There are two kinds of change — chemical change and physical change.
In a chemical change, there is always a new substance formed. Breaking up water into hydrogen (氢气) and oxygen is a chemical change. In each of the chemical change at least one new substance (物质) is formed. A change is not a chemical change if it doesn’t form a new substance.
Physical changes are very common, too. There are many examples.You can make a physical change by tearing (撕扯) a piece of paper into two, or by cutting a piece of iron with a lathe (车床). Here the paper is still paper, and the iron is still iron.
Another way of making physical change is dissolving (溶解) something in water. When you dissolve salt in water, the salt disappears. You may think that a new substance has been formed. But in fact there is no new substance. The salt is still salt. You can still taste it. So the dissolving of anything is a physical change.
When water freezes, the change is also a physical one.The water changes from liquid to solid. But it is still the same substance. That is why the freezing of anything is a physical change.
And people often tell the differences between a chemical change and a physical change through some experiments. In this module, let’s explore the magical science world by doing experiments by ourselves.
Section_ⅠIntroduction & Reading — Pre-reading
[原文呈现],
Passage A ①[读文清障] It’s hard to think of a world without metals. Different ①think of 想出；想象 metals have different uses， for example, steel is used in 句中 it 是形式主语，真正的主语是 to think cars, and iron is used in electricalequipment. When we use of ... metals, it is important to know how they react with different ②use n．用途；功能，此处为可数名词。 substances， for example, water and oxygen. The reaction⑦⑧⑤⑥③④②③electrical/I’lektrIkl/adj.与电有关的；用电 of metals with these substances can be put in order. Here 的 ⑨10，is a table with the metals that react most at the top○ and ④equipment/I’kwIpm?nt/n．设备；装备，the metals that react least at the bottom?. Metal Potassium Sodium Calcium Magnesium Aluminium Zinc Iron Copper Reacts slowly Partial? reaction Partial reaction No reaction Burns to form?不可数名词 ⑤react /ri’?kt/vi.(化学)反应 react with 与……起反应 substance/’s?bst?ns/n．物质 when 引导时间状语从句，主句中 it 是形式主语，不定式短语是真正的主语； how引导or steam? Heated in oxygen Reaction with water Reacting with cold water Reacting with steam an oxide? 宾语从句。 ⑥oxygen/’?ksId??n/n．氧气 ⑦reaction/ri’?k?n/n．反应 reaction with 与……的反应 ⑧put ...in order 把……按顺序排列 ⑨metal n．金属 ⑩at the top 在顶端 ?at the bottom 在底部 Here is a table ...是完全倒装句；that引导定语从句，修饰metals。 ?form/f??m/vi.形成 ?oxide/’?ksaId/n．氧化物 ?partial/’pa??l/adj.部分的；局部的 ?steam /sti?m/n．蒸汽；水汽 * an oxide ＝ another substance ＋ oxygen A篇
[课文译文]
很难想象一个没有金属的世界。不同的金属有不同的用途，例如，钢材被用于汽车中，铁被用于电器设备中。当我们使用金属时，了解它们和不同的物质如何发生反应是很重要的，比如，水和氧气。(不同的)金属与这些物质的反应程度可以按顺序排列起来。右面表格中的金属反应最强的排在上面，反应最弱的排在下面。
金属 钾 钠 钙 镁 铝 锌 铁 铜 * 氧化物＝另一种物质＋氧气
Passage B
A Simple Scientific Experiment Below is a description of a simple scientific experiment. It shows us how iron reacts with air and with water?. Aim?： To find out? if iron rusts? (a) in dry air; (b) in water that has no air in it
21 water); (c) in ordinary○22 water. (air-free○
23； test tubes; Apparatus: 3 clean iron nails○
?
在有氧状态下加热 与水或水蒸气的反应 与冷水反应 燃烧后生成氧化物 与水蒸气反应 反应缓慢 部分反应 部分反应 不反应 ?Below is a description ... 是完全倒装句。 ?iron n．铁
how 引导的宾语从句和us一起作 show 的双宾语。
?aim/eIm/n．目标；目的 ?find out 弄清 ?rust/r?st/vi.生锈
21air-○free adj.没有空气的
22ordinary/’??dn?ri/adj.普通的；平常的 ○
23nail n．钉子 ○
24down prep.沿着 ○
25leave vt.使……处于某状态、某地等 ○
test tube holder; cotton wool; oil; Bunsen burner.
Iron in dry air Method
(1)Put some iron nails at the bottom of a test tube.
24 the tube. (2)Push some cotton wool down○25 the tube for one week. (3)Leave○
leave＋宾语＋adj.使……处于某种状态。
26conclusion/k?n’klu??n/n．结论 ○
Result
After one week, the nails have not rusted.
26 Conclusion○
Iron does not rust in dry air.
B篇
[课文译文]一个简单的科学实验
下面是对一个简单科学实验的描述。这篇文章向我们表明，铁是怎样与空气和水反应的。
目的：弄清楚铁是否会在下列状态下生锈：(a)在干燥的空气中；(b)在没有空气的水中(无空气水)；(c)在普通的水中。
仪器：三颗洁净的铁钉，试管，试管夹，棉花，油，本生灯(即煤气灯)。 铁在干燥的空气中 方法
(1)把若干铁钉置于试管底部。(2)顺着试管塞入一些棉花。(3)把试管放置一周。 结果
一周后，铁钉未生锈。 结论
铁在干燥的空气中不生锈。
Iron in air-free water Method
(1)Half-fill a test tube with water.
27 the water for three minutes. (2)Boil○
28 there is no air in the (This makes sure○
27boil/b?Il/vt.煮；煮沸 ○
28make sure 确保，其后省略了宾语从句的引○
导词 that。
29add ...to ...往……加入…… ○
30keep ...out of 防止……进入；使……在外面 ○
water.)
(3)Put two or three clean nails in the water.
29 the water. This will (4)Add some oil to○30 the water. keep air out of○
(5)Leave the tube for one week. Result
The nails do not rust in the tube with
air-free water.
Conclusion
Iron does not rust in air-free water. Iron in ordinary water Method
(1)Half-fill a test tube with water and add two or three clean nails.
(2)Leave the tube for one week. Result
The nails rust in the tube with ordinary water.
Conclusion
Iron rusts in ordinary water.
[课文译文]
铁在不含空气的水中 方法
(1)在试管中加一半水。
(2)将水烧开保持3分钟。(这样做可以保证水中无空气。) (3)在水中放2～3颗洁净的铁钉。
(4)在水中加些油，这样做可防止空气进入水中。 (5)把试管放置一周。 结果
铁钉在装有无空气的水的试管中未生锈。 结论
铁在没有空气的水中不生锈。 铁在普通的水中 方法
(1)在试管中加一半水，并在水中放2～3颗洁净的铁钉。 (2)把试管放置一周。 结果
铁钉在装有普通水的试管中生锈。 结论
铁在普通的水中会生锈。