All questions of Metals and Non-Metals for Class 10 Exam

Metallic properties refer to the characteristic features of metals. Metals are a group of elements that possess certain common properties such as electrical conduction, thermal conduction, malleability, ductility, and a lustrous appearance. However, one property that is generally not shown by metals is dullness.

Dullness refers to the lack of shine or luster in an object. In the context of metals, dullness implies that the surface of the metal does not reflect light and appears matte or non-reflective. This property is typically associated with non-metals or non-metallic substances.

Explanation:

- Reflectivity and Luster:
Metals are known for their characteristic luster or shine. When light falls on the surface of a metal, it gets reflected uniformly, resulting in a shiny appearance. This property is due to the presence of free electrons in the metal lattice, which allows for the easy movement of light waves. As a result, metals are excellent reflectors of light and have a high degree of luster.

- Electrical Conduction:
Metals are excellent conductors of electricity. This property is due to the presence of delocalized electrons in the metal lattice. These free electrons are not bound to any specific atom and can move freely within the metal structure. When a voltage is applied across a metal, these free electrons can easily move and carry the electric current.

- Sonorous Nature:
Metals also possess the property of being sonorous, which means they produce a ringing sound when struck. This property is again related to the presence of free electrons in the metal lattice. When a metal is struck, the force of the impact causes the metal atoms to vibrate. These vibrations are transmitted through the lattice, resulting in the production of sound waves.

- Ductility:
Ductility is the property of a material to be drawn into thin wires without breaking. Metals are highly ductile due to the presence of metallic bonds. Metallic bonds are formed by the sharing of valence electrons between atoms. This arrangement allows the atoms to slide over each other when a force is applied, making the metal malleable and ductile.

In conclusion, metals generally do not exhibit the property of dullness. They are highly reflective and possess a characteristic luster. Other properties exhibited by metals include electrical conduction, sonorous nature, and ductility.

Explanation:

When a more reactive metal displaces a less reactive metal from its salt solution, it is known as a displacement reaction. In this case, we need to determine which metal can displace the other three metals from their salt solutions.

To determine the reactivity of the metals, we can refer to the reactivity series of metals. The reactivity series is a list of metals arranged in order of their reactivity, with the most reactive metal at the top and the least reactive metal at the bottom.

The reactivity series of metals from most reactive to least reactive is as follows:
Potassium (K) - Sodium (Na) - Calcium (Ca) - Magnesium (Mg) - Aluminum (Al) - Zinc (Zn) - Iron (Fe) - Lead (Pb) - Hydrogen (H) - Copper (Cu) - Silver (Ag) - Gold (Au)

Analysis of the options:
a) Cu (Copper) - Copper is less reactive than silver, magnesium, and zinc. It cannot displace any of the other three metals from their salt solutions.

b) Ag (Silver) - Silver is less reactive than magnesium and zinc but more reactive than copper. It can displace copper from its salt solution but cannot displace magnesium or zinc.

c) Mg (Magnesium) - Magnesium is more reactive than copper, silver, and zinc. It can displace copper and silver from their salt solutions but cannot displace zinc.

d) Zn (Zinc) - Zinc is more reactive than copper, silver, and magnesium. It can displace copper, silver, and magnesium from their salt solutions.

Conclusion:
Based on the reactivity series, the metal that can be displaced from the solution of its salts by the other three metals is silver (Ag). Therefore, the correct answer is option b) Ag.

Introduction to Safety Fuse Wire
Safety fuse wires are crucial components in electrical circuits, designed to protect against overcurrent. Their primary function is to melt and break the circuit when excessive current flows, preventing potential hazards like electrical fires.
Material Composition of Fuse Wire
The correct answer is that safety fuse wire is made from an alloy of tin and lead. Here’s why:
Key Properties of Tin and Lead Alloy
- Low Melting Point:
- The alloy of tin and lead has a lower melting point compared to pure metals like copper or silver. This allows the fuse to melt quickly when the current exceeds safe levels.
- Good Conductivity:
- While not as conductive as copper or silver, the alloy still provides adequate conductivity for normal operating conditions.
- Cost-Effectiveness:
- Tin and lead alloys are less expensive than precious metals like platinum and silver, making them more practical for widespread use in fuse wires.
Why Not Other Metals?
- Platinum:
- Extremely expensive and has a high melting point, making it unsuitable for fuse applications.
- Silver:
- While highly conductive, silver is not cost-effective for fuse wires and has a higher melting point compared to the tin-lead alloy.
- Copper:
- Though conductive, copper does not melt as easily as the tin-lead alloy, making it less effective for fuse applications.
Conclusion
In summary, the safety fuse wire is made from an alloy of tin and lead due to its optimal melting point, adequate conductivity, and cost-effectiveness. This combination ensures reliable operation in protecting electrical circuits.

Reason for the Formation of Green Coating on Copper:

When copper is exposed to air, it slowly loses its shining brown surface and gains a green coating. This green coating is known as copper carbonate (CuCO3) or copper(II) carbonate hydroxide (Cu2CO3(OH)2), which is commonly known as verdigris. The formation of this green coating is primarily due to the reaction of copper with carbon dioxide and moisture present in the air.

Explanation:

1. Reaction with Carbon Dioxide:
- Copper reacts with carbon dioxide present in the air to form copper(II) oxide (CuO).
- The reaction can be represented as:
2Cu + O2 + CO2 → 2CuO + CO
- Copper(II) oxide is a black compound.

2. Reaction with Moisture:
- Copper(II) oxide further reacts with moisture present in the air to form copper(II) hydroxide (Cu(OH)2).
- The reaction can be represented as:
CuO + H2O → Cu(OH)2
- Copper(II) hydroxide is a blue compound.

3. Reaction with Carbon Dioxide and Moisture:
- Copper(II) hydroxide reacts with carbon dioxide present in the air to form copper carbonate (CuCO3).
- The reaction can be represented as:
Cu(OH)2 + CO2 → CuCO3 + H2O
- Copper carbonate is a green compound.

Conclusion:

The formation of the green coating on copper is due to the reaction of copper with carbon dioxide and moisture present in the air. Initially, copper reacts with carbon dioxide to form copper(II) oxide, which further reacts with moisture to form copper(II) hydroxide. Finally, copper(II) hydroxide reacts with carbon dioxide to form copper carbonate. This copper carbonate coating gives the characteristic green color to the surface of the copper.