chocolate什么时候是可数名词什么时候是不可数名词

例句：

He broke the bar of chocolate in two and gave me half.

他把巧克力掰成两半，给了我一块。

When I was young chocolate was a treat.

我年轻的时候，吃巧克力是一种难得的享受。

He broke the chocolate in two.

他把那块巧克力一分为二。

Two coffees and a hot chocolate, please.

请来两杯咖啡和一杯热巧克力。

Don't stuff the kids with chocolate before their dinner.

正餐前不要给孩子一个劲地吃巧克力。