Links between physics and chemistry in everyday contexts
Links between physics and chemistry in everyday contexts tests your ability to choose and explain materials, devices and processes using both physical and chemical ideas.
Core links
- Materials selection depends on properties: thermal conductivity, electrical conductivity, strength, density, malleability, resistance to corrosion.
- Chemical reactions transfer energy: exothermic releases, endothermic absorbs. Batteries convert chemical energy to electrical energy; electrolysis uses electrical energy to drive chemical change.
- Corrosion is a chemical reaction; rusting needs oxygen and water. Sacrificial protection uses a more reactive metal.
- Polymers are long-chain molecules; properties depend on chain length and cross-linking. Composites combine materials for better properties.
- Cooking involves heat transfer and chemical changes such as denaturation; insulation reduces unwanted energy transfer.
Worked example
Choose materials for a saucepan. The base should be a metal such as aluminium because it has high thermal conductivity and is malleable, so heat transfers quickly from the hob to food. The handle should be a plastic or wood because it has low thermal conductivity, reducing heat transfer to the hand. If the handle also needs strength, a composite may be used. The choice links a physical property (conductivity) to a function (heating or insulating).
Traps
Assuming 'natural' always means better; confusing physical changes with chemical changes; saying a battery 'stores electricity' rather than chemical energy; ignoring corrosion conditions; choosing a material by cost alone without property reasons.