1. Why cannot a copper wire be used to make elements in electric heater?
A. Copper melts at 108.30C and forms a black powder on reacting with atmospheric oxygen. For heater elements a metal should have more resistance to produce heat.
2. Why is a metal tyre heated before it is fixed on wooden wheels?
A. On heating, the metal tyre expands by which its circumference also increases. This makes fixing the wheel easier and therefore cooling down shrinks it; thus fixing the tyre tightly.
3. Why does the mass of an iron increase on rusting?
A. Because rust is hydrated ferric oxide which adds to the mass of the iron rod. The process of rusting involves addition of hydrogen and oxygen elements to iron.
4. After which chemical element is Argentina named?
A. Silver
5. Which metal is heavier, silver or gold?
A. Gold
6. Which quality of iron ore is best based upon iron content?
A. Magnetite, followed by hematite>Limonite>Siderite
7. Which metals are used to make electrical wires?
A. Copper and Aluminium
8. Which metal is liquid at room temperature?
A. Mercury
9. Which metals are poor conductor of heat and electricity?
A. Mercury and Tungsten
10. Which metals are called soft metals?
A. Sodium and Potassium
11. Which metals are used for making jewellery?
A. Gold, Silver and Platinum
12. Which metal is highly reactive?
A. Sodium
13. Which metals are not malleable and ductile?
A. Zinc, Arsenic and Antimony
14. Which metals have low melting and boiling points?
A. Sodium, Potassium and Mercury
15. Which metals have low densities?
A. Sodium and Potassium
16. Which metals are best conductor of heat?
A. Silver and Copper
17. Which metals are highly malleable metals?
A. Gold and Silver
18. Which metals are called noble metals?
A. Gold and Platinum
19. Which was the first metal to be used by man?
A. Copper.
20. Which one of the following metals has the highest density?
A. Platinum
21. The first metal used by man was
A. Copper
22. Why do you heat a metal rim before fitting it to a wheel?
A. By heating, the rim expands and fits easily over a slightly bigger radius than that of the rim. On being cooled it contracts and has a firm grip on the wheel.
23. How would you distinguish between welding and soldering?
A. Welding is the joining of metals by raising the temperature of the metals to fuse them together by melting their ends. Soldering is the joining of metals with the help of an alloy called solder.
24. A metal tea-pot has an ebony handle. Why?
A. Ebony being bad conductor of heat, the handle does not get hot.
25. What is a meteorite made of?
A. Most meteorites contain at least some iron metal (actually an alloy of iron and nickel). You can see the metal shining on a broken surface. Iron meteorites are all metal, stony iron meteorites are about half metal, half stone, and stone meteorites contain small flecks of metal.
26. What's the only metal that's not a solid at room temperature?
A. Mercury.
27. What process involves heating an ore to obtain a metal?
A. Smelting.
28. What's the most malleable metal?
A. Gold.
29. What substance nets recyclers the most money?
A. Aluminum.
No comments:
Post a Comment