如图所示实验,说明了二氧化碳( )
A.不能燃烧,也不能支持燃烧;密度比空气的大
B.二氧化碳的密度比空气大
C.二氧化碳可与蜡烛发生反应
D.二氧化碳通常为无色无味的气体
将二氧化碳气体慢慢倒入燃着两只蜡烛的烧杯中,观察到的现象是下层的蜡烛火焰先熄灭,上层的蜡烛火焰后熄灭,这是因为CO2密度比空气大,不能燃烧、不能支持燃烧的缘故,根据二氧化碳的上述性质,二氧化碳可以用于灭火.
答案:A.
如图所示实验,说明了二氧化碳( )
A.不能燃烧,也不能支持燃烧;密度比空气的大
B.二氧化碳的密度比空气大
C.二氧化碳可与蜡烛发生反应
D.二氧化碳通常为无色无味的气体
将二氧化碳气体慢慢倒入燃着两只蜡烛的烧杯中,观察到的现象是下层的蜡烛火焰先熄灭,上层的蜡烛火焰后熄灭,这是因为CO2密度比空气大,不能燃烧、不能支持燃烧的缘故,根据二氧化碳的上述性质,二氧化碳可以用于灭火.
答案:A.
完形填空。 | |||
Peter and Paul had got permission from their parents to camp in a field close to their | |||
( )1.A.surprising ( )2.A.went round ( )3.A.load ( )4.A.grassland ( )5.A.live ( )6.A.but ( )7.A.Unconsciously ( )8.A.woods ( )9.A.put off ( )10.A.forward ( )11.A.place ( )12.A.alone ( )13.A.After all ( )14.A.discovered ( )15.A.afraid ( )16.A.enjoyment ( )17.A.appear ( )18.A.behind ( )19.A.fetched ( )20.A.for | B.exciting B.went back B.tent B.destination B.lie B.and B.Unfortunately B.farm B.put on B.near B.mark B.about B.At last B.encouraged B.sure B.satisfaction B.do B.out B.watched B.to | C.annoying C.went away C.food C.field C.wait C.or C.Unwillingly C.setting C.put down C.back C.way C.in C.Above all C.persuaded C.informed C.disappointment C.work C.aside C.followed C.at | D.frightening D.went through D.storage D.river D.stay D.so D.Uninterestingly D.camp D.put up D.further D.time D.on D.At first D.supposed D.reminded D.imagination D.behave D.around D.collected D.in |