Question

Dry ice is effective in seeding clouds because (1) \(\mathrm{CO}_{2}\) and \(\mathrm{II}_{2} \mathrm{O}\) have similar crystal structure (2) it increases water content of the cloud (3) \(\mathrm{CO}_{2}\) molecules offer nucleus for condensation (4) upon sublimation, it lowcrs the temperature of water

Short answer

Option (3) is correct: \(\text{CO}_2\) molecules offer a nucleus for condensation.

Step-by-step solution

Analyze the Question

The question asks why dry ice (solid \(\text{CO}_2\)) is effective in seeding clouds. There are four provided options.

- Check the Crystal Structure

Option (1) states \(\text{CO}_2\) and \(\text{H}_2\text{O}\) have similar crystal structures. \(\text{CO}_2\) is a simple linear triatomic molecule, whereas \(\text{H}_2\text{O}\) forms a bent molecular structure. This means their crystal structures are not similar.

- Consider Water Content Increase

Option (2) suggests dry ice increases the water content of the cloud. Dry ice directly sublimates into carbon dioxide gas, not water, so it does not increase the water content.

- Evaluate Nucleus for Condensation

Option (3) states that \(\text{CO}_2\) molecules offer a nucleus for condensation. During cloud seeding, a substance is needed to allow water vapor to condense, so this might be a valid reason.

- Review Temperature Effect

Option (4) claims that upon sublimation, dry ice lowers the temperature of water. While this is true, it is not the main reason why dry ice is used in cloud seeding.

Conclusion

The most accurate reason why dry ice is effective for seeding clouds is that \(\text{CO}_2\) molecules offer a nucleus for condensation, as stated in Option (3).

Key concepts

headline of the respective core concept

Condensation nuclei are tiny particles in the air that water vapor needs to condense onto. This is essential for cloud formation. Without these particles, water vapor cannot easily transition into liquid droplets. Common condensation nuclei include dust, soot, and salt particles.
When we talk about cloud seeding using dry ice, the dry ice provides these necessary nuclei. In the atmosphere, dry ice (solid carbon dioxide) undergoes a process called sublimation.
This is crucial as it forms condensation nuclei, aiding the condensation process and promoting cloud formation.

headline of the respective core concept

Sublimation of dry ice is the process where dry ice changes directly from a solid to a gas without going through a liquid phase. This occurs at a temperature of -78.5°C.
When dry ice is used in cloud seeding, it sublimates into carbon dioxide gas upon exposure to the atmosphere.
This sublimation cools the surrounding air, facilitating the condensation of water vapor. Cooling the air is crucial because it allows water vapor to condense around the newly formed nuclei, eventually forming cloud droplets.

headline of the respective core concept

The cloud seeding process involves dispersing substances like dry ice or silver iodide into the atmosphere to stimulate cloud formation and precipitation. Here's how it works:
1. **Introduction of Seeding Agents**: Dry ice is dispersed into clouds via aircraft.
2. **Sublimation**: The dry ice sublimates, releasing carbon dioxide gas which cools the air.
3. **Formation of Condensation Nuclei**: The cooling effect and presence of carbon dioxide provide nuclei around which water vapor can condense.
4. **Cloud Formation**: As water vapor condenses on these nuclei, cloud droplets form, increasing the likelihood of precipitation.

headline of the respective core concept

Crystal structures refer to the arrangement of atoms or molecules in a solid. For water (H₂O), the crystal structure forms a hexagonal lattice in ice.
Carbon dioxide (CO₂) in its solid state (dry ice) forms a different structure, although it also has a crystalline form.
However, their crystal structures are not similar. The effectiveness of dry ice in cloud seeding isn't due to any similarity in their crystal structures, but rather due to the cold temperatures and nuclei provided by the sublimation process.
Thus, Option (1) in the exercise is not a valid reason for the effectiveness of dry ice in cloud seeding.