2012高考英语二轮复习专题限时训练(江苏专用)专题2阅读理解18(35分钟)ATemperatureismeasuredbymeansofathermometer(温度计)
Onegeneralformofthermometerdependsuponthefactthatmostsolidsandliquidsexpandastheirtemperaturerises
Thereareoneortwoexceptions
Thereis,forinstance,akindofsteelcalledinvar(from“invariable”)whichdoesnotchangeitsdimensionsastemperaturechanges;itisvaluableformakingpendulums(钟摆),since,ifthelengthofapendulumchanges,itstimeofvibrationchanges
Itisalsousedformakingveryaccuratemeasuringscales
Inbothcases,then,changesofatmospherictemperaturehavenoeffectifinvarisused
Anotherexceptionisthatveryoddliquid,water,whichhasmanystrangeproperties(特性)
Aswatergetscolderitcontracts(收缩),whichisordinarybehavior,untilitreachesthetemperatureof30℃
abovefreezingpoint
Afterthat,asitgetscolder,itexpands
Thisisfortunate---forconsidering