S4.6.8 For the adult
Metals and alloys
Why can a metal wire be bent, when a lump of salt shatters?
What this chapter teaches
In a metal, positive ions sit in layers in a sea of free electrons. The electrons carry charge and heat, and the layers can slide, so metals conduct and bend. In an alloy, atoms of other sizes disturb the layers, so the alloy is harder.
Three questions to ask
There is no one right wording. Listen for the idea.
- What is metallic bonding?
- Why can a metal be bent but a crystal of salt shatters?
- Why is brass harder than pure copper?
After the chapter, the learner can
- Explain how metallic bonding lets metals conduct and bend
- Explain why alloys are harder than pure metals
What they copy into their notebook
A metal is positive ions in a sea of free electrons. The electrons carry charge and heat. Layers slide, so metals bend. In an alloy, atoms of other sizes block the layers, so it is harder.