A:Al2O3熔点高,可用作耐高温材料
B:用米汤检验含碘盐中的碘酸钾
C:用纯碱溶液洗涤餐具上的油污
D:利用丁达尔效应区别蛋白质溶液和食盐水
What do you know about the sea? Some people know about it, but others don’t. The sea looks beautiful on a fine sunny day, the sea is very big. In the world, there is more sea than land. Do you know Hainan Island? It’s really very nice. We can see beaches, trees and the sea. We can swim and visit a lot of beautiful places.
①先裁下了一张长BC=20cm,宽AB=16cm的矩形纸片ABCD,
②将纸片沿着直线AE折叠,点D恰好落在BC边上的F处,
请你根据①②步骤解答下列问题:计算EC,FC的长.
变量控制是化学实验中常用的设计方法.在探究影响不同固体物质在溶剂中溶解限量的因素时,不需要控制的变量是( )