托福閱讀考試想要拿高分與平時(shí)的練習(xí)脫不了關(guān)系。出國(guó)留學(xué)網(wǎng)托福欄目小編整理了相關(guān)的資料，希望可以幫助考生度過(guò)考試的難關(guān)，下面是小編搜集的托福閱讀考試練習(xí)經(jīng)典素材：鐘表的發(fā)展的相關(guān)資訊，歡迎參考!
托福閱讀考試練習(xí)經(jīng)典素材：鐘表的發(fā)展
內(nèi)容回憶：
鐘表發(fā)展之初都是手工的，又笨重，又貴，只有有錢人買的起(有考點(diǎn))。后來(lái)有人改進(jìn)了這種鐘表，用木頭造，還設(shè)計(jì)了一些特殊的工具，很多中產(chǎn)階級(jí)就買得起了。 然后后來(lái)他又發(fā)現(xiàn)鐘表太大了， 需要額外買個(gè)柜子放這個(gè)表，他就改進(jìn)鐘表，使之可以掛在墻上。 還申請(qǐng)了專利。 但是還是有很多人模仿他的設(shè)計(jì)(有考點(diǎn))。最后他雇了一個(gè)人，這個(gè)人給鐘表設(shè)計(jì)了很多裝飾。
參考閱讀： Development of the Periodic Table
The periodic table is a chart that reflects the periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number (the number of protons in the nucleus). It is a monumental scientific achievement, and its development illustrates the essential interplay between observation, prediction, and testing required for scientific progress. In the 1800's scientists were searching for new elements. By the late 1860's more than 60 chemical elements had been identified, and much was known about their descriptive chemistry. Various proposals were put forth to arrange the elements into groups based on similarities in chemical and physical properties. The next step was to recognize a connection between group properties (physical or chemical similarities) and atomic mass (the measured mass of an individual atom of an element). When the elements known at the time were ordered by increasing atomic mass, it was found that successive elements belonged to different chemical groups and that the order of the groups in this sequence was fixed and repeated itself at regular intervals. Thus when the series of elements was written so as to begin a new horizontal row with each alkali metal, elements of the same groups were automatically assembled in vertical columns in a periodic table of the elements. This table was the forerunner of the modern table.
When the German chemist Lothar Meyer and (independently) the Russian Dmitry Mendeleyev first introduced the periodic table in 1869-70, one-third of the naturally occurring chemical elements had not yet been discovered. Yet both chemists were sufficiently farsighted to leave gaps where their analyses of periodic physical and chemical properties indicated that new elements should be located. Mendeleyev was bolder than Meyer and even assumed that if a measured atomic mass put an element in the wrong place in the table, the atomic mass was wrong. In some cases this was true. Indium, for example, had previously been assigned an atomic mass between those of arsenic and selenium. Because there is no space in the periodic table between these two elements, Mendeleyev suggested that the atomic mass of indium be changed to a completely different value, where it would fill an empty space between cadmium and tin. In fact, subsequent work has shown that in a periodic table, elements should not be ordered strictly by atomic mass. For example, tellurium comes before iodine in the periodic table, even though its atomic mass is slightly greater. Such anomalies are due to the relative abundance of the "isotopes" or varieties of each element. All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass. The isotopes of a given element have the same chemical properties but slightly different physical properties. We now know that atomic number (the number of protons in the nucleus), not atomic mass number (the number of protons and neutrons), determines chemical behavior.
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