Chemistry Question

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charlotteduckett | 16:35 Wed 01st May 2019 | Science
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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.

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