Understanding the Sequence of Ozone Depletion and Skin Cancer

The question asks us to arrange a series of events in the correct chronological sequence, starting from bringing a fridge into a house and ending with ultra violet (UV) radiation causing skin cancer. This chain of events involves the use of certain chemicals, their impact on the atmosphere, and the subsequent health effects.

Let's analyze each event provided:

• (A) Ultra violet radiation causes skin cancer: This is the final health effect.
• (B) High levels of chlorine and bromine compounds in the stratosphere: These compounds are responsible for ozone depletion.
• (C) Fridge brought to the house: This is often the starting point in consumer use of products containing ozone-depleting substances.
• (D) Chlorofluorocarbon used as cooling agent: Chlorofluorocarbons (CFCs) were commonly used as refrigerants in older fridges.
• (E) Depletion of ozone layer: This occurs due to the action of chlorine and bromine compounds in the stratosphere.

Establishing the Chronological Order of Events

Let's piece together the events logically to determine the correct sequence:

1. The process begins with the use of products containing ozone-depleting substances. Bringing a fridge into the house (C) that uses such substances is a starting point from a consumer perspective.
2. The specific substance mentioned is Chlorofluorocarbon (CFC) used as a cooling agent (D) in the fridge.
3. Over time, CFCs escape into the atmosphere and rise to the stratosphere. In the stratosphere, these CFCs break down, leading to High levels of chlorine and bromine compounds (B).
4. These high levels of chlorine and bromine compounds act as catalysts, causing the Depletion of the ozone layer (E).
5. A depleted ozone layer allows more Ultra violet (UV) radiation to reach the Earth's surface, which can cause skin cancer (A).

Therefore, the logical sequence of events is: Fridge brought to the house → Chlorofluorocarbon used as cooling agent → High levels of chlorine and bromine compounds in the stratosphere → Depletion of ozone layer → Ultra violet radiation causes skin cancer.

Mapping this to the given letters, the sequence is (C), (D), (B), (E), (A).

Summary of the Sequence

The sequence (C), (D), (B), (E), (A) correctly describes the environmental and health impacts linked to the use of CFCs and ozone depletion.

Revision Table: Key Concepts

Additional Information: Ozone Depletion Process

The process of ozone depletion involves several steps once ozone-depleting substances like CFCs reach the stratosphere:

• UV radiation in the stratosphere breaks down CFC molecules, releasing chlorine atoms (<code>\[\text{Cl}]</code>).
• A single chlorine atom can react with an ozone molecule (<code>\[\text{O}_3}]</code>), breaking it apart and forming chlorine monoxide (<code>\[\text{ClO}]</code>) and oxygen gas (<code>\[\text{O}_2}]</code>). The reaction is <code>\[\text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2]</code>.
• The chlorine monoxide molecule can then react with a free oxygen atom (<code>\[\text{O}]</code>), releasing the chlorine atom and forming oxygen gas. The reaction is <code>\[\text{ClO} + \text{O} \rightarrow \text{Cl} + \text{O}_2]</code>.
• The released chlorine atom is then free to destroy another ozone molecule. This catalytic cycle means one chlorine atom can destroy thousands of ozone molecules before it is removed from the stratosphere.
• Bromine atoms (<code>\[\text{Br}]</code>) from substances like halons also deplete ozone through similar catalytic cycles, and are even more efficient at destroying ozone than chlorine atoms.
• The presence of high levels of these reactive chlorine and bromine compounds leads to significant depletion of the protective ozone layer.
• The thinning ozone layer results in more harmful UV-B radiation reaching the Earth's surface, increasing the risk of skin cancer, eye damage (like cataracts), and harm to ecosystems.

International agreements like the Montreal Protocol have been successful in phasing out the production and consumption of many ozone-depleting substances, leading to a slow recovery of the ozone layer.