CBSE Class 10 Science 2019 · Paper 31/2/1 · Question 15

Function: at the higher levels of the atmosphere, ozone (${\text{O}}_3$) shields the surface of the Earth from the harmful ultraviolet (UV) radiation of the Sun, which damages organisms and can cause skin cancer in human beings. Production: high-energy UV radiation splits some oxygen molecules into free oxygen atoms, and these atoms combine with oxygen molecules to form ozone: ${\text{O}}_2\stackrel{\text{UV}}{\to }\text{O}+\text{O}$, then $\text{O}+{\text{O}}_2\to {\text{O}}_3$. Chemicals responsible: chlorofluorocarbons (CFCs), used as refrigerants and in fire extinguishers. Reducing their use: minimise the leakage of CFCs from refrigerators and air conditioners, and replace CFCs with ozone-friendly substitute chemicals (CFC-free refrigerators, air conditioners and fire extinguishers).