Why is the coefficient of friction for a concrete surface greater than the coefficient of friction for an icy surface?

My physics lab instructs me to estimate the coefficient of friction sliding a block of wood on a table with a wooden surface and sliding it on a plastic lid, which of the two coefficient of friction will be greater.

 Review. A light spring of force constant 3.85N/m is compressed by 8.00 cm and held between a 0.250 kg block on the left and a 0.500-kg block on the right. Both blocks are at rest on a hrizontal surface. The blocks are released simultaneously so that the spring tends to push them apart. Find the maximum velocity each block attains if the coefficient of kinetic friction between each block and the surface is

(a) 0, (b) 0.110, and (c) 0.462. 

Assume the coefficient of static friction is greater than the coefficient friction in every case.