substance

他的演讲内容空洞，缺乏实质性的观点。

His speech was empty and lacked ___substance.

这种物质在高温下会变成液体。

This ___substance turns into liquid at high temperatures.

这种材料看起来很坚固，但其实际物质成分主要是塑料。

This material looks sturdy, but its ___substance is mainly plastic.