Final answer:
The metal of a bike feels colder than the wood of a porch on a cold winter morning due to the difference in thermal conductivity between the two materials.
Step-by-step explanation:
On a cold winter morning, the metal of a bike feels colder than the wood of a porch because of the difference in thermal conductivity between the two materials. The metal has a higher thermal conductivity, which means it conducts heat away from your body faster than the wood does. This results in the metal feeling colder to the touch compared to the wood.