10 Average molecular weight

A.Many physical properties

B.Polymerization reactions

C.No

D.No

A、Many physical properties

B、Polymerization reactions

C、No

D、No

A、It is valid for ideal gas systems in equilibrium state.

B、For the same gas system, the distribution changes if temperature T changes.

C、The average speed is always greater than the most probable speed.

D、Two gas systems have the same distribution of speeds if they are at the same temperature.

Part B (10 points)

You are going to read a list of headings and a text about what parents are supposed to do to guide their children into adulthood. Choose a heading from the list A—F that best fits the meaning of each numbered part of the text (41—45). The first and last paragraphs of the text are not numbered. There are two extra headings that you do net need to use. (10 points)

Glass, in one form. or another, has long been in noble service to humans. As one of the most widely used of manufactured materials, and certainly the most versatile, it can be as imposing as a telescope mirror the width of a tennis court or as small and simple as a marble rolling across dirt.

(41)______.

The uses of this adaptable material have been broadened dramatically by new technologies: glass fiber optics—more than eight million miles—carrying telephone and television signals across nations; glass ceramics serving as the nose cones of missiles and as crowns for teeth; tiny glass beads taking radiation doses inside the body to specific organs; even a new type of glass fashioned of nuclear waste in order to dispose of that unwanted material.

(42)______.

On the horizon are optical computers. These could store programs and process information by means of light—pulses from tiny lasers—rather than electrons. And the pulses would travel over glass fibers, not copper wire. These machines could function hundreds of times faster than today's electronic computers and hold vastly more information. Today fiber optics are used to obtain a clearer image of smaller and smaller objects than ever before—even bacterial viruses. Anew generation of optical instruments is emerging that can provide detailed imaging of the inner workings of cells. It is the surge in fiber optic use and in liquid crystal displays that has set the U.S. glass industry (a 16 billion dollar business employing some 150,000 workers) to building new plants to meet demand.

(43)______.

But not all the glass technology that touches our lives is ultra-modem. Consider the simple light bulb; at the turn of the century most light bulbs were hand blown, and the cost of one was equivalent to half a day's pay for the average worker. In effect, the invention of the ribbon machine by Coming in the 1920s lighted a nation. The price of a bulb plunged. Small wonder that the machine has been called one of the great mechanical achievements of all time. Yet it is very simple: a narrow ribbon of molten glass travels over a moving belt of steel in which there are holes. The glass sags through the holes and into waiting moulds. Puffs of compressed air then shape the glass. In this way, the envelope of a light bulb is made by a single machine at the rate of 66,000 an hour, as compared with 1,200 a day produced by a team of four glassblowers.

(44)______.

The secret of the versatility of glass lies in its interior structure. Although it is rigid, and thus like a solid, the atoms are arranged in a random disordered fashion, characteristic of a liquid. In the melting process, the atoms in the raw materials are disturbed from their normal position in the molecular structure; before they can find their way back to crystalline arrangements the glass cools. This looseness in molecular structure gives the material what engineers call tremendous "formability" which allows technicians to tailor glass to whatever they need.

(45)______.

Today, scientists continue to experiment with new glass mixtures and building designers test their imaginations with applications of special types of glass. A London architect, Mike Davies, sees even more dramatic buildings using molecular chemistry. "Glass is the great building material of the future, the 'dynamic skin'", he said". Think of glass that has been treated to react to electric currents go

A.6

B.7

C.8

D.9

A．The average age of the class is 19．

B．I was an average sort of student．

C．The average of 8 , 10, and 12 is 10．

A.6

B.7

C.8

D.9

A.10

B.11

C.12

D.13