Heat that flows by conduction is the transfer of thermal energy between substances in contact. for this to happen, what must occur?
a. the two systems must be the same temperature.
b. the two systems must not be touching each another.
c. one system must have higher kinetic energy than the other system.
d. the thermal energy of one system must be the same as the thermal energy of the other system.

The small bags of silica gel you often see in a new shoe box are placed there to control humidity. despite its name, silica gel is a solid. it is a chemically inert, highly porous, amorphous form of sio2. because water vapor readily adsorbs onto the surface of silica gel, it acts as a desiccant. despite not knowing mechanistic details of the adsorption of water onto silica gel, from the information provided you should be able to make an educated guess about the thermodynamic characteristics of the process. predict the signs for δg, δh, and δs for the adsorption of water.