1.3 Conduction
|
|
A saucepan has a handle that is an insulator because we do not want the hand to be hot. The pan part will be made out a good conductor of heat because we want this part to be hot so that the food cooks.
Heat can be transferred from one place to another by conduction. Conduction occurs solids. Metals are good conductors of heat. Non-metals are usually poor conductors of heat and these are known as insulators. Examples of good insulators are wool or fibreglass.
Conduction of heat energy is where particles with more kinetic energy (hotter particles) pass on their extra kinetic energy to neighbouring particles by vibrating. If we have a piece of metal that is warm at one end and cold at the other, the particles at the warm end pass on some of their kinetic energy to their neighbouring particles who then pass on energy to their neighbouring particles and this will eventually warm up the particles at the other end of the piece of metal. An example of where this would take place, is the handle on a saucepan which is on a hob. The handle will get hot because plastic is a poor conductor.
Conduction of heat energy is where particles with more kinetic energy (hotter particles) pass on their extra kinetic energy to neighbouring particles by vibrating. If we have a piece of metal that is warm at one end and cold at the other, the particles at the warm end pass on some of their kinetic energy to their neighbouring particles who then pass on energy to their neighbouring particles and this will eventually warm up the particles at the other end of the piece of metal. An example of where this would take place, is the handle on a saucepan which is on a hob. The handle will get hot because plastic is a poor conductor.
Conduction is usually faster in denser solids because the particles are closer together, meaning that the kinetic energy passes on from one particle to another quicker. On the contrary, materials where particles are further apart, are poorer at conducting heat as the particles collide much less frequently.
Like I have said, metals are good conductors of heat. This is because electrons are able to leave their atoms and move about inside the metal. The electrons at the hot end of a piece of metal move faster and collide with other free electrons from other atoms, thus transferring energy. These electrons then pass on the energy to close by electrons. As the electrons can move freely, the transfer of kinetic energy (heat) is faster than if the electrons had to stay with their own atom, thus meaning that metals are very good conductors of heat.
Like I have said, metals are good conductors of heat. This is because electrons are able to leave their atoms and move about inside the metal. The electrons at the hot end of a piece of metal move faster and collide with other free electrons from other atoms, thus transferring energy. These electrons then pass on the energy to close by electrons. As the electrons can move freely, the transfer of kinetic energy (heat) is faster than if the electrons had to stay with their own atom, thus meaning that metals are very good conductors of heat.
An Example
Let’s suppose that we have a Bunsen burner that is placed underneath the left side of a piece of metal. When the Bunsen burner is switched off, all of the particles have the same amount of energy and they vibrate at the same rate.
When the Bunsen burner is switched on, the particles on the left start to warm up. This results in the particles having more energy causing them to vibrate more intensively around their fixed position. These particles pass energy onto their surrounding particles, who then start to vibrate more. This process continues resulting in the right side of the piece of metal becoming hot.
Let’s suppose that we have a Bunsen burner that is placed underneath the left side of a piece of metal. When the Bunsen burner is switched off, all of the particles have the same amount of energy and they vibrate at the same rate.
When the Bunsen burner is switched on, the particles on the left start to warm up. This results in the particles having more energy causing them to vibrate more intensively around their fixed position. These particles pass energy onto their surrounding particles, who then start to vibrate more. This process continues resulting in the right side of the piece of metal becoming hot.