When heated or taken into the warm room ice soon changes into water.
问题描述：
When heated or taken into the warm room ice soon changes into water.
（ 为什么在v.-ed作状语的情况下,when不去掉呢?）
答
When（主+被动词） heated or taken into the warm room ,ice soon changes into water.
【,】前面是从句,when是连词,【,】后面是主句,主从复合句怎么能省略连词
从句里面（）部分才是可以省略的那为什么seen under a microscope，a fresh snow flake has a delicate six-pointed shape 这可以把when也省了呢？其实状语从句（主从句主语不变）都可以改成分词作状语，我现在觉得你原来那句的确可以改成状语从句了，但是时态要发生变化吧。