CBSE Class 10 Science 2018 · Paper 31/1/C · Question 18(b)

(a) The process is photosynthesis. Green plants show autotrophic nutrition: they make their own food (carbohydrates such as glucose) from simple inorganic substances, carbon dioxide and water, using the energy of sunlight absorbed by chlorophyll; the food not used at once is stored as starch. Raw materials: carbon dioxide (from the air, through the stomata) and water (from the soil, through the roots); sunlight and chlorophyll are also needed. Equation: $6{\text{CO}}_2+12{\text{H}}_2\text{O}\underset{\text{Chlorophyll}}{\overset{\text{Sunlight}}{\to }}{\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2+6{\text{H}}_2\text{O}$ (b) (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.