Ozone Depletion

Question 1

What does the ozone absorb?

Answer 1

Harmful UV radiation
All of UVC
Most of UVB
Some of UVA

Question 2

Which layer of the atmosphere is the ozone?

Answer 2

The stratosphere

Question 3

In which layer of the atmosphere is the ozone not supposed to be (harmful)?

Answer 3

The troposphere

Question 4

How is the ozone layer formed from the release of CFCs into the atmosphere?

Answer 4

1. CFCs released into environment by industry, rises up to stratosphere
2. Sunlight breaks CFCs up, releasing Chlorine
3. Chlorine reacts with ozone (O3) and destroys Ozone
4. More reactions course more depletion

Question 5

UVC is mostly absorbed by Diatomic oxygen molecules and splits into monatomic oxygen:

Answer 5

O2 + UV —> O + O

Question 6

UVB is absorbed by ozone and splits this molecule into diatomic oxygen and monatomic oxygen:

Answer 6

O3 + UV —> O2 + O

Question 7

Monatomic oxygen is very reactive and combines with diatomic oxygen molecule to form ozone, heat is released:

Answer 7

O + O2 —> O3

Question 8

What is a combination of active processes that cancel out each other’s effects so that there is no overall change?

Answer 8

Dynamic Equilibrium

Question 9

What are some effects of UVB on living organisms?

Answer 9

Skin cancer
Cataracts
Sunburn
Cuticle damage on plants

Question 10

What is an example of a halogen that causes ozone depletion in the stratosphere?

Answer 10

Chlorine

Question 11

What is the history and the properties of CFCs?

Answer 11

CFCs are not natural - artificial and manufactured by humans

Non-flammable, non-toxic, tasteless, odourless and chemically stable

Used in the manufacturing of aerosol sprays, blowing agents for foams, packaging materials, as solvents and as refrigerants

First synthesised in 1928 by Thomas Midgley Jr. of General Motors

Doesn’t dissolve in water

Dissolve oil and greases without damaging electrical parts

Question 12

Sources of CFCs:

Answer 12

Fridges
Aerosol sprays
Blowing agents for foams
Packing materials
Solvent

Question 13

What is the Rowland-Molina principle?

Answer 13

Proposed by scientists Mario J. Molina and F. Sherwood Rowland in 1974, suggests that chlorofluorocarbons (CFCs)—commonly used in refrigeration and aerosol products—are the main agents behind ozone layer degradation.

Extra:

CFCs are stable and persistent in the atmosphere

Travel/move to the stratosphere

High energy UV break bonds

Single monoatomic Cl is very reactive

Reaction with O stops the natural formation of O3

Question 14

Chemistry of the Ozone Layer

Answer 14

Question 15

Chlorofluorocarbons (CFCs)

Answer 15

Question 16

Why is ozone depletion greatest at Polar Regions?

Answer 16

Polar vortex winds and polar stratospheric cloud creates very cold conditions.

Cold, dark conditions means Cl is released from ice crystals, destroying the ozone layer (Cl free radicals destroy ozone layer).

Question 17

What other gases cause ozone depletion?

Answer 17

(Chlorine)
Halogens - e.g Bromine

Question 18

What is ozone measured in?

Answer 18

Dobson Units

Normal level of ozone is 300 DU

Anything less than 300 DU is considered part of a hole

Question 19

What are the methods of measuring ozone in the stratosphere?

Answer 19

Satellites measure UV reflection from Earth’s surface - more UV reflection means more UV got through to surface, therefore the worse the conditions of the ozone layer.

Helium balloons / high flying aircraft in stratosphere collecting air samples.

UV detectors at ground level

Question 20

What are the disadvantages of the methods used to measure ozone in the stratosphere?

Answer 20

Satellites are expensive

UV detectors can only detect UV six months of the year

Balloons are scientific to measure in the stratosphere

Question 21

What is the Montreal Protocol 1987?

Answer 21

The Montreal Protocol, finalized in 1987, is a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS).

Almost every country in the world, agreed and signed.

Question 22

What did the Montreal Protocol agree to specifically?

Answer 22

Agreed to phase out and ban the use of CFCs

Alternative propellant HCFCs to be banned by 2030

Propellants used today HFCs, propane and butane

Alternatives to aerosols sprays - pump action, trigger spray, roll on/stick deodorant

Safe and regulated disposal of fridges

Question 23

What has the Montreal protocol achieved?

Answer 23

The Montreal Protocol has been successful in slowing and reversing the increase of ozone-depleting gases (halogen source gases) in the atmosphere.