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Chemistry Question
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You have a cup of tea (250 mL) that is 375 K which is too hot to drink. It needs to be cooled to 350 K before you can drink it. How much thermal energy has to be transferred from the tea to the surroundings to cool the tea?
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First off, at 375K you are being overcharged for your tea.
Clearly you need to lose 25 degrees Kelvin from a quarter of a litre, or 100K from a litre. At 9.88 litres per second squared, this is 97.61 litres/Kelvin per second, or 17.57 kilolitres Kelvin in three minutes, the time I leave my tea to cool down.
Assuming standard temperature and pressure, and a reasonable sized mug (not one of those Sports Direct ones), and with a conversion rate of x9/5 + 32 (Celsius to Fahrenheit) and then multiplied by Fletcher's Constant, you will need to shed 63.6 kJ of thermal energy.
Or you could add milk or cold water much quicker.
Clearly you need to lose 25 degrees Kelvin from a quarter of a litre, or 100K from a litre. At 9.88 litres per second squared, this is 97.61 litres/Kelvin per second, or 17.57 kilolitres Kelvin in three minutes, the time I leave my tea to cool down.
Assuming standard temperature and pressure, and a reasonable sized mug (not one of those Sports Direct ones), and with a conversion rate of x9/5 + 32 (Celsius to Fahrenheit) and then multiplied by Fletcher's Constant, you will need to shed 63.6 kJ of thermal energy.
Or you could add milk or cold water much quicker.
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