# Liquid temperature under pressure

• Scott jones
In summary, the conversation is about pasteurizing cider in bottles at a temperature of 70 degrees Celsius. The person uses a test bottle with a cork to monitor the temperature and is wondering if the temperature inside the capped bottle rises at the same rate as the test bottle due to being sealed under pressure. The person notes that the capped bottles do expand into the neck space. It is mentioned that the heat capacity and thermal conductivity of water should not be affected by pressure, but the chemical composition may have an impact.
Scott jones
Hello,
I have a question regarding bath pasteurising cider in bottles.
The bottles are carbonated with CO2 and capped, I heat the water up to a temperature of 70deg.C
I use a test bottle filled with water and with a cork in the top, I use this to monitor the temperature inside the bottle.
So my question is about the capped bottle temperature vs the corked test bottle temperature.
Do they rise at the same rate or does the capped bottle have a higher increase due to being sealed under pressure, I constantly take the cork out to take a temperature reading so the water isn't under any pressure.
The capped bottles do expand into the neck space quite considerably, so the bottle is under pressure.

The heat capacity and thermal conductivity of water shouldn't depend notably on the pressure (for reasonable pressure values).
The different chemical composition might have an impact.

## 1. What is the relationship between liquid temperature and pressure?

The relationship between liquid temperature and pressure is known as the Clausius-Clapeyron equation, which states that as pressure increases, the boiling point of a liquid also increases. This means that at higher pressures, liquids require a higher temperature to reach their boiling point, and at lower pressures, they require a lower temperature.

## 2. How does pressure affect the freezing point of a liquid?

Pressure has a similar effect on the freezing point of a liquid as it does on the boiling point. As pressure increases, the freezing point of a liquid also increases, meaning that it requires a lower temperature to freeze. On the other hand, at lower pressures, the freezing point decreases, and the liquid may remain in a liquid state at temperatures below its normal freezing point.

## 3. Can a liquid's temperature increase indefinitely under pressure?

No, a liquid's temperature cannot increase indefinitely under pressure. At some point, the liquid will reach its critical temperature, which is the highest temperature at which it can exist as a liquid. Beyond this point, the liquid will become a gas, regardless of the pressure applied.

## 4. How does the type of liquid affect its response to pressure and temperature?

The type of liquid can greatly affect its response to pressure and temperature. Some liquids, such as water, have a relatively high boiling point and freezing point, meaning they require a lot of pressure to reach their critical temperature. Other liquids, like alcohol, have lower boiling and freezing points, making them easier to manipulate under pressure and temperature changes.

## 5. What are the practical applications of understanding liquid temperature under pressure?

Understanding liquid temperature under pressure is crucial in many industries, such as food processing, pharmaceuticals, and chemical engineering. It allows for the precise control of liquid properties, such as boiling and freezing points, which is necessary for the production of certain products. It also helps in the design and maintenance of equipment that handles liquids under high pressure conditions.

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