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Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?

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प्रश्न

Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?

संक्षेप में उत्तर
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उत्तर

1. Rusting of Iron:

  • Why Harmful: Rusting weakens iron and steel structures, leading to potential failures and increased maintenance costs.
  • Prevention: Apply protective coatings like paint or use galvanization (coating with zinc) to prevent exposure to moisture and oxygen.

2. Food Spoilage:

  • Why Harmful: Spoiled food can cause food poisoning and waste valuable resources.
  • Prevention: Store food properly in cool, dry places, use refrigeration, and adhere to proper hygiene practices to slow down spoilage.
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अध्याय 5: Physical and Chemical Changes - Activities and Projects [पृष्ठ ५६]

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एनसीईआरटी Science [English] Class 7
अध्याय 5 Physical and Chemical Changes
Activities and Projects | Q 1. | पृष्ठ ५६

संबंधित प्रश्न

Two methods by which rusting of iron can be prevented are ______ and ______.


State two conditions for the rusting of iron.


What are the constituents of stainless steel?


No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.

  1. What could the solids A and B be?
  2. What are the products C and D most likely to be?
  3. Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.
  4. What is the special name of such a reaction? State one use of such a reaction.
  5. Name any two types of chemical reactions under which the above reaction can be classified.

Corrosion can be an advantage in some case.Explain ?


Complete the process of iron rusting by filling the blanks. Suggest a way to prohibit the process.
The iron rust is formed due to........................... reaction. Different
regions on iron surface become anode and cathode.
 Reaction on anode region :

`F_e(s) → Fe^(2+) (aq) +2e^-`

 Reaction on anode region :

`O_2(g) + 4H^+(aq) +............................ → 2H_2 O (l) `

When Fe2+ ions migrate from anode region they react with ................... to form Fe3+ ions.
A reddish coloured hydrated oxide is formed from ............... ions. It is called rust.

`2Fe_(3+) (aq) + 4H_2O(l) → ................. + 6H_+(aq) `

A way to prevent rusting ..................................................................

 

 


Write three methods of preventing rusting of iron.


Observe the following picture and answer the following questions:

  1. What is rust?
  2. Write the chemical formula of rust.
  3. Write the reaction of oxidation of iron at the anode.
  4. Write the reaction of oxidation of iron at the cathode.
  5. What is corrosion?

Write scientific reason.

Coins are made from metals and alloys.


Observe the following diagram and write answers.

  1. Name the method.
  2. Explain the method.
  3. Give two examples of this method.

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