Aluminium is used in thermite welding because it:A.) Is a light metalB.) Has more affinity for oxygenC.) Is a strong oxidising agentD.) Is a reactive metal

To solve the question about why aluminum is used in thermite welding, let's break down each option:

Thermite Welding
Thermite welding is a process that involves a chemical reaction between aluminum powder and a metal oxide (typically iron oxide). The reaction is highly exothermic, meaning it releases a large amount of heat, which melts the metals involved and allows them to fuse together.

Options Analysis
A) Is a light metal

While aluminum is indeed a light metal, this property is not directly related to its role in thermite welding. The primary function of aluminum in this process is related to its chemical reactivity rather than its weight.
B) Has more affinity for oxygen

Aluminum has a high affinity for oxygen, which means it readily reacts with oxygen to form aluminum oxide. In the thermite reaction, aluminum reduces the iron oxide (Fe₂O₃) to produce iron and aluminum oxide. This high affinity for oxygen makes aluminum an effective reducing agent in the reaction.
C) Is a strong oxidizing agent

This is incorrect. Aluminum is not an oxidizing agent; it is a reducing agent. An oxidizing agent accepts electrons, while a reducing agent donates electrons. In the thermite reaction, aluminum donates electrons to reduce iron oxide.
D) Is a reactive metal

This is partially true. Aluminum is a reactive metal, meaning it reacts readily with other substances. However, the specific reason aluminum is used in thermite welding is due to its ability to reduce metal oxides because of its high affinity for oxygen.
Conclusion
The correct answer is B) Has more affinity for oxygen. Aluminum's high affinity for oxygen allows it to effectively reduce iron oxide in the thermite reaction, producing the intense heat necessary for welding.