Unit 12
Materials and water.
Bonding and solutions at work: strength from weak ingredients, choosing a metal by a tensile test, and fresh water from the sea.
Before this unit
The unit, lesson by lesson
Lessons
3 lessons · 15 practice questions · about an hour
Natural materials
How wood is stronger than steel per kilogram though it is made of sugar: strength along the grain, levels within levels, nacre that stops cracks, and strength for weight.
Engineered materials
A tensile test on steel, aluminium, carbon fibre and a shape-memory alloy: Hooke's law, yielding and the stretch that stays, a brittle but strong material, specific strength, and an alloy that springs back.
Desalination
Why it takes so much pressure to make seawater drinkable: osmosis, osmotic pressure, reverse osmosis and the brine that pushes back, and a membrane that lets water through and stops ions.