Why Does Water Boil Faster at Higher Altitude?

Are you familiar with the art of cooking? No, pouring cereal in a bowl does not count! We are referring to the skill of combining different ingredients and cooking them to create a tasty meal.

As human beings, we understand that eating is necessary for survival. With the convenience of restaurants and pre-packaged foods available at grocery stores, cooking is not a skill that we necessarily need in order to feed ourselves.

In fact, many individuals may not learn how to cook until they leave home for college or a career. If you find yourself in your twenties and your cooking abilities are limited to microwaving a frozen meal, your friends may jokingly say that you don’t even know how to boil water.

Of course, this is quite absurd, isn’t it? Boiling water is one of the most basic skills that anyone can quickly master. All you need to do is fill a pot with water and place it on a heat source until it reaches a boiling temperature of 212°F. What could be easier?

However, if you decide to test your water-boiling skills in Denver, Colorado, or at a high altitude, you may discover that it is not as simple as it seems. This is because water only boils at 212º F at sea level. At higher altitudes, the boiling point of water decreases, resulting in longer cooking times.

The boiling point of water is one of the scientific “facts” that we learn early in school. Everyone knows that the boiling point of water is 212º Fahrenheit or 100º Celsius. However, this fact is true at sea level and can vary under different conditions.

One such condition is a change in altitude. At higher altitudes, the air pressure is lower. As we ascend into the atmosphere, there is less air pushing down on us. So why does this affect the boiling point of water?

To boil water, heat energy needs to be applied. As the water molecules absorb energy, the bonds holding them together begin to break. The water will boil or turn into vapor when its internal vapor pressure equals the pressure exerted on it by the atmosphere. When this happens, bubbles start to form and the water boils.

When the atmospheric pressure is lower, such as at higher altitudes, it requires less energy to bring water to its boiling point. Less energy means less heat, resulting in water boiling at a lower temperature at higher altitudes.

Some people believe that a lower boiling point means that food will cook faster at higher altitudes. However, the opposite is true. If you want to boil an egg, it will take slightly longer at a higher altitude.

This is because cooking involves heating food to a specific temperature for a certain duration. If the temperature is lowered due to altitude (as in the case of boiling water), the cooking time needs to be extended to ensure that the food is fully cooked!

Give It a Try

Are you ready to elevate your knowledge? Get a friend or family member and explore the following activities:

  • Are you interested in participating in a global science experiment with other children? Visit the website to explore “Under Pressure: Boiling Water.” You will need assistance from an adult friend or family member. The objective is to determine the boiling point of water in your location. You will require a few basic materials to begin. Once you have completed the experiment, you can enter your findings online and compare them with results from around the world!
  • Are you curious whether it makes a difference if you start with hot or cold water when boiling it? Find out by conducting your own experiment. Follow the instructions for the “Hot vs. Cold Water: Boiling Experiment” online. What is your hypothesis? Write it down, then proceed with the experiment. What did you discover? Was your initial hypothesis correct?
  • If you frequently cook, you may have come across instructions that advise adding salt to boiling water. Have you ever wondered what effect salt has on the boiling point of water? Explore this by conducting a simple experiment. Read “The Effect of Salt on the Boiling Temperature of Water” to learn more. Remember to seek assistance from an adult friend or family member before conducting the experiment. Share your findings with them!

Sources of Wonder

  • http://www.chemistry.co.nz/cooking_altitudes.htm
  • http://www.pewresearch.org/fact-tank/2015/09/14/does-waters-boiling-point-change-with-altitude-americans-arent-sure/

FAQ

1. Why does water boil faster at higher altitude?

Water boils when its vapor pressure equals the atmospheric pressure. At higher altitudes, the atmospheric pressure is lower compared to sea level. Therefore, water requires less energy to reach its boiling point because the vapor pressure can be achieved at a lower temperature. This is why water boils faster at higher altitudes.

2. How does altitude affect the boiling point of water?

As altitude increases, the atmospheric pressure decreases. Since the boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure, the lower atmospheric pressure at higher altitudes results in a lower boiling point for water. This means that water will boil faster at higher altitudes compared to sea level.

3. What happens to water molecules at higher altitudes that make them boil faster?

At higher altitudes, the lower atmospheric pressure reduces the pressure exerted on the water molecules. This causes the water molecules to move more freely and escape from the liquid phase into the gas phase at a lower temperature. Therefore, water molecules at higher altitudes have a higher chance of gaining enough energy to overcome the intermolecular forces and transition to the gas phase, resulting in faster boiling.

4. Does water reach a higher temperature at higher altitudes?

No, water does not reach a higher temperature at higher altitudes. The boiling point of water decreases with increasing altitude due to the decrease in atmospheric pressure. While water may boil faster at higher altitudes, it does not mean that it reaches a higher temperature. The temperature at which water boils remains the same, but it requires less energy to reach that temperature due to the lower atmospheric pressure.

5. Can we cook food faster at higher altitudes?

Yes, cooking food can be faster at higher altitudes due to the lower boiling point of water. Since water boils at a lower temperature, it can transfer heat more efficiently to the food, resulting in faster cooking. However, it is important to adjust cooking times and temperatures accordingly, as the decrease in atmospheric pressure can also affect other cooking processes such as baking and simmering. It is recommended to follow altitude-specific cooking instructions or make appropriate adjustments to cooking times and temperatures when cooking at higher altitudes.

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