Answer: Evaporation and heat loss to the surrounding.
Step-by-step explanation:
The process is known as evaporation.
Evaporation takes place at any temperature but increases with increase in temperature. The molecules of water evaporate, that is, escape into the atmosphere thereby causing the volume of water to reduce.
The temperature decreases due to heat loss from the water into the surrounding. This will cause the temperature of the water to drop.