Different materials conduct heat in different ways. This ability to conduct heat is called thermal conductivity.

Thermal conductivity is shown by the letter $k$. It tells us how good a material is at conducting heat. We measure it in units called watts per meter-kelvin (W/(m·K)).

Here are some key points to know:

1. Conductive Materials:

   • Metals like copper and aluminum are really good at conducting heat.
     • For copper, $k = 385$ W/(m·K).
     • For aluminum, $k = 237$ W/(m·K).
   • We often use these metals in things that need to transfer heat well, like cooking tools and heat exchangers.

2. Insulating Materials:

   • Non-metal materials like wood and rubber do not conduct heat well. They are used as insulators.
     • For wood, $k = 0.1 - 0.2$ W/(m·K).
     • For rubber, $k = 0.13$ W/(m·K).
   • Insulators help keep heat from escaping. This makes them very useful in buildings to keep things warm or cool inside.

3. Comparison of Conductivities:

   • The difference in thermal conductivity shows that some materials conduct heat much better than others.
   • For example, ice has a thermal conductivity of $k = 2.2$ W/(m·K), which is about 10-20 times lower than metals.

4. Factors Influencing Conductivity:

   • Several things can affect how well a material conducts heat. These include the material's structure, how dense it is, its temperature, and whether it is solid, liquid, or gas.
   • Generally, gases are not very good at conducting heat compared to solids and liquids. For instance, air has a thermal conductivity of about $k \approx 0.025$ W/(m·K).

Knowing these differences can help us choose the right materials for managing heat in different situations.