英文科學(xué)讀本 第二冊(cè)·Lesson 18 Fusible

Lesson 18 Fusible

Go and get the old iron spoon. Will, said Fred. "We'll have our lesson all over again when Norah comes in."

Away ran Willie, while Fred went to find one or two things he wanted for the lesson, and they were soon ready to begin.

Now, little girl, said Fred, "you have seen me use this iron spoon before. What did I do with it?"

You put a piece of wax in it and held it over the fire, said Norah.

What then? asked Fred.

The wax melted.

What does that mean? he asked again.

The solid wax became liquid wax, and flowed about, said Norah.

I think, too, we have melted something else besides wax, said Will.

Oh yes, said Norah, "we melted sugar in the spoon too."

I want to use the spoon again now. Do you know what this is, Norah? It is a piece of lead, I think," she said.

You are right, sister. It is lead, said Fred. "Now look and see what happens when I put this lead in the spoon, and hold it over the fire."

The lead has melted and the liquid flows about in the spoon just as the other things did, said Norah.

Yes, it has melted, said Fred. "Teacher gave us a new name today for this melting. We may say we melt the lead or fuse it. Fuse and melt mean the same."

Yes, and the things that we can fuse, said Will, joining in, "are fusible. Some things, such as wood, brick, slate, and stone, do not melt with heat. They are said to be infusible—that is, not fusible. Teacher pointed out to us that some of our minerals are useful to us entirely because they are fusible. Like lead, they can all be melted or fused with heat. We call them metals."

Can you tell any of the metals, Norah? said Fred.

Iron and copper are metals as well as lead, said Norah.

Yes, said Will, "and so are gold, and silver, and tin, and zinc."

SUMMARY

Wax melts in a spoon over the fire—the solid becomes a liquid, and flows about. Lead, too, melts in the same way. We say it is fusible. Iron, copper, tin, zinc, silver, and gold will all melt or fuse, like the lead. They are metals.