CO2 is indeed heavier than air, but its behavior in the atmosphere is influenced by various factors such as temperature, pressure, and molecular motion. The concept of gases rising or sinking is determined by their density relative to the surrounding air.
When we say that CO2 is "heavier" than air, we mean that it has a higher molar mass than the predominant components of air, which are nitrogen (N2) and oxygen (O2). However, the density of a gas depends not only on its molar mass but also on its temperature and pressure.
In the Earth's atmosphere, the distribution of gases is not solely determined by their molar masses. Instead, it is primarily influenced by convection currents and the process of diffusion. When CO2 is released into the atmosphere, it initially disperses and mixes with the surrounding air due to molecular motion and diffusion.
Convection currents play a significant role in gas movements in the atmosphere. These currents are generated by temperature differences in different regions. Warmer air tends to rise because it becomes less dense than the surrounding cooler air. Cooler, denser air sinks. This convective motion causes vertical mixing in the atmosphere, allowing gases to be transported and dispersed.
In the case of CO2, although it is heavier than air, it can still be transported upwards due to convection currents. When CO2 is released near the ground, it mixes with the surrounding air and becomes part of the convective motion. The warmer air near the ground, which is less dense, rises carrying the CO2 with it.
It's important to note that the rise of CO2 in the atmosphere is a gradual process influenced by various factors. The dispersal and movement of CO2 depend on the specific conditions, such as wind patterns, temperature gradients, and the concentration of CO2 being released.
In summary, while CO2 is heavier than air, it can still rise in the atmosphere due to convective motions and the mixing of gases facilitated by diffusion. The distribution and movement of gases in the atmosphere are complex and influenced by multiple factors beyond their molar masses.