When sodium metal is added to water, an orange flame is observed on the metal surface. based on this observation, what can best be concluded?

a physical change occurs because the metal gets smaller.
a chemical reaction occurs because the liquid becomes cloudy.
a chemical reaction occurs because heat and light are given off.
a physical change occurs because vapor is released into the air.

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.