P1.1 Heat Transfer

Particle Structure

Solids

• Tightly packed in a regular pattern
• Particles have low energy
• Their only movement is vibrating about their fixed positions

Liquids

• Particles are less tightly packed and can move around eachother
• As the particles move more they have more energy than the particles in the solid

Gas

• Particles are spread out with large spaces between them
• Particles can move in all directions
• So they have lots of energy

Conduction

Slow Method - All solids

• Particles which are heated gain energy
• This means they vibrate more
• They pass on increased vibrations to their neighbouring particles

Fast Method - Metals only

• Metals contain free electrons  which can move freely throughout the metal
• When the metal is heated the free electrons gain energy
• They pass the energy on by colliding with another particle

Convection

Convection is a heat transfer that occurs in fluids. A fluid can be a gas or a liquid.

Explanation

• The particles in the part of the fluid which is heated gain energy and they move around more/vibrate more
• This means they spread out and the warm fluid becomes less dense
• The warmer fluid rises and colder, more dense fluid takes its place
• This process repeats forming a convection current

Convection cannot occur in solids because the particles are fixed and unable to move past each other. 

Radiation

• Between the Earth and the Sun there is a vacuum
• In that vacuum there are no particles
• So heat transfer by Conduction or Convection is not possible
• Heat is instead transferred by radiation
• Radiation as an electromagnetic wave
• All objects give off (emit) radiation
• The hotter an object is the radiation it emits
• All objects take in (absorb) radiation

A dull, black surface is the best at absorbing radiation

A shiny, silver surface is the best at reflecting radiation

Evaporation and Condensation

Evaporation

Evaporation is a process of when a liquid turns into a gas/vapour

Factors affecting the rate of evaporation

• Increasing the surface area of the liquid
• Increasing the temperature of the liquid
• Creating a…