Explain what happens when a liquid boils.

When we think about how a substance changes from one state of matter to another, we're discussing phase transitions. Boiling is a type of phase transition where a liquid turns into a gas. It's an intriguing phenomenon where the substance fundamentally alters its arrangement. In this case, the individual particles of a liquid, which are relatively close together, acquire enough energy to break free from their liquid bonds and become a gas, where the particles are much further apart.

Picture this scenario: When you heat water in a kettle, the water doesn't immediately turn into steam. First, it undergoes a phase transition. As the water temperature increases, the molecules move faster, colliding more and pushing against each other until they have enough energy to create steam, which consists of dispersed water molecules in the air. This phase transition is not just unique to boiling water but occurs in many other substances when they reach specific temperatures and pressures.

The term latent heat of vaporization sounds complex, but it represents the amount of energy that is required to turn a liquid into a gas without changing its temperature. Think about it as the 'hidden energy' that's necessary to free the liquid molecules from their buddies and allow them to float away as a gas. To better understand, let's use the example of boiling water again.

When you continue to heat the water after it starts boiling, you won't see the temperature go up, but you will notice more steam. The heat energy you're adding doesn't increase temperature; instead, it's absorbed and used to transform the water from liquid to gas, and this heat is what we call the latent heat of vaporization. It's important because it helps us understand why boiling liquid doesn't instantly evaporate and why certain processes, like cooking or industrial cooling, take the time they do - they're dependent on the amount of this latent heat that the substance can absorb.

The term vapor pressure might evoke the image of pressure in vapors similar to air in a tire, but it's a bit different when we're talking about liquids and gases. In simple terms, vapor pressure is the pressure created by the vapor released by a liquid. Every liquid has a point at which its vapor pressure is equal to the surrounding atmospheric pressure. When the liquid reaches this point, it begins to boil.

Let’s picture this: If you left a glass of water out, water would slowly evaporate. The water molecules escape into the air until there’s as much tendency for them to return to the liquid as there is for them to fly off - that's the vapor pressure in action. At sea level, atmospheric pressure is 'normal', so water boils at 100°C. However, high up on a mountain, the atmospheric pressure is lower, so water boils at a lower temperature because it reaches the needed vapor pressure to boil at a lower temperature too. Understanding vapor pressure helps us figure out how and why different liquids boil at different temperatures, which can be important for a massive range of things, from cooking to science experiments.