Thermal Processes - 8

Thermal energy always flows from a region of higher temperature to a region of lower temperature

It is when 2 regions or bodies have the same temperature hence there is no net flow of thermal energy between them

Conduction, Convection & Radiation

It is the transfer of thermal energy through a medium without the flow of a medium (meaning particles do not move from 1 place to another)

Solids, Liquids & Gases (not vacuum)

When 1 end of it is heated, particles at this end will gain kinetic energy and vibrate faster. These energetic particles collide with their neighbouring particles and transfer some of the kinetic energy to them causing them to vibrate faster too. Heat is therefore conducted from the hot end of the solid to the cold end through the collisions of particles

Particles in solids are closely packed while the particles in liquids are further apart and in gases, particles are far apart. The rate of collisions between in solids is more frequent hence the heat conducted from 1 end to another through collisions is faster in solids

They contain free electrons or mobile electrons. When heated, these electrons gain kinetic energy and move faster. They can travel quickly in the empty spaces between the particles, colliding with particles at the cooler part of the rod and transfer some of the kinetic energy to them. This is called free electron diffusion

frying pan/pot, copper bit of soldering iron, metal pipe in heater & metal base in iron

Handles of cooking utensils, table mats, styrofoam, woolen winter jackets & more

The birds can trap air between their feathers. Since air is a poor thermal conductor, this reduces heat loss from the bird’s body to the surrounding by conduction

It is the process by which heat is transmitted from 1 place to another by the movement of heated particles in a gas or liquid due to the difference in density.

There is no heat transfer as a solid’s particles are fixed in their positions

Mass (kg) / Volume (m^3)

When a part of a liquid is heated, the volume of that part will increase to due expansion. This causes the density to decrease. The hot, less dense liquid will rise and the cooler, denser liquid above will sink to take the place of the warmer liquid to be heated. This is called a convection current

When air is cooled, its volume decreases due to contraction. This causes it to become denser than the surrounding air. The cooler, denser air will sink while the warmer, less dense air will rise to take its place to be cooled. This is called a convection current

The ground and on the ceiling respectively

It is the transfer of thermal energy in the form of electromagnetic waves such as infrared radiation without the aid of a medium

Yes as it does not require particles for heat transfer

Color & texture, Surface Area & Surface Temperature

Surfaces that are dull and dark are good emitters and absorbers of radiation while shiny and bright ones are poor emitters and absorbers of radiation (good reflector)

A body of larger surface area will emit and absorb more infrared radiation to and from the surrounding

The hotter an object, the more infrared radiation is emitted to the surroundings

teapots & kettles as well as sunshades in cars

It is a good absorber of infrared radiation allowing the solar panel to absorb more energy to be converted to electrical energy