Properties Uses And Alloys Of Metals

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Notes

Physical Properties of Metals

**Metals** conduct heat and electricity due to **delocalised electrons** that move through the structure.
They are **malleable** (can be hammered into shapes) and **ductile** (can be drawn into wires) because layers of positive ions can slide over each other.
Metals generally have **high melting and boiling points** because of strong electrostatic attraction (metallic bonds) between positive ions and delocalised electrons.

Chemical Properties of Metals

Metals react with **water** (cold or steam) to produce a metal hydroxide or oxide plus hydrogen gas.
Example with cold water: Ca + 2H₂O → Ca(OH)₂ + H₂.
Example with steam: Zn + H₂O → ZnO + H₂.
Metals react with **acids** to produce a salt and hydrogen: metal + acid → salt + hydrogen.
Example: $Fe + 2HCl$ → FeCl₂ + H₂.

Uses of Aluminium

Aluminium has **low density** and is **resistant to corrosion** due to a protective oxide layer.
Used in **aeroplane bodies** because of high strength-to-weight ratio.
Used in **overhead power cables** because it is a good electrical conductor and has low density.
Used in **food cans** because it is non-toxic and resistant to corrosion and acidic foods.

Uses of Copper

Copper is a **very good electrical conductor** and is **ductile**.
Used in **electrical wiring** due to high conductivity and ductility.
Used in **pots and pans** because it is a good heat conductor, unreactive, and malleable.
Used in **water pipes** because it is non-toxic, unreactive with water, and malleable.

Alloys – Composition and Properties

An **alloy** is a mixture of a metal with other elements (often other metals, sometimes non-metals).
**Brass** $(copper + zinc)$ is much stronger than either metal; used in musical instruments, ornaments, door knobs.
**Stainless steel** (iron + chromium, nickel, carbon) is hard and resistant to corrosion/rusting; used in cutlery.
Other alloys: iron with tungsten (extremely hard, heat resistant); aluminium with copper, manganese, silicon (strong, low density for aircraft).
Alloys are **not compounds** – they are mixtures, not chemically combined.

Structure of Alloys (Extended Tier)

Pure metals have a **regular arrangement** of positive ions in layers.
Alloys contain atoms of **different sizes**, which **distort** the regular lattice.
The distortion makes it **harder for layers to slide** over each other, so alloys are usually **harder/stronger** than pure metals.

Particle arrangement in solids, liquids, and gases – metals are solid at room temperature with a regular lattice.

Practice questions

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1.State two physical properties of metals.
Easy
2.State two uses of aluminium.
Easy
3.State two uses of copper.
Easy
4.What is an alloy?
Medium
5.State two examples of alloys and their uses.
Medium
6.Explain why alloys are usually harder than pure metals.
Hard
7.Which property makes aluminium suitable for making aeroplane bodies?
Easy
- Ahigh density
- Blow density
- Chigh reactivity
- Dpoor conductor of electricity
8.Which of the following is an alloy?
Medium
- Apure copper
- Bpure iron
- Cbrass
- Daluminium

Slides

Properties of Metals

Metals conduct heat and electricity because they have delocalised electrons that can move through the structure.
Metals are malleable (can be hammered into shapes) and ductile (can be drawn into wires) because layers of positive ions can slide over each other.
Metals usually have high melting and boiling points due to strong metallic bonds between positive ions and delocalised electrons.

Why can metals be drawn into wires?

Because they have delocalised electrons
Because layers of ions can slide over each other
Because they have high melting points
Because they are reactive

Uses of Aluminium

Aluminium is a reactive metal but is resistant to corrosion due to a thin protective layer of aluminium oxide.
It has a low density and a high strength-to-weight ratio.
Uses: aeroplane bodies (low density, strong), overhead power cables (good conductor, low density), food cans (non-toxic, resistant to corrosion).

Which of these are true about aluminium?

Aluminium is used in aeroplane bodies because it has a low density.
Aluminium reacts with water to form hydrogen gas.
Aluminium is a poor conductor of electricity.

Uses of Copper

Copper is an unreactive metal that is a very good conductor of electricity and heat.
It is ductile and malleable.
Uses: electrical wiring (good conductor, ductile), pots and pans (good conductor of heat, unreactive), water pipes (non-toxic, unreactive with water).

Which property makes copper suitable for electrical wiring?

Low density
High strength
Very good electrical conductor and ductile
Resistant to corrosion

What is an Alloy?

An alloy is a mixture of a metal with other elements (often other metals, but sometimes non-metals).
Alloys are not chemically combined; they are mixtures, not compounds.
Examples: brass (copper and zinc), stainless steel (iron with chromium, nickel, and carbon).

An alloy is $a ____ of a$ metal with other elements.

Properties of Alloys

Alloys often have enhanced properties compared to pure metals: they can be stronger, harder, and more resistant to corrosion or extreme temperatures.
The structure of an alloy is irregular: atoms of different sizes distort the regular metal lattice.
This distortion makes it harder for layers to slide, so alloys are usually harder and stronger than pure metals.

Why are alloys usually harder than pure metals?

They have a regular arrangement of atoms
They contain delocalised electrons
Different-sized atoms distort the layers, making it harder for them to slide
They have lower melting points

Examples of Alloys and Their Uses

Brass: alloy of copper and zinc; much stronger than either metal; used in musical instruments, ornaments, door knobs.
Stainless steel: alloy of iron with chromium, nickel, and carbon; hard and resistant to corrosion; used in cutlery.
Other alloys: iron with tungsten (extremely hard, heat resistant), aluminium with copper/manganese/silicon (strong but low density, used in aircraft).

Which of these are true about alloys?

Brass is an alloy of copper and zinc.
Stainless steel is an alloy of iron and carbon only.
Alloys are compounds.

Stainless steel is an alloy of iron with chromium, nickel, $and ____$ .

Summary of Metal Properties

Metals conduct electricity and heat, are malleable and ductile, and have high melting points.
Non-metals are usually brittle, do not conduct, and have low melting points (exceptions exist).
Alloys are mixtures with enhanced properties due to distorted atomic structure.

Which of the following is NOT a property of most metals?

Conduct electricity
Malleable
Brittle
High melting point

Flashcards

What are the general physical properties of metals?

Metals conduct heat and electricity, are malleable and ductile, and usually have high melting and boiling points.

Why do metals conduct heat and electricity?

Metals have delocalised electrons that are able to move through the metal structure.

Why are metals malleable and ductile?

The layers of positive metal ions in the metal structure are able to slide over each other.

Why do metals have high melting and boiling points?

There is a strong electrostatic attraction between positive metal ions and delocalised electrons (metallic bond), which requires lots of energy to break.

What are the general physical properties of non-metals?

Non-metals do not conduct heat and electricity (except graphite), are brittle, not malleable or ductile, and have low melting and boiling points.

What is the chemical property of metals when reacting with water?

Metals that react with cold water form a metal hydroxide and hydrogen gas. Metals that react with steam form a metal oxide and hydrogen gas.

What is the general equation for a metal reacting with an acid?

metal + acid → salt + hydrogen

Why is aluminium used in aeroplane bodies?

Aluminium has a high strength-to-weight ratio and low density.

Why is aluminium used in overhead power cables?

Aluminium is a good electrical conductor and has low density.

Why is aluminium used in food cans?

Aluminium is non-toxic and resistant to corrosion and acidic foods.

Why is copper used in electrical wiring?

Copper is a very good conductor of electricity and is ductile.

Why is copper used in pots and pans?

Copper is a very good conductor of heat, unreactive, and malleable.

Why is copper used in water pipes?

Copper is non-toxic, unreactive (does not react with water), and malleable.

What is an alloy?

An alloy is a mixture of a metal with other elements. Most alloys contain more than one metal; some contain non-metals.

What is brass and what are its uses?

Brass is an alloy of copper and zinc, much stronger than either metal. It is used in musical instruments, ornaments, and door knobs.

What is stainless steel and what is it used for?

Stainless steel is an alloy of iron with chromium, nickel, and carbon. It is used in cutlery because of its hardness and resistance to corrosion/rusting.

What are the properties of alloys compared to pure metals?

Alloys are often stronger, harder, and more resistant to corrosion or extreme temperatures than pure metals.

How does the structure of an alloy differ from a pure metal?

Pure metals have a regular arrangement of ions; alloys have an irregular arrangement of atoms due to different-sized atoms distorting the regular lattice.

Why are alloys usually harder/stronger than pure metals? (Extended tier)

The different-sized atoms in an alloy distort the regular layers, making it more difficult for the layers to slide over each other.

Is an alloy a compound or a mixture?

An alloy is a mixture, not a compound, because the elements are not chemically combined.

What is the reaction of calcium with cold water?

Ca $(s) + 2H2O (l)$ → $Ca(OH)2 (aq) + H2 (g)$

What is the reaction of zinc with steam?

Zn $(s) + H2O (g)$ → ZnO $(s) + H2 (g)$

What is the reaction of iron with hydrochloric acid?

Fe $(s) + 2HCl (aq)$ → $FeCl2 (aq) + H2 (g)$

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