Problem 27 Describe how changing the air pr... [FREE SOLUTION]

Chapter 5: Problem 27

Describe how changing the air pressure affects the temperature at which water boils.

Short Answer

Expert verified

Explain the concept and provide real-life implications. Answer: The boiling temperature of water changes with variations in air pressure due to the relationship between vapor pressure, atmospheric pressure, and phase change. When air pressure increases, the boiling temperature of water also increases, as the substance must be heated to a higher temperature for its vapor pressure to equal the increased atmospheric pressure. Conversely, when air pressure decreases, the boiling temperature of water decreases, as its vapor pressure will equal the decreased atmospheric pressure at a lower temperature. Real-life implications of this concept include the need to adjust cooking times at higher altitudes due to lower boiling temperatures and the decreased effectiveness of boiling water for sterilization purposes at high altitudes, as the lower boiling temperature is less effective at killing bacteria and other pathogens.

Step by step solution

Explain the relationship between pressure and temperature

At a given pressure, a substance will boil when its vapor pressure equals the atmospheric (air) pressure. The vapor pressure of a substance increases as the temperature increases. The boiling point of a substance is the temperature at which its vapor pressure equals the atmospheric pressure.

Explain the effect of increasing air pressure on boiling temperature

When the air pressure increases, the vapor pressure required for a substance to boil also increases. This means that the substance, in this case, water, must be heated to a higher temperature for its vapor pressure to equal the increased atmospheric pressure. Thus, the boiling temperature of water increases with an increase in air pressure.

Explain the effect of decreasing air pressure on boiling temperature

When the air pressure decreases, the vapor pressure required for a substance to boil also decreases. This means that the substance, in this case, water, will boil at a lower temperature because its vapor pressure will equal the decreased atmospheric pressure at a lower temperature. Thus, the boiling temperature of water decreases with a decrease in air pressure.

Real-life examples and implications

A common real-life example of this concept is that water boils at a lower temperature at higher altitudes, where the air pressure is lower. This can affect your cooking time when you are at high altitudes, as food may take longer to cook due to the lower boiling temperature of water. It also means that boiling water for sterilization purposes is less effective at high altitudes, as the lower boiling temperature is less effective at killing bacteria and other pathogens.

Conclusion

The boiling temperature of water is affected by changes in air pressure. As air pressure increases, the boiling temperature of water also increases, and as air pressure decreases, the boiling temperature of water decreases. This is due to the relationship between vapor pressure, atmospheric pressure, and phase change. Understanding this concept can help in various real-life situations, especially in cooking and sterilization processes.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor when it is in equilibrium with its liquid at a given temperature. It is a key factor in determining the boiling point of a liquid.

When a liquid heats up, its molecules gain kinetic energy and begin to transition into the vapor phase.
Vapor pressure increases with temperature because more molecules have enough energy to escape into the vapor phase.
The boiling point is reached when the vapor pressure equals the surrounding air pressure.

Understanding vapor pressure helps explain why water boils at different temperatures under varying pressures. At higher temperatures, vapor pressure rises, leading to eventual boiling when it surpasses air pressure.

Air Pressure

Air pressure, or atmospheric pressure, is the force exerted by the weight of the air above us at any given moment. It plays a crucial role in dictating the boiling points of liquids.

In areas with high air pressure, such as lower elevations, water boils at a higher temperature because it requires increased vapor pressure to match the stronger atmospheric pressure.
Conversely, in lower air pressure conditions, like high altitudes, water boils at a reduced temperature since its vapor pressure needs to equal the diminished atmospheric pressure.
This relationship between air pressure and boiling point is vital for understanding how pressure cookers work, utilizing higher pressure to raise the boiling point, thus cooking food faster.

Air pressure affects so many daily activities and industrial operations, especially those involving heat and phase change.

Phase Change

A phase change is the transformation from one state of matter to another, such as from liquid to gas. Boiling is a prime example of a phase change influenced by temperature and pressure.

During boiling, water molecules transition from the liquid phase to the gaseous phase.
This occurs when the energy in the water molecules is sufficient to overcome atmospheric pressure.
In regions of low air pressure, such as high altitudes, the phase change happens at lower temperatures since less energy is needed to surpass the pressure threshold.

Recognizing the principles of phase change is pivotal when cooking at different altitudes or adjusting recipes based on your environmental conditions.

High Altitude Cooking

High altitude cooking is an interesting phenomenon due to the reduced air pressure found in elevated areas like mountains. This reduced pressure results in several unique cooking considerations.

Because water boils at a lower temperature at high altitudes, it can lead to longer cooking times for certain foods, particularly for tasks like boiling eggs or cooking pasta.
Recipes may require adjustments; for instance, increasing cooking time or temperature might be necessary to achieve the same outcomes experienced at sea level.
For baking, leavening agents like baking powder and yeast may produce more expansive results, necessitating quantity adjustments.

Being aware of high altitude cooking implications helps when planning meals in mountainous regions and ensures safety and proper sterilization in these conditions.

91影视

Describe how changing the air pressure affects the temperature at which water boils.

Short Answer

Step by step solution

Explain the relationship between pressure and temperature

Explain the effect of increasing air pressure on boiling temperature

Explain the effect of decreasing air pressure on boiling temperature

Real-life examples and implications

Conclusion

Key Concepts

Vapor Pressure

Air Pressure

Phase Change

High Altitude Cooking

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