Alloy & their Properties | Properties of Matter | Chemistry | FuseSchool

Summary

This video explains how metals bond to form alloys, which retain the metallic properties of their base metals but often provide enhanced strength. It covers the atomic structure of metals, how they form alloys, and how these alloys differ from compounds. The video also explores the properties of metals, such as electrical and heat conductivity, ductility, and the ease of atoms moving past one another. Common alloys like bronze, brass, carbon steel, and stainless steel are introduced, along with their uses in everyday items like tools, coins, and medical instruments. The role of different metals in these alloys is also highlighted.

Takeaways

• 😀 Metals bond together to form alloys, which retain metallic properties but are usually stronger.
• 😀 Metal atoms have a few electrons in their outer shells, making them capable of bonding with other atoms in a lattice structure.
• 😀 In alloys, metal atoms bond in close-packed lattices, allowing them to bond with up to 12 other atoms.
• 😀 Alloys can have less compact crystal structures, where atoms bond with fewer atoms, such as eight.
• 😀 Electrons in metal atoms are free to move easily between atoms, making metals good conductors of heat and electricity.
• 😀 The non-localized electrons in metals allow atoms to slide past each other, making them ductile and capable of changing shape.
• 😀 In alloys, the metal atoms mix randomly without fixed proportions, forming metallic bonds.
• 😀 Alloys differ from compounds, which have fixed proportions of elements, typically involving metals and non-metals.
• 😀 An example of an early alloy is bronze, made by adding tin to copper to create stronger, harder axes in the Bronze Age.
• 😀 The non-directional bonds in metal lattices allow atoms to slip past each other, making metals relatively easy to bend but hard to vaporize.
• 😀 Adding different-sized atoms to a metal lattice can block the easy movement of atoms, making the alloy harder to bend and stronger.
• 😀 Common alloys include bronze (copper and tin), brass (copper and zinc), carbon steel (iron and carbon), stainless steel (iron, chromium, and nickel), and aluminum alloys (with copper and other metals).

Q & A

What is an alloy?

An alloy is a mixture of metals, where the atoms bond in a lattice structure, retaining metallic properties but with different physical characteristics compared to pure metals.

Why are metals good conductors of electricity and heat?

Metals are good conductors because their electrons are not fixed in bonds and can move easily from one atom to another, allowing the transfer of electricity and heat.

How does the arrangement of atoms in a metal affect its properties?

The arrangement of atoms in a metal is typically a close-packed lattice, which allows the atoms to slide past each other, making metals ductile and able to change shape under stress.

What is the difference between alloys and compounds?

Alloys are mixtures of metals, where the proportions and distribution of elements are random, while compounds have fixed proportions of elements and distinct chemical bonds.

What is the historical significance of bronze as an alloy?

Bronze, made by adding tin to copper, was crucial during the Bronze Age as it replaced copper for making tools, offering a much harder material for tasks like crafting axes.

What role do dislocations play in the behavior of metals?

Dislocations in a metal's crystal lattice allow atoms to move past each other, making the metal malleable and ductile. This movement is what enables metals to bend and change shape.

How do alloying elements like larger or smaller atoms affect the metal's strength?

Larger or smaller atoms inserted into the metal lattice can block the easy movement of dislocations, making the alloy harder to bend and increasing its strength.

What are some common alloys and their uses?

Examples include bronze (used for sculptures and hardware), brass (musical instruments, coins), carbon steel (construction, tools), stainless steel (surgical tools, cookware), and aluminum alloys (aircrafts).

How is gold typically alloyed, and why is this done?

Gold is often alloyed with other metals like silver to increase hardness. The purity of gold in an alloy is measured in carats, with 24 carats being pure gold.

What makes metals relatively easy to melt and bend, but hard to vaporize?

The non-directional bonds between metal atoms, forming a 'sea' of electrons, make metals easy to bend and melt, but the strong bonds prevent them from vaporizing easily.