Understanding Heat Conduction

Ever wondered why metal spoons get hot in your tea but plastic ones don't? It's all about thermal conductors - materials that let heat move through them easily. Metals are brilliant at this because of their free electrons that carry energy around.

The speed at which heat moves depends on three key factors: how big the temperature difference is, how thick the material is, and what it's actually made of. Think of it like water flowing through a pipe - the bigger the pressure difference and the wider the pipe, the faster it flows.

Insulation works by doing the opposite - it reduces energy transfer to keep heat where you want it. This is why people spend money on home insulation - it literally saves them cash on heating bills by keeping warm air inside where it belongs.

Quick Tip: In your practical experiment, you'll measure how temperature changes over time by timing cooling water every 2 minutes for 20 minutes.

Keeping Homes Warm and Heat Loss Prevention

Your home is constantly losing heat through five main escape routes, but there are clever ways to block each one. Double glazing traps air between glass panes because air is rubbish at conducting heat. Loft insulation stops warm air from sneaking out through your roof.

Cavity wall insulation involves pumping special material into the gap between your walls. This stops heat escaping and prevents convection currents from forming. Even simple things like carpets and draught excluders make a real difference to your energy bills.

Infrared radiation is the invisible electromagnetic wave that carries heat energy - you can actually feel it on your skin when you're near something warm. All objects give off this radiation, and the hotter they are, the more they emit.

A perfect black body absorbs every bit of radiation that hits it, making it also the best possible emitter. This is why dark, matt surfaces heat up faster than shiny, light-coloured ones.

Real World Connection: Earth's temperature depends entirely on balancing the infrared radiation we absorb from the sun with what we emit back to space.

Measuring Heat and Specific Heat Capacity

The Leslie cube practical shows you how different surfaces emit infrared radiation at different rates. You'll fill it with boiling water, let the surfaces heat up for a minute, then use an infrared detector to measure emission intensity from each surface at the same distance.

Specific heat capacity tells you how much energy you need to heat up 1kg of something by 1°C. It's like asking "how stubborn is this material about getting warmer?" The formula is straightforward: Energy = mass × specific heat capacity × temperature change.

Materials with high specific heat capacity need loads of energy to warm up (like water), whilst others heat up quickly with just a little energy (like metals). This explains why water takes ages to boil but a metal pan heats up almost instantly.

In the required practical, you'll heat an aluminium block with an electrical heater, measuring voltage and current every minute for 10 minutes. Even after switching off, the temperature keeps rising for a bit - this is normal and shows heat is still spreading through the block.

Exam Success: Remember that specific heat capacity can be rearranged - you might need to find heat capacity = energy ÷ (mass × temperature change).