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

Summary

Highlights

• Metal atoms have room for more electrons, allowing them to bond with up to 12 others 🧲.
• Metals are good conductors due to easily movable electrons 🔌.
• Early alloys like bronze were significant in ancient tool-making 🔨.
• Each alloy has unique applications, like brass in musical instruments 🎶.
• Alloys' hardness is due to disrupted atomic movement in the lattice ⛓️.

Key Takeaways

• Alloys retain metallic properties but are generally stronger 💪.
• Metal atoms can share electrons, making them good conductors ⚡.
• The history of alloys dates back to the Bronze Age 🕰️.
• Alloys like bronze and brass have specific practical applications 🎺.
• Alloys are harder to bend due to blocked atomic dislocation 🚫.

Overview

Chapters

• 00:00 - 00:30: Introduction to Alloys The chapter 'Introduction to Alloys' discusses how metals bond together to form alloys. Alloys retain the metallic characteristics of their component metals but tend to be stronger. It also touches on the nature of metal atoms, which typically have only a few electrons in their outer shells.
• 00:30 - 01:00: Metallic Bonding and Properties The chapter titled 'Metallic Bonding and Properties' discusses the nature of metallic bonding, highlighting that metal atoms have room in their valence shell to accommodate more electrons. As a result, each metal atom can bond with up to 12 others in a closely packed lattice. The chapter uses the example of a red atom surrounded by six atoms in its plane, three on top, and three underneath to illustrate this arrangement. It also mentions that less compact crystal structures, such as those where each atom is bonded to eight others, are possible due to the incomplete outer shells, which means there are still not enough electrons to complete the valence shell.
• 01:00 - 01:30: Conductivity and Ductility of Metals Metals exhibit excellent electrical and thermal conductivity due to the ease with which electrons move from one atom to another. This free movement is also responsible for their ductility. The non-localized nature of electron bonds allows metal atoms to slide past each other, thereby enabling them to change shape without breaking. When metals interact, they form metallic bonds, mixing into a lattice structure with no fixed proportions and random distribution, although the term for these structures was not provided in the transcript.
• 01:30 - 02:00: Formation and Characteristics of Alloys Alloys differ from compounds formed between metals and non-metals or purely non-metallic elements as their elemental proportions are not fixed. An example of an early alloy is bronze, which succeeded copper about 6,000 years ago in Europe during the late Stone Age. Initially, axes were made of pure copper, which proved too soft. By incorporating tin to create bronze, the resultant axes were much stronger.
• 02:00 - 02:30: Historical Context of Bronze In the chapter 'Historical Context of Bronze,' the arrival of the Bronze Age is discussed alongside the unique atomic structure of metals. It is explained that in metals, atoms are held together by non-directional bonds within a 'sea of loose electrons,' allowing the atoms to slide past one another while maintaining contact. This characteristic makes metals relatively easy to melt and bend but difficult to vaporize. Notably, when metals change shape, the process involves atoms slipping over one another incrementally, akin to shifting a carpet by moving it bit by bit.
• 02:30 - 03:00: Nature of Metallic Lattice and Movement The chapter 'Nature of Metallic Lattice and Movement' discusses the mechanics of atom movement within a metallic lattice. It highlights how atoms in a metal lattice can move easily one at a time, especially where there is a dislocation, making pure metals generally soft. The introduction of smaller or bigger atoms into the lattice blocks this easy movement of dislocations, thus stabilizing the structure.
• 03:00 - 03:30: Role of Atoms in Alloy Strength Atoms play a crucial role in the strength of alloys by affecting dislocations within the material's structure. When a dislocation encounters an obstacle, such as different atomic sizes or compositions, it requires greater force to move or continue bending the alloy. This increased resistance contributes to the overall strength and hardness of the alloy. The chapter also examines various well-known alloys, including bronze, brass, and carbon steel, detailing their compositions and typical uses. Bronze, composed of 3/4 copper and 1/4 tin, is used in sculptures and hardware. Brass, with 70% copper and 30% zinc, is common in musical instruments and door knockers. Carbon steel, mainly composed of 99% iron and up to 1% carbon, is widely used in building construction.
• 03:30 - 04:00: Examples of Different Alloys The chapter details various examples of alloys and their uses. It highlights the applications of different alloys in various fields such as vehicles, machinery, and everyday items. Examples include stainless steel, which is iron mixed with about 18% chromium and 8% nickel, commonly used for tableware, cookware, and surgical tools. Aluminum alloys used in planes often contain small percentages of copper or other metals. Amalgam, a mix of mercury with silver and other metals, was historically used in dental fillings. Solder, which consists of lead and tin, is used for joining electrical components.
• 04:00 - 04:30: Properties and Uses of Common Alloys The chapter discusses the properties and uses of common alloys. It highlights that gold, often used in wires and components, is typically alloyed with other metals like silver to increase its hardness. The purity of gold in an alloy is measured in carats, denoting how many parts of pure gold are present out of 24 parts of the alloy.

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

• 00:00 - 00:30 [Music] in this video we see how different Metals bond together to form Alloys which still retain the metallic properties of the starting Metals but are usually stronger metal atoms are typified by having only a few electrons in their outer shells
• 00:30 - 01:00 this means that even when they bond there's always room in this veence shell for more electrons each metal atom can bond with up to 12 others in a close packed latice look at the red atom it is surrounded by six in its plane and three on top and three underneath the less compact Crystal structures are possible too for example this Arrangement where each atom is bonded to eight others because there are still not enough electrons to complete the outer shell of
• 01:00 - 01:30 any of the atoms the electrons can move easily from one atom to another making metals good conductors of both electricity and heat and because the electrons are not localized in fixed bonds the atoms can slide past each other making them ductile allowing the metal to change shape it also means that when you try to react Metals together the atoms normally just mix into the lattice forming metallic bonds with each other and with no fixed proportions and randomly distributed these structures are called
• 01:30 - 02:00 Alloys contrast this with compounds between metals and non-metals or between non-metallic elements where the proportions of each element is fixed the oldest example of an alloy perhaps is the way bronze took over from copper in the early human communities of Europe around 6,000 years ago during the late Stone Age axes began to be made of pure copper but they were fairly soft when small amounts of tin were added to make bronze you got an axe which was was
• 02:00 - 02:30 twice as hard and worked well the Bronze Age had arrived the atoms in a metal latice are held by non-directional bonds a sort of sea of loose electrons as we said allowing the atoms to slide past each other still touching making Metals relatively easy to melt and bend but hard to vaporize when metals change shape atoms actually slip over each other like this however this process does not happen all at once but bit by bit rather like trying to move a carpet by putting
• 02:30 - 03:00 a Ruck in it here is the way it happens in a metal you see the slip moving easily one atom at a time where there's a dislocation in the latice it is this easy movement of atoms in the crystal latice that makes most pure Metals soft now put a smaller or bigger atom into the latice and this easy movement of the dislocation is blocked see the way the bigger atoms stabilizes the
• 03:00 - 03:30 dislocation which gets no further unless you put greater force meaning that it's harder to bend the alloy to finish let's look at some well-known Alloys bronze 3/4 copper quarter tin for sculptures boat Hardware screws and Grill work brass 70% copper 30% zinc musical instruments coins door knockers carbon steel 99% iron and up to 1 % carbon for building construction
• 03:30 - 04:00 tools car bodies Machinery rails Etc stainless steel iron with about 18% chromium and 8% nickel used for table wear cookware surgical tools and so on aluminium Alloys for planes contain a few percent of copper or other metals amalgam is mercury with silver and other metals once used for dental fillings solder lead and Tin for join electrical
• 04:00 - 04:30 wires and components melts very easily gold is usually an alloy containing another metal such as silver for increasing hardness the number of carrots K defines how many mass parts of pure gold are found in 24 parts of the alloy for