Question: A pressure cooker contains water and steam in equilibrium at a pressure greater than atmospheric pressure. How does this greater pressure increase cooking speed?
A pressure cooker increases cooking speed by increasing the temperature. It contains water and steam in equilibrium at a pressure greater than atmospheric pressure. According to the ideal gas law, as the pressure increases, the temperature also increases. As the pressure inside the pressure cooker increases as it is heated, the temperature also increases.
If we heat a liquid, the average Kinetic Energy of the liquid increases and at a particular stage, the energy becomes sufficient to break the molecular attraction. The molecules in the liquid can form vapor bubbles. These bubbles float to the surface of the liquid and finally come out of the liquid. This phenomenon is called boiling and the temperature at which it occurs is known as the boiling point.
The boiling point of a liquid depends on the external pressure over its surface. When the pressure decreases, the boiling point decreases. That`s why at places with high altitudes, water will boil before reaching .
A pressure cooker is a sealed pot with a valve that controls the steam pressure inside. As the pot heats, the liquid inside forms steam, which raises the pressure in the pot. This enables us to cook at a higher temperature, making the process faster.
Therefore, the pressure inside the pressure cooker increases as it heats up, then the temperature also increases.
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