You are heating water in a pot on the stove. Shortly before the water boils properly, bubbles of steam begin rising from the bottom of the pot but vanish before they reach the water's surface. What happens to those bubbles?

When you heat water, it undergoes a phase change from liquid to gas. This occurs when the water reaches its boiling point of 100°C (212°F) at standard atmospheric pressure. During this phase change, the water molecules gain enough energy to break free from the liquid phase and enter the gas phase, forming steam. This process involves the absorption of energy, also known as the latent heat of vaporization.
To visualize, picture water molecules moving faster and faster as they get hotter. Once they reach a high enough speed, they escape the liquid state and become steam, a gas. Understanding phase changes is crucial because they explain how substances transition between solid, liquid, and gas states.

Steam bubbles are formed when water at the bottom of the pot heats up to its boiling point. These bubbles are essentially pockets of water vapor (steam) trapped within the liquid water. As you continue to heat the pot, more steam bubbles form, giving you that characteristic boiling look.
However, if the water above the bottom layer is not yet at boiling temperature, these steam bubbles may collapse before reaching the surface. This happens because the surrounding cooler water absorbs the heat from the steam bubbles, cooling the vapor inside back into liquid water. So, the bubbles disappear as they condense back into the liquid before reaching the surface.

This process can be summarized as follows:
• Water at the bottom reaches boiling point and forms steam bubbles.
• Bubbles rise towards the surface.
• Cooler water layers absorb heat from the bubbles.
• Bubbles condense back into water before reaching the surface.

Condensation is the process where gas molecules lose energy and transition back to a liquid state. In the context of boiling, condensation happens when the steam bubbles rise through cooler layers of water and lose their heat. As they lose this thermal energy, they revert from vapor to liquid.
This process is essentially the reverse of boiling. When the heat from the steam bubbles is transferred to the surrounding cooler water, the bubbles no longer have enough energy to remain in the vapor phase and collapse back into liquid form. Condensation is a fundamental concept that explains various everyday phenomena, such as the formation of dew on grass in the morning or the droplets that form on the outside of a cold glass.
Remember, for condensation to occur, the gas must come in contact with a surface or medium that is cooler than its temperature, facilitating the loss of energy and the phase change back to liquid.