单选题
What aspect of crystals does the class mainly discuss?
【正确答案】
B
【答案解析】[听力原文]
M1: Crystals are solid minerals in which the atoms are arranged in a regular pattern. Heat, pressure, weather, and time affect the way minerals form, and each type of mineral has a specific chemical composition. They also have a typical, regular shape—no matter where they"re found. Most minerals have a crystalline structure, with smooth, flat faces, regular angles, and sharp edges. Crystals grow when geologic activity deposits minerals in cavities or fissures underground. The minerals" atoms combine and arrange themselves in a regular pattern. Different combinations of elements make different types of minerals. However, specific combinations always behave in the same way. The internal atomic structure of crystals determines their regular shape and other properties. Each atom of a crystal has its own special position and is tied to other atoms by bonding forces. The atoms of a particular mineral always group in the same way to form crystals of that mineral. On the basis of its chemistry, a crystal falls into one of 32 classes. Mineralogists classify crystals by measuring the angles of all of the faces of the crystal. I hope you"ve all had a chance to read Chapter Eight. That chapter covers the different properties of crystals, such as color, hardness, cleavage, and what we call habit. Who can tell us how a crystal gets its color? Tina, would you like to?
W: Sure. A crystal looks a particular color because of your eye and your brain reacting to different wavelengths of light. For example, when, uh, when white light—daylight—falls on a crystal, some of the wavelengths are reflected, and some are absorbed. If some are absorbed, the others will make up a color other than white because some of the wavelengths that make up the white light are missing. Some minerals are always the same color. That"s because certain light-absorbing atoms are a basic part of their crystal structure.
M1: Well done, Tina. Now, who"d care to tackle habit? William?
M2: The habit is the general shape of a crystal, like a cube or a hexagon. The habit of a crystal is symmetrical—like a mirror image—the same shape on both sides of an imaginary line that passes through its center. Habit is sometimes a way to identify a crystal. For example, salt crystals have the shape of a cube. But crystals of the same mineral don"t always look alike. There"s one mineral—pyrite—that can form a cube or an octahedron.
M1: Good job, William. And remember, it"s the arrangement of the atoms in the mineral that determine its outward appearance. There"s another characteristic I"d like to mention, and that"s cleavage, or how a crystal breaks. Some crystals split along well-defined planes called cleavage planes. Cleavage usually occurs along the weakest plane in the structure. The cleavage of a crystal is direct evidence of the orderly arrangement of the atoms. In order to identify a crystal, we have to test its properties. We can study properties like color, habit, and cleavage by using a hand lens. Now, I"d like you all to come up and take a look at some of the crystals I brought to class. There are some hand lenses, too. See what you can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight.
What aspect of crystals does the class mainly discuss?
The class mainly discusses the properties of crystals. The professor says Crystals are solid minerals in which the atoms are arranged in a regular pattern; Most minerals have a crystalline structure, with smooth, flat faces, regular angles, and sharp edges; That chapter covers the different properties of crystals, such as color, hardness, cleavage, and what we call habit.
M1: Crystals are solid minerals in which the atoms are arranged in a regular pattern. Heat, pressure, weather, and time affect the way minerals form, and each type of mineral has a specific chemical composition. They also have a typical, regular shape—no matter where they"re found. Most minerals have a crystalline structure, with smooth, flat faces, regular angles, and sharp edges. Crystals grow when geologic activity deposits minerals in cavities or fissures underground. The minerals" atoms combine and arrange themselves in a regular pattern. Different combinations of elements make different types of minerals. However, specific combinations always behave in the same way. The internal atomic structure of crystals determines their regular shape and other properties. Each atom of a crystal has its own special position and is tied to other atoms by bonding forces. The atoms of a particular mineral always group in the same way to form crystals of that mineral. On the basis of its chemistry, a crystal falls into one of 32 classes. Mineralogists classify crystals by measuring the angles of all of the faces of the crystal. I hope you"ve all had a chance to read Chapter Eight. That chapter covers the different properties of crystals, such as color, hardness, cleavage, and what we call habit. Who can tell us how a crystal gets its color? Tina, would you like to?
W: Sure. A crystal looks a particular color because of your eye and your brain reacting to different wavelengths of light. For example, when, uh, when white light—daylight—falls on a crystal, some of the wavelengths are reflected, and some are absorbed. If some are absorbed, the others will make up a color other than white because some of the wavelengths that make up the white light are missing. Some minerals are always the same color. That"s because certain light-absorbing atoms are a basic part of their crystal structure.
M1: Well done, Tina. Now, who"d care to tackle habit? William?
M2: The habit is the general shape of a crystal, like a cube or a hexagon. The habit of a crystal is symmetrical—like a mirror image—the same shape on both sides of an imaginary line that passes through its center. Habit is sometimes a way to identify a crystal. For example, salt crystals have the shape of a cube. But crystals of the same mineral don"t always look alike. There"s one mineral—pyrite—that can form a cube or an octahedron.
M1: Good job, William. And remember, it"s the arrangement of the atoms in the mineral that determine its outward appearance. There"s another characteristic I"d like to mention, and that"s cleavage, or how a crystal breaks. Some crystals split along well-defined planes called cleavage planes. Cleavage usually occurs along the weakest plane in the structure. The cleavage of a crystal is direct evidence of the orderly arrangement of the atoms. In order to identify a crystal, we have to test its properties. We can study properties like color, habit, and cleavage by using a hand lens. Now, I"d like you all to come up and take a look at some of the crystals I brought to class. There are some hand lenses, too. See what you can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight.
What aspect of crystals does the class mainly discuss?
The class mainly discusses the properties of crystals. The professor says Crystals are solid minerals in which the atoms are arranged in a regular pattern; Most minerals have a crystalline structure, with smooth, flat faces, regular angles, and sharp edges; That chapter covers the different properties of crystals, such as color, hardness, cleavage, and what we call habit.
单选题
What factor primarily gives a crystal its regular shape?
【正确答案】
A
【答案解析】[听力原文]
What factor primarily gives a crystal its regular shape?
The professor says The minerals" atoms combine and arrange themselves in a regular pattern; The internal atomic structure of crystals determines their regular shape and other properties.
What factor primarily gives a crystal its regular shape?
The professor says The minerals" atoms combine and arrange themselves in a regular pattern; The internal atomic structure of crystals determines their regular shape and other properties.
单选题
Why does the professor say this:
【正确答案】
C
【答案解析】[听力原文]
Why does the professor say this:
"I hope you"ve all had a chance to read Chapter Eight."
The professor"s purpose is to introduce the topics that the class will discuss next. Chapter Eight describes different properties of crystals, which are the focus of the discussion.
Why does the professor say this:
"I hope you"ve all had a chance to read Chapter Eight."
The professor"s purpose is to introduce the topics that the class will discuss next. Chapter Eight describes different properties of crystals, which are the focus of the discussion.
单选题
According to the discussion, why do some minerals have a particular color?
【正确答案】
B
【答案解析】[听力原文]
According to the discussion, why do some minerals have a particular color?
The student says A crystal looks a particular color because of your eye and your brain reacting to different wavelengths of light; Some minerals are always the same color. That"s because certain light-absorbing atoms are a basic part of their crystal structure.
According to the discussion, why do some minerals have a particular color?
The student says A crystal looks a particular color because of your eye and your brain reacting to different wavelengths of light; Some minerals are always the same color. That"s because certain light-absorbing atoms are a basic part of their crystal structure.
多选题
Which of the following sentences describe a crystal"s property of habit?
Click on 2 answers.
Click on 2 answers.
【正确答案】
A、D
【答案解析】[听力原文]
Which of the following sentences describe a crystal"s property of habit?
A crystal"s general shape might be a cube or a hexagon: The habit is the general shape of a crystal, like a cube or a hexagon. The same shape is on both sides of an invisible line through the center: The habit of a crystal is symmetrical—like a mirror image—the same shape on both sides of an imaginary line that passes through its center.
Which of the following sentences describe a crystal"s property of habit?
A crystal"s general shape might be a cube or a hexagon: The habit is the general shape of a crystal, like a cube or a hexagon. The same shape is on both sides of an invisible line through the center: The habit of a crystal is symmetrical—like a mirror image—the same shape on both sides of an imaginary line that passes through its center.
单选题
Why does the professor say this:
【正确答案】
D
【答案解析】[听力原文]
Why does the professor say this:
"There are some hand lenses, too. See what you can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight."
The professor"s purpose is to direct the students in identifying some crystals. He wants the students to use the hand lenses to examine the crystals that he brought to class. He directs the students to see what they can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight.
Why does the professor say this:
"There are some hand lenses, too. See what you can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight."
The professor"s purpose is to direct the students in identifying some crystals. He wants the students to use the hand lenses to examine the crystals that he brought to class. He directs the students to see what they can figure out by comparing these specimens with the chart of crystals at the end of Chapter Eight.