Problem 21 - A Complete Resource Book in Chemistry for JEE Main

Question

Iron loses its magnetic property at (a) melting point (b) curie point (c) \(1000 \mathrm{~K}\) (d) boiling point

Step-by-Step Solution

Answer

Iron loses its magnetic property at the Curie point.

Step 1: Understanding the Properties

Different points of temperature can affect the properties of materials, such as melting, boiling, and Curie point, which is specifically related to magnetism.

Step 2: Identifying Curie Point

The Curie point is a specific temperature where the magnetic properties of a material change. For iron, this temperature is about 770°C or 1043 K.

Step 3: Eliminating Other Options

Iron melts at about 1811 K and boils at 3134 K. Neither of these temperatures specifically affects the magnetic properties of iron as much as the Curie point does.

Step 4: Selecting the Correct Option

Knowing that the Curie point is the temperature where iron loses its magnetic properties, choose option (b) as the correct answer.

Key Concepts

Magnetic Properties

We often hear about materials exhibiting fascinating magnetic properties. Understanding these properties can help us comprehend why certain materials can attract or repel objects. Magnetic properties of a material are related to its atomic and molecular structure. This tells us how the electrons are arranged and whether they can align to produce a magnetic field.

There are several kinds of magnetism, including:

• Diamagnetism: This is a weak form of magnetism present in all materials. However, it's usually overshadowed by stronger effects like ferromagnetism.
• Paramagnetism: Here, materials are weakly attracted by external magnetic fields and do not retain the magnetic properties when the field is removed.
• Ferromagnetism: The most common type associated with permanent magnets. It is present in materials like iron, where internal magnetic alignment occurs without an external field.

In essence, these properties dictate how materials like iron behave in magnetic fields. Only ferromagnetic materials retain magnetism after an external magnetic force is removed. This fascinating phenomenon is crucial in various technological applications.

Iron

Iron is one of the most abundant metals on Earth and perhaps the most well-known for its magnetic properties. Its association with magnets is primarily due to its ferromagnetic nature. Let's dive a bit deeper into what makes iron magnetic.

Iron atoms have unpaired electrons in their outer shell, which allows them to align with one another when exposed to a magnetic field. In bulk iron, these aligned electrons create regions known as magnetic domains.

• When these domains are aligned in the same direction, the iron behaves like a magnet.
• However, if the domains are randomly oriented, iron does not exhibit noticeable magnetism.
• These properties make iron very useful in manufacturing magnets and various electronic devices.

Iron's ability to be magnetized and de-magnetized quickly gives it versatile applications in numerous fields, including electronics, construction, and telecommunication.

Temperature Effects

Temperature has a significant impact on the magnetic properties of materials, particularly with ferromagnetic substances like iron. One crucial temperature in this context is the Curie point.

The Curie point is the temperature at which a ferromagnetic material loses its permanent magnetism. For iron, this critical temperature is approximately 770°C (1043 K).

• Above the Curie point, iron's thermal energy disrupts the alignment of magnetic domains, causing it to lose its magnetic properties and become paramagnetic.
• When cooled back below this temperature, iron can regain its former ferromagnetic character, as the domains realign.

This understanding is vital in various fields, especially in designing and operating devices that rely on magnetic materials. Real-world applications include data storage solutions, transformers, and electromagnets, which need to maintain integrity without losing magnetic properties under varied temperature conditions.