Ozone Basics
What layer of the atmosphere contains most of the Earth’s ozone?
Stratosphere
What is the term used for the seasonal thinning of ozone over Antarctica?
Ozone hole
What does CFC stand for?
Chlorofluorocarbon
Which type of UV radiation is most dangerous but blocked by ozone?
UV-C
What international agreement was signed to phase out ozone-depleting substances?
Montreal Protocol (1987)
What is the chemical formula for ozone?
O3
What group of human-made chemicals caused major ozone depletion?
CFCs (chlorofluorocarbons)
What releases chlorine atoms that destroy ozone molecules?
UV rays breaking down CFCs
What are two human health impacts of increased UV exposure?
Skin cancer and cataracts
Name one replacement chemical for CFCs.
HCFCs or HFCs
What type of radiation does ozone absorb?
UV (ultraviolet) radiation
Which natural event can worsen ozone depletion by releasing chlorine into the stratosphere?
Volcanic eruptions
Write the basic chemical reaction that destroys ozone (simplified).
Cl + O₃ → ClO + O₂
How does increased UV affect primary producers in oceans?
It reduces phytoplankton productivity, disrupting food chains.
Why was the Montreal Protocol successful?
It had global cooperation, clear targets, and financial support for developing nations.
What is the approximate altitude range of the ozone layer?
About 10–50 km above the Earth’s surface
In what decade was the ozone hole first discovered?
1980s
Besides CFCs, name another ozone-depleting substance.
Halons, methyl bromide, or HCFCs
What effect does increased UV have on crops?
It can damage plant tissues and reduce yields.
What organization monitors the state of the ozone layer?
World Meteorological Organization (WMO) or UNEP
Why is ozone considered both “good” and “bad”?
Because stratospheric ozone protects life from UV radiation, while tropospheric ozone is a pollutant harmful to health and vegetation.
What happens to ozone molecules when exposed to chlorine radicals from CFCs?
They are broken apart, reducing ozone concentration through catalytic reactions.
Why is ozone depletion more severe in polar regions?
Because polar stratospheric clouds (PSCs) form in cold conditions, releasing active chlorine during spring.
What role does UV radiation play in smog formation?
It drives photochemical reactions that form ground-level ozone and smog.
Describe one positive feedback loop that could delay ozone recovery.
Warming stratosphere → slower ozone formation OR climate change altering circulation → affecting ozone distribution.