CBSE Class 10 Science 2022 · Paper 31/4/3 · Question 11

The chemical is chlorofluorocarbons (CFCs). They were used mostly by the companies manufacturing refrigerators (and air-conditioners), where CFCs served as the refrigerant, and fire extinguishers, the two uses NCERT names; CFCs were also used as propellants in aerosol sprays. (i) Upper layers of the atmosphere: CFCs drift up to the upper atmosphere, where ultraviolet radiation breaks them and sets chlorine atoms free. These break ozone (${\text{O}}_3$) down to oxygen (${\text{O}}_2$), so the ozone layer becomes thinner (ozone depletion). (ii) Organisms on the earth: the thinner ozone layer lets more of the Sun's ultraviolet radiation reach the earth. This radiation is highly damaging to organisms: it can cause skin cancer in human beings, damage the eyes and weaken immunity, and it harms plants and other organisms.