. The professor says...I had a rather close call when I was getting on the expressway; ...I ran into a patch of black ice.
Why does the professor talk about her drive to school that morning?
The professor"s purpose is to lead into the topic of discussion, black ice and how it forms. The professor says...I had a rather close call when I was getting on the expressway; ...I ran into a patch of black ice.
单选题
Listen again to part of the discussion. Then answer the question.
Why does the professor say this:
Why does the professor say this:
【正确答案】
C
【答案解析】[听力原文]
Listen again to part of the discussion. Then answer the question.
"Excuse me, Dr. West. I"m not sure I heard you correctly.
Are you saying it"s possible for ice to form, even when it"s not freezing outside?"
"Yes, and black ice is a good example of this. The air temperature can be above freezing, but the temperature of a wet surface like pavement can be lower. The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees."
Why does the professor say this:
"The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees."
The professor"s purpose is to illustrate a process in another way. The process is the formation of ice from water vapor even when it is not freezing outside. Black ice is one example; the freezing of wet laundry is another example.
Listen again to part of the discussion. Then answer the question.
"Excuse me, Dr. West. I"m not sure I heard you correctly.
Are you saying it"s possible for ice to form, even when it"s not freezing outside?"
"Yes, and black ice is a good example of this. The air temperature can be above freezing, but the temperature of a wet surface like pavement can be lower. The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees."
Why does the professor say this:
"The same thing happens when wet laundry is left hanging outside and it freezes solid at an air temperature of 35 degrees."
The professor"s purpose is to illustrate a process in another way. The process is the formation of ice from water vapor even when it is not freezing outside. Black ice is one example; the freezing of wet laundry is another example.
单选题
How does the professor explain sublimation?
【正确答案】
A
【答案解析】[听力原文]
How does the professor explain sublimation?
The professor provides examples and a definition of sublimation. Examples: black ice, freezing laundry, and frost on a windowpane. Definition: Sublimation is when water changes state from a gas directly to a solid—or from a solid to a gas—without first becoming a liquid. Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas.
How does the professor explain sublimation?
The professor provides examples and a definition of sublimation. Examples: black ice, freezing laundry, and frost on a windowpane. Definition: Sublimation is when water changes state from a gas directly to a solid—or from a solid to a gas—without first becoming a liquid. Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas.
单选题
Which of the following is an example of sublimation?
【正确答案】
C
【答案解析】[听力原文]
Which of the following is an example of sublimation?
The professor says Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas; Black ice is formed by sublimation, directly from water vapor on the surface of the road.
Which of the following is an example of sublimation?
The professor says Ice formed in this way—by sublimation—forms directly from water vapor, or mist, which is a gas; Black ice is formed by sublimation, directly from water vapor on the surface of the road.
多选题
What conditions cause frost to form in beautiful patterns on window glass?
Click on 2 answers.
Click on 2 answers.
【正确答案】
B、C
【答案解析】[听力原文]
What conditions cause frost to form in beautiful patterns on window glass?
Frost forms in beautiful patterns on window glass when the temperature of the glass is below freezing:/t can look like delicate feathery patterns of crystals on your windowpane; ...the temperature of the window glass has to be below freezing. Another condition is dirt on the glass, which affects the growth of ice crystals: ...the beautiful patterns of window frost are due to its slightly curved crystals, because of organic impurities on the glass—dust and dirt—that interfere with crystal growth.
What conditions cause frost to form in beautiful patterns on window glass?
Frost forms in beautiful patterns on window glass when the temperature of the glass is below freezing:/t can look like delicate feathery patterns of crystals on your windowpane; ...the temperature of the window glass has to be below freezing. Another condition is dirt on the glass, which affects the growth of ice crystals: ...the beautiful patterns of window frost are due to its slightly curved crystals, because of organic impurities on the glass—dust and dirt—that interfere with crystal growth.