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111Module 5A Lesson in a Lab话题导入人类从日常生活到宇宙探索都离不开科学技术。如果没有科学的发展,我们将仍然处于愚昧无知的原始状态,科学技术是第一生产力,它推动了社会经济、文明的发展,使我们人类成为了宇宙的主人。作为中学生,我们应该以“八荣八耻”中的“以崇尚科学为荣、以愚昧无知为耻”为行为准则,把智慧和热情投入到科学研究和探索中。 背景资料什么是铁？铁位于周期表第四周期第族。元素符号为Fe,原子序数为26,是一种重要的过渡元素。光亮的银白色金属,密度7.86gcm3,熔点1535,沸点2750。纯铁的抗蚀力相当强,但通常的铁都含有碳和其他元素,因而使它的熔点降低,抗蚀力也减弱。铁有延展性和导热性，也能导电。但导电性比铜、铝都差。铁能被磁体吸引,在磁场作用下,铁自身也能产生磁性。铁为什么会生锈？铁放的时间长了就会生锈。铁容易生锈,除了由于它的化学性质活泼以外,同时与外界条件也有很大关系。水分是使铁容易生锈的物质之一。然而,光有水也不会使铁生锈,只有当空气中的氧气溶解在水里时,氧在有水的环境中与铁反应,才会生成一种叫氧化铁的东西,这就是铁锈。铁锈是一种棕红色的物质,它不像铁那么坚硬,很容易脱落,一块铁完全生锈后,体积可胀大8倍。如果不除去铁锈,这海绵状的铁锈特别容易吸收水分,铁也就烂得更快了。引入型阅读Chemical Change and Physical ChangeThere are two kinds of changeschemical change and physical change.In a chemical change,there is always a new substance formed.Breaking up water into hydrogen and oxygen is a chemical change.In each of the chemical change at least one new substance is formed.A change is not a chemical change if it doesnt form a new substance.Physical changes are very common,too.There are many examples.You can make a physical change by tearing a piece of paper in two,or by cutting a piece of iron with lathe.Here paper is still paper,and the iron is still iron.Another way of making physical change is dissolving something in water.When you dissolve salt in water,the salt disappears.You may think that a new substance has been formed.But really 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.1.It is not _if a new substance is not formed in the change.A.a physical changeB.a chemical changeC.change of stateD.a change2.The dissolving of salt in water is _.A.a physical changeB.a chemical changeC.hydrogen and oxygenD.breaking up3.The change of the three states of water is _.A.a chemical changeB.different substancesC.a physical change D.the same state 答案:1.B2.A3.C 111
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