不可逆变化

解释有些变化会生成新的物质，而且通常不可逆转，例如燃烧、生锈以及与酸的反应。

Explain that some changes result in the formation of new materials and are not usually reversible, such as burning, rusting, and reactions with acid

学习证据 / Evidence

• 将不可逆变化定义为生成无法变回原样的新物质的变化。
• 至少举出三个例子：燃烧、生锈、将小苏打与醋混合。
• 描述不可逆变化中可观察到的迹象：产生气体、颜色变化、放出热量、生成新物质。

• Define an irreversible change as one that creates new materials that cannot be changed back
• Give at least three examples: burning, rusting, mixing bicarbonate of soda with vinegar
• Describe observable signs of irreversible change: gas produced, colour change, heat given off, new substance formed

评估问题 / Assessment

{{name}}能解释为什么不能把一片烤焦的吐司变回原来的样子，或者把铁锈变回闪亮的铁，因为已经生成了全新的物质吗？

Can {{name}} explain why you can't un-burn a piece of toast or turn rust back into shiny iron, because a completely new material has been made?