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化学变化在生产和生活中普遍存在。产生了新物质的变化是化学变化,如铁的生锈、节日的焰火、酸碱的中和、镁条的燃烧等等。那么,美国课堂上是如何讲解化学变化的呢?When the iron present in nails,cars,or bridges is ex-posed to air,it comes in contact with oxygen.Iron and oxy-gen combine to make a new powdery,reddish-brown substancecalled rust.How do we know it is a new substance?Rustis a new substance because it has its own properties.
Chemical changes are ubiquitous in production and life. The resulting new material changes are chemical changes, such as iron rust, festival fireworks, acid-base neutralization, magnesium bar burning and so on. So the iron present in nails, cars, or bridges is ex-posed to air, it comes in contact with oxygen. Iron and oxy-gen combine to make a new powdery, reddish-brown substancecalled rust.How do we know it is a new substance? Rustis a new substance because it has its own properties.