Final answer:
The stability of liquid methane before 2007 was due to the strong intermolecular forces that prevented it from changing phase. Changes in both pressure and temperature make it difficult to predict such phase changes. Additionally, methane is flared instead of released to reduce its greenhouse gas impact.
Step-by-step explanation:
The question about liquid methane not changing phase before 2007 can be answered by considering the concepts of intermolecular forces and the energy of particles. A substance exists as a solid, liquid, or gas depending on the balance between these two factors. For methane, the intermolecular forces must have been strong enough to keep it as a liquid despite the changes that occurred. Moreover, the prediction of phase changes can be difficult when multiple properties of a gas are changing, including pressure and temperature.
Additionally, methane is a gas that does not remain in the atmosphere as long as carbon dioxide (CO₂); therefore, it is often flared at drill sites. The reason for this practice is to prevent methane from escaping into the atmosphere, as methane is a potent greenhouse gas. This is relevant when considering the environmental impact of methane as a substance.
The behavior of gases is also closely linked to temperature, as demonstrated by the historical understanding of gas laws and its role in the development of chemistry. For instance, when a gas expands, such as methane when it is vented or flared, it cools down, akin to the cooling effect when gas is sprayed from an aerosol can.