The Heat Limit: Exploring Water's Extreme Temperature Threshold

How hot can a pot of water get? Well, it depends. At sea level, water boils at 100°C (212°F) and freezes at 0°C (32°F). If you're at a higher altitude, water will boil at a lower temperature. For example, in Bogotá, which is 8,000ft above sea level, water boils at around 14 or 15 degrees cooler than at sea level.

It is possible to heat water above its boiling point without it boiling. This is called superheating and can be achieved by heating water in a smooth container with minimal disturbance. However, superheated water can suddenly and violently boil if disturbed, so it's not something you'd want to try at home!

Boiling point depends on pressure

The boiling point of a substance is the temperature at which the vapour pressure of a liquid equals the pressure surrounding the liquid, and the liquid changes into a vapour. The boiling point of a liquid varies depending on the surrounding environmental pressure. A liquid in a partial vacuum, i.e. under lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure.

The higher the atmospheric pressure, the more energy is required for liquids to boil, and the higher the boiling point. Atmospheric pressure is the pressure exerted by the weight of the air molecules above the liquid. In an open system, this can be visualised as air molecules colliding with the surface of the liquid and creating pressure. This pressure is transmitted throughout the liquid and makes it more difficult for bubbles to form and for boiling to take place.

At sea level, pure water boils at 100°C at standard pressure (1 atm). However, at 1,905m altitude, water boils at 93.4°C. The The boiling point of a substance is the temperature at which the vapour pressure of a liquid equals the pressure surrounding the liquid, and the liquid changes into a vapour. The boiling point of a liquid varies depending on the surrounding environmental pressure. A liquid in a partial vacuum, i.e. under lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure.

At higher altitudes, where the atmospheric pressure is much lower, the boiling point is also lower. For example, at 1,905 metres (6,250 ft) altitude, water boils at 93.4°C (200.1°F). The boiling point increases with increased pressure up to the critical point, where the gas and liquid properties become identical. The boiling point cannot be increased beyond the critical point.

The pressure of gas above a liquid affects the boiling point. The greater the pressure, the more energy required for liquids to boil, and the higher the boiling point. In an open system, this can be visualised as air molecules colliding with the surface of the liquid and creating pressure. This pressure is transmitted throughout the liquid and makes it more difficult for bubbles to form and for boiling to take place. If the pressure is reduced, the liquid requires less energy to change to a gaseous phase, and boiling occurs at a lower temperature.

The boiling point of water at standard pressure (the air pressure that exists at sea level) is 212°F (100°C). However, at higher altitudes, the boiling point of water decreases. For example, in Bogotá, which is 8,000 feet above sea level, water that appears to be around 165°F is, in reality, 14-15 degrees cooler.

The boiling point of a liquid depends on temperature, atmospheric pressure, and the vapour pressure of the liquid. When the atmospheric pressure is equal to the vapour pressure of the liquid, boiling will begin.The boiling point of a substance is the temperature at which the vapour pressure of a liquid equals the pressure surrounding the liquid, and the liquid changes into a vapour. The boiling point of a liquid varies depending on the surrounding environmental pressure. A liquid in a partial vacuum, i.e. under lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure.

At higher altitudes, where the atmospheric pressure is much lower, the boiling point is also lower. For example, at 1,905 metres (6,250 ft) altitude, water boils at 93.4°C (200.1°F). The boiling point increases with increased pressure up to the critical point, where the gas and liquid properties become identical. The boiling point cannot be increased beyond the critical point.

The pressure of gas above a liquid affects the boiling point. The greater the pressure, the more energy required for liquids to boil, and the higher the boiling point. In an open system, this can be visualised as air molecules colliding with the surface of the liquid and creating pressure. This pressure is transmitted throughout the liquid and makes it more difficult for bubbles to form and for boiling to take place. If the pressure is reduced, the liquid requires less energy to change to a gaseous phase, and boiling occurs at a lower temperature.

The boiling point of water at standard pressure (the air pressure that exists at sea level) is 212°F (100°C). However, at higher altitudes, the boiling point of water decreases. For example, in Bogotá, which is 8,000 feet above sea level, water that appears to be around 165°F is, in reality, 14-15 degrees cooler.

The boiling point of a liquid depends on temperature, atmospheric pressure, and the vapour pressure of the liquid. When the atmospheric pressure is equal to the vapour pressure of the liquid, boiling will begin.

Boiling water can be superheated

Superheating can occur when water is heated in a microwave because the water may remain undisturbed during the heating process, so there are no nucleation sites for bubbles to form around. The superheated water may appear cooler than it is because it hasn't visibly boiled. However, if the cup of superheated water is bumped, or another ingredient is added, the water may boil suddenly and violently.

Superheated water is liquid water under pressure at temperatures between the usual boiling point of 100 °C (212 °F) and the critical temperature of 374 °C (705 °F). It is also known as "subcritical water" or "pressurised hot water". Superheated water is stable because of overpressure that raises the boiling point, or by heating it in a sealed vessel with a headspace, where the liquid water is in equilibrium with vapour.

Water's strong hydrogen bonding is responsible for many of its anomalous properties. Over the superheated temperature range, the hydrogen bonds break, changing the properties more than would be expected by increasing temperature alone. Water becomes less polar and behaves more like an organic solvent such as methanol or ethanol. The solubility of organic materials and gases increases, and the water itself can act as a solvent, reagent, and catalyst in industrial and analytical applications, including extraction, chemical reactions and cleaning.

Boiling water can be supercooled

Sudden boiling can be triggered when the superheated water is disturbed, for example, by adding sugar or stirring. This can be dangerous, as the abrupt expansion of steam bubbles can cause hot water to splash and scald.

Supercooling is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. This can occur naturally, for example, in the atmosphere, animals, or plants. Water can be supercooled down to approximately -48.3°C (-54.9°F) without any specialised techniques, although it requires the water to be pure and free of nucleation sites.

Supercooling is of particular interest in the food industry, as it allows for the storage of fruits and vegetables at sub-freezing temperatures without damaging the food cells and changing their colour. It is also necessary for the survival of some creatures and plants in nature.

The Mpemba effect, where initially hot water freezes faster than cold water, is due to the supercooling instability in initially hot water, where nucleation agents are more active.

Boiling water at high altitudes

The boiling point of water is lower at high altitudes due to decreased atmospheric pressure. At sea level, water boils at 100 °C (212 °F). For every 152.4-metre (500 ft) increase in elevation, the boiling point is lowered by approximately 0.5 °C. This means that at 2,438.4 metres (8,000 ft) in elevation, water boils at just 92 °C (198 °F).

The lower boiling point of water at high altitudes has implications for cooking. Food will take longer to cook, and in some cases, it may not be possible to cook certain foods at all, depending on the required temperatures. For example, in Bogotá, which is around 8,000 feet above sea level, it is nearly impossible to poach eggs because the water reaches a full boil before the appropriate poaching temperature is reached.

To compensate for the lower boiling point of water at high altitudes, cooking methods may need to be adjusted. This can involve extending cooking times or using specialised equipment such as a pressure cooker, which can provide higher temperatures by creating a vapour-tight seal and increasing the pressure inside the cooking vessel.

It is worth noting that the impact of high altitude on boiling water is not limited to remote mountain locations. With nearly one-third of U.S. households residing in high-altitude locations, many people may need to consider the effects of altitude on boiling water in their day-to-day cooking.

Boiling water in a pressure cooker

The Instant Pot is a popular pressure cooker that can be used to boil water. It has different functions that allow you to boil water in different ways. One way is to use the pressure setting on the Instant Pot. To do this, add 2-3 cups of water to the pot, close the lid, and set the cooking time to 5 minutes on high pressure. It will take 3-4 minutes for the pot to come up to pressure, and once it does, it will start counting down from 5. After 5 minutes, quickly release the pressure and be careful of any liquid that may come out from the top knob.

Another way to boil water in an Instant Pot is by using the sauté function. This method is perfect if you only need to boil 1-2 cups of water. Pour the desired amount of water into the pot and press the "Sauté Function" button. Set the time for 8 minutes and let the pot do its thing. The water will start to bubble and increase to a full rolling boil. After 8 minutes, you can remove the water or press the "keep warm" function to keep the water hot.

The benefit of using a pressure cooker like the Instant Pot to boil water is that it traps the steam, allowing the water to heat up more quickly. It's also a great option if you don't have an electric kettle or if your stove is too full to fit a large pot of water.

It's important to note that the amount of time it takes for the water to boil will depend on the temperature of the water you start with. Colder water will take longer to heat up and come up to pressure, while hot water will take less time.

Additionally, when using a pressure cooker, always be cautious and take the necessary safety precautions to avoid any accidents.

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