例26　We may define chemistry as the subject in which we can observe the chemical change in substance as a result of which it is possible to form a new substance.

【结构分析】这句话是连环定语从句，主干是We may define chemistry as the subject，后面是介词加上定语从句in which we can observe the chemical change in substance，后面再套上介词加上定语从句as a result of which it is possible to form a new substance。

【亮点回放】此句话的亮点在于连环定语从句的超级使用，而且每个定语从句前面都有介词，很有气势。

【核心词汇】

define...as　定义为

chemical change　化学变化

substance　物质

form a new substance　形成一种新的物质

【参考译文】我们把化学定义为这样一种学科，也就是我们可以观察一种化学变化，通过这种化学变化可以生成一种新的物质。