Do you know Why is it hard to make Tea on a Mountain? You know that there is more to making a really good cup of tea than just pouring hot water onto a few tea leaves and then pouring it out. The next time your mother makes tea, watch. You will find that she puts the kettle on the heat, and before the water boils she puts a little into the teapot to warm it.
She will then dry the pot, carefully put in the correct amount of tea, and when the water is boiling hard she will take the post the kettle before purring in the water. Why does she go to all this trouble for a cup of tea?
The answer is that you simply cannot make tea if the water is not at a temperature of 100°C, that is, under normal conditions when the water is boiling. But what is the connection with making tea on mountains?
To understand this, you must know what is meant by boiling. All liquids release a certain amount of vapor. This vapor exerts a pressure; that is, it pushes on its surroundings. As a liquid is heated, the pressure increases until eventually, it is the same as the pressure of this is the boiling point.
What is air pressure? We do not feel the air pressing down on us. But in fact, every square centimeter of the Earth’s surface at sea-level feels an air pressure of about one kilogram. This is really the weight of a column of air measuring one centimeter by one centimeter by the height of the column.
And that is quite a lot of air!
What happens when you climb a mountain? Obviously, the column of air becomes shorter and the pressure of the air is reduced. For example, if you were to climb to a height of 6000 meters, the air pressure is about half the air pressure that you would feel at sea-level.
If you try to make tea at this height you will find that because the air pressure is lower, the pressure of the water will be lower when the water boils and it will not be so hot. You cannot make the water any hotter because it simply turns into steam. This all lead to a rather poor cup of tea!
If you have watched the weather forecast on television you will have seen that the forecaster charts have lots of lines on them the air pressure along any one line or isobar as it is called is exactly the same but different lines indicate different pressures.
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