How Heat Works: The Fundamental Physics of Cooking - Section 4: Material Properties and Heat Behavior

Different materials interact with heat in distinctive ways, and these properties significantly impact cooking outcomes. Understanding how various cooking vessels and foods respond to heat helps you make better equipment choices and adjust techniques appropriately.

Thermal conductivity measures how efficiently a material transfers heat. Metals generally have high thermal conductivity, which is why they're popular for cookware. Copper conducts heat extremely well, providing quick, responsive temperature changes—ideal for delicate sauces. Cast iron conducts heat more slowly but retains it exceptionally well, making it perfect for searing meats or maintaining steady temperatures. Glass and ceramic have low thermal conductivity, which is why they heat slowly and unevenly but help keep foods warm longer.

These properties explain why professional chefs are particular about their cookware choices for different tasks. When you need precise temperature control, materials with high conductivity shine. When you want consistent heat without fluctuations, materials with high heat capacity and retention work better.

Foods themselves also have varying thermal properties. Fats conduct heat poorly compared to water, but they can reach much higher temperatures. This explains why oil can get hot enough to brown food surfaces while water maxes out at its boiling point. Air trapped in foods like bread or cake acts as an insulator, slowing heat transfer to create gradual cooking from outside to inside.

Heat capacity—how much energy a material can store—also affects cooking. Water has a remarkably high heat capacity, requiring substantial energy to change its temperature. This is why adding room-temperature vegetables to boiling water barely reduces the water's temperature, but placing the same vegetables on a hot pan significantly cools the pan's surface.

The way materials expand and contract with temperature changes matters too. Metal expands when heated, which is why quality cookware often has layered construction to prevent warping. Foods undergo more dramatic changes—starches expand as they absorb water, proteins contract as they denature, and air pockets expand when heated, explaining how bread rises and soufflés puff up.