【单选题】下列应用化学科学对物质进行研究的基本方法或所得的结论,错误的是 [ ]
A.
氢气和甲烷的密度都比空气的小,所以都可用向下排气法收集
B.
配制溶质质量分数一定的溶液时,所用的烧杯必须是干燥的
C.
蜡烛燃烧后质量变小,说明质量守恒定律不是普遍规律
D.
通过测定两种稀盐酸的pH,可以比较它们的酸性强弱
【单选题】She was scared the yard because she was scared by the big dog at the gate. [ ]
A.
to go into; to be bitten; lay
B.
of going into; to bite; laying
C.
of going into; to be bitten; lay
D.
to go into; of being bitten; lying:
【单选题】. Seeing the ______ flood, she was _____ to take the boat.
【单选题】She was scared to __________ death when she heard the news.
【单选题】She was scared _______ when hearing the sound of explosion.
【单选题】下列应用化学学科研究物质性质的基本方法或所得结论中,不正确的是 ( )
A.
根据物质的元素组成,将纯净物分为单质和化合物
B.
通过镁、锌、铁分别与稀盐酸反应的实验现象,比较不同金属的活泼性强弱
C.
根据铁制品表面的锈可用稀盐酸溶解除去的事实,说明铁锈主要成分是酸性氧化物
D.
打开盛装浓盐酸的试剂瓶塞,观察现象,了解盐酸的某些物理性质