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प्रश्न
Metals are said to be shiny. Why do metals generally appear to be dull? How can their brightness be restored?
उत्तर
Metals, when exposed to air for a long time, become dull due to the formation of a thin layer of oxides, carbonates or sulphides on their surfaces. This is because they react with various gases present in the atmosphere. This is why metals corrode. But their brightness can be restored by rubbing them with a sand paper. Then the outer corroded layer of the metals is removed and they become shiny again.
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संबंधित प्रश्न
The electronic configurations of three elements X, Y and Z are:
| X : 2 | Y : 2, 8, 7 | Z : 2, 8, 2 |
Which of the following is correct regarding these elements?
(a) X is a metal
(b) Y is a metal
(c) Z is a non-metal
(d) Y is a non-metal and Z is a metal
What is an amalgam? How does an amalgam different from an alloy?
Name:
a non metal which is lustrous
Name two metals which react with cold water.
Make pairs of substances and their properties
| Substance | Property |
| a. Potassium bromide (KBr) | 1. Combustible |
| b. Gold | 2. Soluble in water |
| c. Sulphur | 3. No chemical reaction |
| d. Neon | 4. High ductility. |
Write scientific reason.
Copper and brass vessels are cleaned with lemon.
_______ is good conductor of heat but bad conductor of electricity.
Distinguish between:
Metals - Nonmetals (physical characteristics)
Reason out
Sulphur is used in the vulcanization of rubber.
