What becomes of the dew that collects on plants and other objects at night?
It is evaporated.
How does the sun hasten the evaporation of the dew?
By supplying the heat needed to change the dew into a vapor, the sun hastens its evaporation.
Why do bread and biscuit become hard when kept a few days?
Because the moisture in them passes off into the air, and thus they become dry and hard.
How can they be kept moist and soft for a longer time?
By keeping them in a covered vessel, so that evaporation will take place more slowly, they may be kept moist for a longer time.
Radiation.
When we stand near the fire, why do we feel warm?