2.5.4Inorganic Chemistry
Alloys — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions
5 min read 5 parts Lesson 19 of 23 Unit quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Section 1 of 5What Is an Alloy?
Pure metals are often too soft for many uses, so they are combined with other elements.
Definition
- Definition An alloy is a mixture of a metal with one or more other elements, which may be metals or non-metals such as carbon.
Steel
- Steel Steel is an alloy of iron with a small amount of carbon.
Brass
- Brass Brass is an alloy of about 70% copper and 30% zinc.
Why make alloys
- Why make alloys Alloying changes the properties, often producing a material that is harder, stronger or more resistant to corrosion.
Section 2 of 5Structure of Pure Metals and Alloys
Structure of Pure Metals and Alloys
Pure metal
- Pure metal The atoms are all the same size and are arranged in regular layers.
Sliding layers
- Sliding layers Because the layers are regular, they slide over each other easily when a force is applied, so a pure metal is soft and malleable.
Alloy
- Alloy The added atoms are a different size, which distorts the regular layers.
Harder material
- Harder material The distorted layers cannot slide easily, so a larger force is needed to change the shape, making the alloy harder.
| Feature | Pure metal | Alloy |
|---|---|---|
| Atom sizes | All the same | Different sizes |
| Layers | Regular | Distorted |
| Hardness | Softer | Harder |
Section 3 of 5Examples of Steels
Examples of Steels
Mild steel
- Mild steel Mild steel has a low carbon content and stays soft and malleable, so it is used for car panels.
High carbon steel
- High carbon steel A higher carbon content makes it hard but more brittle, suited to tools like chisels.
Stainless steel
- Stainless steel Adding chromium and nickel gives a strong steel that resists corrosion, used for cutlery and sinks.
Comparison with iron
- Comparison with iron Pure iron is too soft for most uses, so steels are used instead.
Section 4 of 5Answering Exam Questions on Alloys
1
Draw or describe the regular layers of identical atoms in the pure metal.
2
State that the alloy contains atoms of different sizes.
3
Explain that the different atoms disrupt the regular arrangement of layers.
4
Conclude that the layers cannot slide as easily, so the alloy is harder than the pure metal.
Section 5 of 5Exam Checklist & Tips
2.5.4 – Key Points for the Exam
- Alloy A mixture of a metal with at least one other element.
- Lattice A regular three-dimensional arrangement of particles.
- Steel An alloy of iron and carbon.
- Brass An alloy of copper and zinc.
Common Mistakes
- Calling an alloy a compound; it is a mixture and the elements are not chemically bonded in fixed ratios.
- Saying alloys are harder because the atoms are stronger rather than because the layers cannot slide.
- Drawing alloy particles all the same size.
- Forgetting that an alloy can contain a non-metal such as carbon.
Last updated:
\n