英文科學(xué)讀本 第一冊(cè)·Lesson 04 Liquids and Solids

Lesson 04 Liquids and Solids

When the boys, a few nights later, called Norah to come and play school, Fred said: "I want to be teacher this time. I am going to show Norah what we have been doing in school to-day. Mother gave me this piece of wax, and said I might have this old iron spoon.

Now I will put the wax into the spoon, said Fred. "See; it stands in the middle of the spoon.

I want you to watch what happens, when I hold the spoon over the fire.

Why, the solid wax is changing into a liquid, said Norah.

How do you know it is a liquid, Norah?

It does not stand up in a lump in the middle of the spoon, as it did at first, said Norah. "It flows about in the spoon. It keeps a level surface."

See, said Fred, "I will pour some of it into this pill-box, just as teacher did today, and stand the box on the table."

That is just what we saw, Norah, when the meat was roasting the other day, said Will.

Yes, said Norah, "the solid fat was changed into liquid, and fell in drops into the dish. I took it up in the spoon, and poured it over the meat to baste it."

Don't you two children chatter so, said Fred. "I want to have a look at our pill-box.

See, Norah, the wax is cool now. It does not flow about, even if we turn it upside down. It is not a liquid now. Suppose I cut the box open." said Fred. "Look; here is a round piece of solid wax, the very shape of the box."

Why, Fred, said Norah, "this proves that liquids do really take the shape of the vessels which hold them."

Quite right, clever little sister, said Fred. "Now tell me what mother does with the liquid fat in the dripping-pan."

She pours it into a basin, said Norah; "When it is cold she turns it out as solid dripping, just the shape of the basin."

I saw some solid water in a basin the other day. said Will. "We call it ice. The cold weather changed the water into ice. When I put the basin on the hearth, the solid ice turned into water again."

You can't change everything like this, said Fred.

No, said Norah, "we can't change brick, wood, stone, or slate into liquids."

SUMMARY

Wax is a solid. We can change it into a liquid over the fire. The fire melts the wax. When it gets cold it becomes solid again. Ice is solid water.