Mechanism of heating and cooling

• Conduction is the transfer of heat between adjacent bodies or materials in direct contact.
• Metals are good conductors because they have free electrons that can move around easily, allowing them to carry thermal energy quickly from one atom to another.
• Thermal conductivity is a measure of how well a material transfers heat by conduction.
• The rate at which heat flows by conduction depends on the temperature difference across two objects and their relative areas exposed to each other.
• The higher the thermal conductivity, the better the material is at conducting heat.
• A vacuum has zero thermal conductivity since there are no particles present to transmit heat.
• Convection: the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat
• Thermal energy is the total energy of all particles in an object
• Temperature is the measurement of the average kinetic energy of the particles in a substance.
• The three pillars of sustainability are: Economic, Social resources and Environmental.
• The definition of sustainability is the ability to meet the needs of the present without compromising the ability of future generations to meet their own needs.
• Carbohydrates, fats and proteins are the main macronutrients
• Radiation is the transfer of energy in the form of electromagnetic waves, such as light and radio waves
• Conductors and insulators are materials that allow or prevent the flow of electricity.
• When an object is heated, energy is transferred to its thermal energy store
• Heating can take place in three different ways depending on the medium involved:

  • Conduction for solids
  • Convection for fluids
  • Radiation through empty space
• Conduction:

  • Vibrating particles transfer energy to neighboring particles
  • Particles vibrate faster and collide with more energy, passing along the energy until heat is spread out evenly
  • Mainly occurs in solids due to closely held particles
  • Thermal conductivity determines how well objects transfer energy by conduction
• Convection:

  • Mainly occurs in fluids (liquids and gases)
  • Particles in fluids move around faster by random diffusion when heated
  • Higher energy particles move away from the warmer region towards the cooler region, causing fluid expansion and less density in the warmer region
  • Forms convection currents
  • Seen in oceans, inside buildings with radiators
  • Reduced by stopping the free flow of fluids, like sleeping under a blanket
• Conduction and convection both involve particles gaining kinetic energy

  • In conduction, energy is transferred between particles
  • In convection, particles themselves move
• Radiation:

  • Heat energy can be transferred without particles
  • Energy is carried by infrared waves
  • Objects constantly absorb and emit radiation
  • Hotter objects emit more radiation
  • Infrared radiation is absorbed by objects, making them feel hot
  • Infrared radiation is emitted by very hot objects like metal and coal