# Physical properties of iron

> Why pure iron is not used, and its alloys are


## Objectives

- List the physical properties of pure iron given in the book.
- Explain why pure iron has no industrial importance and why steels and iron alloys are used.

## 1. Properties of iron




## 2. Iron everywhere, pure iron nowhere

Predict: why is pure iron not used to build things?

- It is not attracted by a magnet.
- It is relatively soft. ✓
- It is too hard to shape.
- It melts at a low temperature.

Pure iron is relatively soft, with low hardness, so it is not used to build things. It is magnetic, melts at 1538 °C, and is malleable and ductile, so those are not the reason.

[ar-EG] الـ iron النقي relatively soft وصلادته قليلة، عشان كده مش بيُستخدم في البناء. هو magnetic، وبينصهر عند 1538 °C، و malleable و ductile، يعني دي مش السبب.
## 3. Soft, malleable, ductile, magnetic

The book describes pure iron like this: Physical properties of pure iron (book p.20) Easy to shape is good for making things. Easy to dent is bad for a bridge.


## 4. Melting point and density

Melting point Density Density = mass ÷ volume. So every 1 cm³ of pure iron has a mass of 7.87 g. Volume of pure iron Mass


## 5. Purity decides the properties

Its physical properties depend upon its purity and the nature of its impurities. Impurities Other elements mixed with the iron, in small amounts. Pure iron: layers slip Steel: carbon blocks the slip Pure iron is very hard.


## 6. Many irons for many jobs

Pure iron is the most useful form of iron. A large number of steels and other iron alloys are made with specific properties suitable for many uses. Match each everyday use to the property of iron it relies on.


## 7. Your turn

A factory sample of iron is much harder than pure iron. Which is the best explanation?

- It is purer than normal iron.
- It has lost its magnetic properties.
- It contains other elements that block the slipping of its layers. ✓
- It has a lower melting point.

The factory iron is harder because it contains other elements: the physical properties of iron depend on its purity and the nature of its impurities, and these elements block the slipping of its layers. Pure iron itself is relatively soft.

[ar-EG] الـ iron اللي من المصنع أصلب عشان فيه عناصر تانية: الخواص الفيزيائية للـ iron بتعتمد على درجة نقاوته ونوع الشوائب اللي فيه، والعناصر دي بتمنع طبقاته إنها تتزحلق. أما الـ iron النقي نفسه فهو relatively soft.
## 8. Summary

Pure iron is relatively soft (low hardness), malleable, ductile and magnetic. It melts at 1538 °C. Its density is 7.87 g/cm³. Its physical properties depend on its purity and the nature of its impurities. So steels and iron alloys, not pure iron, are used in industry. Give reason: pure iron has no industrial importance. Key words: it is relatively soft, with low hardness. Back to the hook: can you explain why bridges are built from steel, not pure iron? Pure iron is relatively soft: its layers of atoms slip easily, so it dents easily. In steel, small carbon atoms block the slipping, so steel is harder.



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-fe.physical-properties