Elements: Metals and Nonmetals
Matt was a grade 7 student at Wills High school. He was mesmerized by science. One day he was given a bar magnet by his father. His father told him that he can attract metals with the help of the bar magnet. From then onwards, Matt began to unearth metallic objects from his backyard using his bar magnet. He began to be interested in metals and non-metals. He had a conversation with his science teacher, Mr. Johnson, on this topic.
Matt: Good morning, Mr. Johnson. See here. I have got an iron ring from my yard.
Mr. Johnson: Very interesting Matt. As you know iron is a metal. Do you know that metals and non-metals together are called elements?
Matt: Really? Please tell me more.
Mr. Johnson: Sure. Ask me your questions.
Matt: Are elements classified into metals and non-metals?
Mr. Johnson: Yes. And they are as different from each other as day and night.
Matt: Can I guess a difference? Aren’t metals shiny and non-metals dull?
Mr. Johnson: Excellent. Secondly, in what state do you find metals usually? Solid, liquid or gas?
Matt: Solid.
Mr. Johnson: So that is the second difference. Non-metals are mostly gases and liquids.
Matt: Do they conduct electricity? Any difference there?
Mr. Johnson: Good question. Metals conduct electricity very well. But in the case of non-metals, electrical conductivity is usually poor.
Matt: Is it the same with heat conductivity?
Mr. Johnson: Yes, Matt. While the electrical conductivity of metals is good, that of non-metals is poor.
Matt: Do metals boil and melt at a high temperature?
Mr. Johnson: Yes, they do. But in the case of non-metals the boiling and melting point is usually low.
Matt: How about density?
Mr. Johnson: Oh yes. Metals have high density while non-metals have low density.
Matt: Very interesting. I have seen that metals are used in many places. For example, iron is used to build a gate or a grille. Are non-metals also used like that?
Mr. Johnson: Not really. Metals are malleable and ductile. That is why they can be used to make tools and other useful things.
Matt: What do you mean by malleable, Mr. Johnson?
Mr. Johnson: Malleable means can be beaten into sheets and moulded.
Matt: And how about ductile?
Mr. Johnson: Ductile means can be drawn into wires without breaking.
Matt: Oh, I see. Let me guess. Non-metals are not malleable and not ductile.
Mr. Johnson: You guessed right. Non-metals are brittle. I mean, if they are solids.
Matt: I am sorry, Mr. Johnson. What is ‘brittle’?
Mr. Johnson: Brittle means can snap or break easily.
Matt: Oh, I see. Mr. Johnson, usually the metals I have seen are all solids. Are there any metals that are not solid?
Mr. Johnson: Yes, Matt. Mercury is a metal that is in liquid state at normal temperature. What’s more, it has a low melting point too.
Matt: Wow! Very interesting. Are there any other exceptions like that?
Mr. Johnson: Yes. The metal Gallium. It is a brittle solid. I mean at room temperature. However, mind you, it melts when held in the palm of your hand.
Matt: Oh, I see. How about graphite Mr. Johnson? I have read somewhere that it is a non-metal but can conduct electricity.
Mr. Johnson: Yes, you are right. It is a very curious case of a non-metal conducting electricity.
Matt: It is so interesting to learn about elements. Is copper an element?
Mr. Johnson: Yes, Matt. It is a metallic solid. It is reddish-brown.
Matt: I think electric wires are made of copper. Am I right? It must be because it is a good conductor of electricity. Am I right?
Mr. Johnson: Yes. What’s more, it is ductile and resistant to corrosion. It is strong too.
Matt: No wonder it is so useful to us.
Mr. Johnson: Can you think of another element that is a good conductor of heat and electricity?
Matt: How about Silver?
Mr. Johnson: Excellent! Silver is a shiny, metallic solid. And it is ductile.
Matt: So that is why it is used to make cutlery. Right?
Mr. Johnson: Yes. It is also used to coat glass to make mirrors.
Matt: Fascinating!
Mr. Johnson: It is great to talk to you about science. Matt. We will continue this discussion tomorrow. I have a class now. See you.
Matt: Thank you, Mr. Johnson. See you.