3.4
3.4.1
A cup of tea on Everest
Introduction
In this section we continue to investigate the phenomena of phase change. The concept of ‘boiling point’ is very common, we shall now learn how the apparent boiling point of a liquid varies with pressure.
Terms
Be able toBy the end of this section you should be familiar with terms such as:
Boiling point
Saturation temperature and pressure
Critical temperature and pressure
Use a phase diagram to estimate change in boiling point with pressure
3.4.3
A cup of tea on Everest
Pause for thought
Water boiling tempretures on Mount Everest
2850m - 95°C
3985m - 91°C
4300m - 88°C
Base Camp - 5365m - 79°C
Summit - 8848m - 69°C
In the video we saw the real effect of altitude on the temperature of boiling water, as altitude increases so the boiling point reduces.
What about in the opposite direction, as pressure increases what happens ?
Are there any limits, either increasing or decreasing pressure?
Do you think this will continue indefinitely?
3.4.4
A cup of tea on Everest
Screencast
Outline
In this unit we will continue to investigate the phenomena of liquid to vapour phase change. The term “boiling point” is very common and we will explore further what this implies.
We will review the concept of saturation temperature, commonly referred to as the boiling point and then explore how saturation temperature varies with pressure.
3.4.5
A cup of tea on Everest
Review Questions
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Referring to the material presented in this section, can you answer the following questions -
Does the temperature change during a constant pressure phase change from liquid to vapour?
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Referring to the material presented in this section, can you answer the following questions -
What is the formal name for temperature and pressure during phase change?
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Referring to the material presented in this section, can you answer the following questions -
What is the formal definition of the “Boiling Point” of a liquid?
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Referring to the material presented in this section, can you answer the following questions -
How does the boiling point of a liquid vary with pressure?
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Referring to the material presented in this section, can you answer the following questions -
What type of cooking vessel might be used to offset the effects of altitude?
