Boiling point how many degrees

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AddThis use cookies for handling links to social media. What about some hydrogen and some oxygen? The bubbles are water vapor—they are small pockets of water in the gas phase. I mean, they couldn't be air. Where would this air come from? The only option is that the bubbles are made of water vapor. So, what is happening to make these boiling bubbles of water vapor? It's all about temperature and vapor pressure. As the temperature of the water increases, the average speed of the water particles also increases.

At some point, water molecules have enough energy to push back other water molecules in the liquid phase to form a bubble. But you have to have the water hot enough so that the particles are moving fast enough.

It's also about the vapor pressure. In order to keep the bubble from collapsing, the pressure inside the bubble must be equal to the pressure outside the bubble. Inside the bubble is the vapor pressure and outside is the water pressure. This means that for water to boil, the temperature must increase until the vapor pressure is equal to the outside pressure and a bubble can form. What about that external pressure? That depends on two things. First, the water itself. In order for the water to not collapse, the deeper water must have a higher pressure.

So, the water pressure depends on the depth, the density of water and the gravitational field since it's due to the weight of the water.

For a typical glass of water, the pressure at 2 centimeters below the surface is only a 0. And that is the second thing that contributes to the total pressure—the atmosphere.

The atmosphere also pushes down on the surface of the liquid to increase the pressure in the liquid. Now for the fun part. What if I decreased the atmospheric pressure pushing on some liquid water? This would reduce the pressure in the liquid also. If I reduce this pressure enough, I can bring it down to the same level as the vapor pressure. Now the water particles have enough energy to form their tiny little boiling bubbles—without the need to increase the temperature.

I can even get water to boil at room temperature. Yes, you need a vacuum pump and a strong container to get this to work—but you can do it. Notice that I hold onto the boiling water flask just to prove that it's not hot. Trust me. The reason for this variation comes down to the differences in atmospheric pressure at different elevations. Even at the same level, there are natural fluctuations in air pressure; regions of high and low pressure are commonly shown as parts of weather forecast, but these variances are slight compared to the changes as we go higher up into the atmosphere.

This can be thought of as the tendency of molecules in a liquid to escape into the gas phase above the liquid. Vapour pressure increases with increasing temperature, as molecules move faster, and more of them have the energy to escape the liquid. When the vapour pressure reaches an equivalent value to the surrounding air pressure, the liquid will boil.

As we move higher into the atmosphere and the atmospheric pressure drops, so too does the amount of vapour pressure required for a liquid to boil. Due to this, the temperature required to reach the necessary vapour becomes lower and lower as we get higher above sea level, and the liquid will therefore boil at a lower temperature. In fact, adding any solute to water will increase the boiling temperature, as it reduces the vapour pressure, meaning a slightly higher temperature is required in order for the vapour pressure to become equal to atmospheric pressure and boil the water.