Why does dew form on grass in the morning?

Answer: Air cools and moisture condenses

Air cools and moisture condenses ✓ — Correct! At night, grass and ground cool by radiating heat to space. Air touching these cool surfaces drops below its dew point - the temperature where water vapor condenses. Moisture in the air then condenses into droplets on the cool grass. Clear, calm nights create the most dew because heat radiates away efficiently without clouds or wind!

Morning fog settles on grass — Wrong. Dew isn't fog settling - it's water vapor condensing directly onto cool surfaces. Fog is suspended droplets in air; dew forms on surfaces when they cool below the air's dew point.

Underground water rises up — Wrong. Dew doesn't come from underground - it forms from water vapor in the air. When surfaces cool overnight, air moisture condenses on them as tiny droplets.