As the bright sun shines upon the water the water slowly disappears the same sunlight gives energy to the surrounding plants to convert water and carbon dioxide into sugar and only oxygen gas which change is a physical and which is chemical

Well when the sun makes water dissaper thats usually evaporation.

The chemical changes is when the plants absorb the energy from the sunlight and convert water and carbon dioxide into sugar and oxygen gas. Physically nothing has changed. The plant still looks the sam changes occur internally these internal changes are chemical in nature. 

Dsolubility let me know if you have any other questions for chemistry