压缩

Will it all fit?
::都合适吗?

When we pack to go on vacation, there is always “one more” thing that we need to get in the suitcase. Maybe it’s another bathing suit, pair of shoes, book – whatever the item, we need to get it in. Fortunately, we can squeeze things together somewhat. There is a little space between the folds of clothing, we can rearrange the shoes, and somehow we get that last thing in and close the suitcase.
::当我们打包去度假时,我们总是需要“再做一件”的东西。 也许这是另一件泳衣、一双鞋、一本书 — — 不管是什么东西,我们都需要把它放进去。 幸运的是,我们可以把东西挤在一起。 衣服的折叠之间有一点点空间,我们可以重新排列鞋子,我们也可以把最后一件衣服放在箱子里,把箱子关上。

Compressibility
::压缩

Scuba diving is a form of underwater diving in which a diver carries his own breathing , usually in the form of a tank of compressed air. The pressure in most commonly used scuba tanks ranges from 200 to 300 atmospheres. Gases are unlike other in that a gas expands to fill the shape and volume of its container. For this reason, gases can also be compressed so that a relatively large amount of gas can be forced into a small container. If the air in a typical scuba tank were transferred to a container at the standard pressure of 1 atm, the volume of that container would need to be about 2500 liters .
::潜水是一种水下潜水形式,潜水员自行呼吸,通常以压缩空气罐的形式进行,最常用的潜水罐的压力在200至300个大气层之间,气体与其他气体不同,因为气体会膨胀以填充容器的形状和体积,因此,气体也可以压缩,这样就可以将相对大量的气体强迫进入一个小容器。如果典型潜水罐中的空气在1小时的标准压力下被转移到一个容器,那么容器的容量就需要大约2500升。

Compressibility is the measure of how much a given volume of matter decreases when placed under pressure. If we put pressure on a solid or a , there is essentially no change in volume. The atoms, , or molecules that make up the solid or liquid are very close together. There is no space between the individual particles, so they cannot pack together.
::压缩度是测量在压力下某一物质体积减少多少。 如果我们对固体或一个物质施压, 其体积基本上没有变化。 构成固体或液体的原子、 或分子非常接近。 单个粒子之间没有空间, 所以它们无法组合在一起 。

The kinetic-molecular theory explains why gases are more compressible than either liquids or solids. Gases are compressible because most of the volume of a gas is composed of the large amounts of empty space between the gas particles. At room temperature and standard pressure, the average distance between gas molecules is about ten times the diameter of the molecules themselves. When a gas is compressed, as when the scuba tank is being filled, the gas particles are forced closer together.
::动能分子理论解释了为什么气体比液体或固体都更压缩。气体是压缩的,因为气体的体积大部分是由气体粒子之间的大量空隙构成的。在室温和标准压力下,气体分子之间的平均距离大约是分子本身直径的十倍。当气体压缩时,如在填充蒸气罐时,气体粒子被逼近。

Compressed gases are used in many situations. In hospitals, oxygen is often used for patients who have damaged lungs to help them breathe better. If a patient is having a major operation, the anesthesia that is administered will frequently be a compressed gas. Welding requires very hot flames produced by compresses acetylene and oxygen mixtures. Many summer barbeque grills are fueled by compressed propane.
::许多情况下都使用压缩气体。在医院,对肺部受损的病人经常使用氧气来帮助他们呼吸。如果病人进行大规模手术,则所服用的麻醉往往是一种压缩气体。焊接需要由压缩乙炔和氧混合物产生的非常热的火焰。许多夏季烧烤炉用压缩丙烷作为燃料。

Summary
::摘要

播放段落
• Gases will compress more easily than solids or liquids because there is so much space between the gas molecules.
  ::气体的压缩将比固体或液体更容易,因为气体分子之间有很大的空间。

Review
::回顾

播放段落
1. Why is there no change in volume when pressure is applied to liquids and solids?
   ::当对液体和固体施压时,体积为何没有变化?
播放段落
2. Why do gases compress more easily than liquids and solids?
   ::为什么气体压缩比液体和固体更容易?
播放段落
3. List uses for compressed gases.
   ::压缩气体用途清单。