Object lessons in elementary science; following the scheme issued by the London School Board Volume 1 - Tapa blanda

Sinopsis

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 edition. Excerpt: ... hold it in our warm hands; tallow and butter before fire; wax, sugar, sulphur melt readily over the flame of the lamp; but glass, lead, and all the metals require more heat before they will change into the liquid form. III. Solders The metals all differ from one another in their fusibility. Some require much more heat than others, to fuse. Tin is the most easily fused of metals. Lead is also easily fused, but iron, copper, silver, gold require great heat. Some metals when in the liquid state are mixed together and then allowed to cool. They are then called alloys. When an alloy is made of two metals it is more easily fusible than either. That is to say, less heat melts the alloy than either of the metals of which it is made. The handle is broken off the tin teapot. The tinman mends it with an alloy of lead and tin, called solder. The alloy or solder melts more easily than the tin of teapot. In other words, lie knows he can put the hot, melted solder on the pot without the chance of melting the tin. N.B.--The metals mercury, potassium, and sodium are purposely excluded here. Lesson VIII SOME MORE ABOUT METALS Gall on the children to name the metals mentioned in the last lesson. Make them tell that they are all minerals--they are dug out of the earth; that they have all one common property--they are fusible; but that some melt more easily than others, tin and lead being the most fusible, iron and gold the most difficult to melt. Show some specimens of each, and lead Hie class to work out the following properties:--I. Lustrous Call attention to some object made of bright steel. Explain that steel is highly prepared iron. Note its bright, polished surface. Rub it with a piece of washleather. The more we rub, the brighter it shines. We say...

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