Why do we sweat

We all sweat at some time or other, e.g. after running hard, living in a hot climate or perhaps during an illness when our temperature is raised due to an infection (which is why we sometimes say, we have got a temperature ). 

Producing sweat is one of the body s natural ways of cooling itself, and it operates as follows. Sweat is an aqueous solution of salt and natural oils, and is secreted by glands just below the surface of the skin. The glands generate this mixture whenever the body feels too hot. Every time air moves over a sweaty limb, from a mechanical fan or natural breeze, the skin feels cooler following evaporation of water from the sweat. 

We need the salt in sweat to decrease the water s surface tension in order to speed up the evaporation process (we feel cooler more quickly). The oils in sweat prevents the skin from drying out, which would make it susceptible to sunburn. 

A process is endothermic if the final state has more energy than does the initial state. The word derives from the Greek roots thermo (meaning energy or temperature ) and endo (meaning inside or within ). An endothermic process takes in energy. 

Worked Example 3.2 What is the change in internal energy during sweating  

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