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प्रश्न
Write scientific reason.
Coins are made from metals and alloys.
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उत्तर
- Coins are made from metals and alloys because metals and their alloys possess the property of malleability. So, they can be hammered into flat shape without breaking.
- Metals and alloys used for making coins should be corrosion resistance and bright in colour. They should also be hard and wear resistance.
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संबंधित प्रश्न
What are alloys?
Choose the correct answer from the options given below:
Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as
A. Smelting
B. Ore-dressing
C. Calcination
D. Bessemerisation
What is anodising? Give its applications.
The chemical reaction involved in the corrosion of iron metal is that of ______.
Explain why, iron sheets are coated with zinc.
The corrosion of iron is called ______.
Tiffin boxes are electroplated with ______ but car bumpers are electroplated with ______ to protect them from rusting.
______ and ______ are necessary for the rusting of iron.
Explain why, though aluminium is more reactive than iron, yet there is less corrosion of aluminium when both are exposed to air.
Give the constituents of brass.
Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Name a common metal which is highly resistant to corrosion.
In stainless steel alloy, iron metal is mixed with ______.
Bronze is an alloy of ______.
Name the metal which is a constituent of plant pigment?
State under what conditions corrosion is faster ?
What are the adverse effects of corrosion?
Give reason for the following:
A suspension of rust is basic in nature.
Corrosion of silver causes a black layer of _______.
Stainless steel is an alloy of _______.
Bronze : _______ : : Stainless steel : Fe + Cr + C
Find the odd one out and give its explanation.
Find the odd one out and give its explanation.
Match the columns.
| Group A | Group B |
| 1) Electroplating | a) Pressure cooker |
| 2) Anodising | b) Silver plated spoons |
| c) Coating of tin on copper | |
| d) Coating of Zinc on iron |
Explain concept with example/explain with the help of a balanced equation.
Corrosion
Draw a neat labelled diagram.
Anodizing
Observe the following diagram and write answers.
- Name the method.
- Explain the method.
- Give two examples of this method.
The process of coating the surface of the metal with a thin layer of zinc is called ______
What is rust?
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
Amalgam is an alloy of ____________.
Identify the correct statement from the following:
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
State whether the following statement is true or false:
Ships suffer a lot of damage though they are painted.
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Explain the following:
Bubbles are produced when acetic acid is added to a solution of sodium hydrogencarbonate.
Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?
