Conduction: Conduction in Liquids and Gases

Liquids and Gases are poor conductors of heat.

In liquids and gases, the atoms are spaced further apart as compared to solids, which will cause the collisions between the atoms to be lesser.

Liquids conduct thermal energy slower than solid, but faster than gases, as the atoms are spaced further apart when compared to solid but closer to each other when compared to liquid.

In liquids, it is the impurities (e.g. salt, dirt) that are conducting heat, not the water itself.
Thus, distilled water DO NOT conduct heat.

Gases conduct thermal energy the slowest among the 3 states as the atoms in gases is spaced furthest apart.

Gases are usually insulators of heat (poor conductors of heat).
e.g. Wool used as winter clothings.
It can trap pockets of air in it, reducing heat transfer by conduction.

Conduction: Conduction in Metals.

Metals are good conductors of thermal energy as the atoms of metals are very closely packed together so the vibrations are passed on very quickly and they also have a lot of free electrons. When the metal is being heated, the free electrons that are close to the heat source is also heated. As they are heated, they will move around the metal faster than usual, colliding into atoms and other electrons, which will make the others vibrate faster as well. That is why metals are good conductors of heat.
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Video
The following video shows that different metals conduct heat at different rates.

In the video,there are 5 rods that are of the same length attached to the handle. At the end of each rod, there is a flag attached to the rod with wax.

Flag #1 - Steel
Flag #2 - Brass
Flag #3 - Aluminum
Flag #4 - Stainless Steel
Flag #5 - Copper

As they start to heat the metal, heat is conducted along each rods which will melt the wax when the heat reaches the end of the rod, which will cause the flag to drop off. As the rate of thermal conductivity of each metal is different, the time taken for each flag is different as well.

From Fastest to Slowest
#3 -> #5 -> #2 -> #1 -> #4

So, from the experiment, we can see that aluminum is the best conductor of heat out of the 5 metals but stainless steel is not as good as the others.

Why does different metals have different rate of thermal conductivity?
The rate of thermal conductivity is depends on many factors such as the amount of free electrons there is, how fast the free electrons move and how far they have to move before colliding into something else and change direction(e.g. electron)

How fast a metal conducts heat is based on the molecules the metal is made up of. Good conductor of heat have atoms that allows heat to flow right through without having to collide or bump into anything. Some metals do not conduct heat that quickly is because they can't really let the heat to flow right through, making the heat bounce around, thus it takes a longer time to heat up.

Conduction

Conduction is the main mode of heat transfer in solids.
It is the process by which heat is transmitted through a medium from one particle to another.

In conduction, heat is transferred from one atom to another by the vibration of atoms. Heat is also transferred by the movement of free electrons from the hot end to the cool end (which is why metals are good conductors of heat.) Poor conductors of heat are liquids and gases.

Conduction occurs in direct contact
e.g. solid to solid (shaking of hands), solid to liquid (diving into the water)

How Conduction Works
When one end of a rod is heated, the particles at this end of the rod gain energy and start vibrating faster, which will then cause the particles to collide with the other particles. Some of their energy is transferred to the other particles which will let the other particles gain kinetic energy. In this way, heat is passed along by the vibrating particles.