(a) Define corrosion.

(b) What is corrosion of iron called?

(c) How will you recognise the corrosion of silver?

(d) Why corrosion of iron is a serious problem?

(e) How can we prevent corrosion?

Q: (a) Define corrosion. (b) What is corrosion of iron called? (c) How will you recognise the corrosion of silver? (d) Why corrosion of iron is a serious problem? (e) How can we prevent corrosion?

(a) **Corrosion:** Corrosion is the slow, progressive degradation and eating up of a metal's surface due to its chemical reaction with atmospheric gases, moisture, or acids. (b) **Corrosion of iron:** The corrosion of iron is specifically called **rusting**. (c) **Corrosion of silver:** Silver corrosion is recognized by the formation of a **black coating** on the surface of silver articles when exposed to air, which is due to the formation of silver sulphide ($\text{Ag}_2\text{S}$). (d) **Why iron corrosion is a serious problem:** Iron is the most widely used structural metal in bridges, ships, railway tracks, automobiles, and buildings. Rusting continuously eats away and structurally weakens these iron objects, leading to catastrophic structural failures and costing billions of dollars annually in damage and replacement. (e) **Prevention of corrosion:** Corrosion can be prevented by isolating the metal surface from air and moisture using the following methods: 1. **Painting, oiling, or greasing** the surface. 2. **Galvanisation** (coating iron or steel with a thin protective layer of zinc). 3. **Anodising** (forming a thick, protective oxide layer on metals like aluminium). 4. **Alloying** (mixing the metal with other metals or non-metals to change its properties).

Metals and Non-metals

Corrosion

Official Answer

(a) Corrosion: Corrosion is the slow, progressive degradation and eating up of a metal's surface due to its chemical reaction with atmospheric gases, moisture, or acids.

(b) Corrosion of iron: The corrosion of iron is specifically called rusting.

(c) Corrosion of silver: Silver corrosion is recognized by the formation of a black coating on the surface of silver articles when exposed to air, which is due to the formation of silver sulphide ( $\text{Ag}_2\text{S}$ ).

(d) Why iron corrosion is a serious problem: Iron is the most widely used structural metal in bridges, ships, railway tracks, automobiles, and buildings. Rusting continuously eats away and structurally weakens these iron objects, leading to catastrophic structural failures and costing billions of dollars annually in damage and replacement.

(e) Prevention of corrosion: Corrosion can be prevented by isolating the metal surface from air and moisture using the following methods:

Painting, oiling, or greasing the surface.
Galvanisation (coating iron or steel with a thin protective layer of zinc).
Anodising (forming a thick, protective oxide layer on metals like aluminium).
Alloying (mixing the metal with other metals or non-metals to change its properties).

corrosionrustingblack coatingsilver sulphidestructural weaknessgalvanisationanodisingalloying

Marking Scheme

1Define corrosion accurately as the degradation of metal by air, moisture, or chemicals. (1 mark)
2Identify the corrosion of iron as 'rusting'. (1 mark)
3State that silver turns black due to the formation of a silver sulphide layer. (1 mark)
4Explain the structural and economic damage caused by the rusting of iron. (1 mark)
5List at least two valid prevention methods (e.g., galvanisation, painting, anodising, alloying). (1 mark)

Hint

Recall the specific terms for iron corrosion, the color change of silver in air, and standard industrial methods used to protect iron structures.

Quick Oral Answer

Corrosion is the slow eating up of metals by atmospheric air and moisture. For iron, it is called rusting. Silver turns black due to silver sulphide. We can prevent it by painting, galvanising, or anodising.

Analysis & Explanation

This question covers the complete conceptual framework of corrosion as per the Class 10 syllabus:

Definition: Focuses on the chemical interaction of metals with environmental factors.
Iron & Silver: Highlights specific real-world examples of corrosion (rusting of iron and blackening of silver).
Socio-economic impact: Explains why iron corrosion is a major engineering and economic challenge.
Prevention: Lists practical methods to protect metals, emphasizing barrier protection (painting/greasing), sacrificial protection (galvanisation), and surface modification (anodising/alloying).

Common Mistakes

1Confusing the black coating of silver with copper's green coating.
2Using the term 'rusting' for metals other than iron.

Interesting Facts

Anodising is widely used on aluminium consumer electronics (like smartphones) to create a durable, corrosion-resistant, and beautifully dyed outer shell.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2014?

This question carries 5 marks in the CBSE Class 10 Science 2014 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Corrosion" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2014 paper?

This is a Long Answer question from Section SECTION-A in the CBSE Class 10 Science 2014 paper.