Explain the cooling effect experienced when ethanol is rubbed on your skin, given that
C2H5OH (l) ----> C2H5OH (g) dH = 42.4 kJ/mol
2006-11-01 13:49:39 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
sweet, i have this textbook. THere's a cooling effect because the reaction is endothermic. When the ethanol is rubbed on your skin, it vaporizes, and because the reaction is exothermic the energy is drawn from your skin which is why you experience the cooling effect
2006-11-01 13:52:31 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Well basically, this reaction is endothermic, meaning that it requires energy to actually take place. Here we are subtly told that it is endothermic based on the dH given, a positive dH means endothermic, where negative means exothermic.
In endothermic reactions the reactants (in this case C2H5OH (l)) need energy in order to be converted to C2H5OH (g). The product however does not need energy, and does not give off energy, which explains the cooling effect. As heat is required (which can be obtained from body heat when ethanol is rubbed on the skin) the end product becomes cooler.
Hope this helps!
2006-11-01 21:57:30 · answer #2 · answered by meg2165 1 · 0⤊ 0⤋
The equation simply shows that ethanol is evaporating, not reacting. Evaporation is an endothermic change which absorbs heat.
So ethanol is absorbing heat from your skin.
2006-11-01 21:53:37 · answer #3 · answered by Kiri 4 · 0⤊ 0⤋
well, its just latent heat. for something to evaporate, it needs some heat to change from liquid to gas. and ethanol has a pretty low boiling point of about 70+C. so when the ethanol evaporates, it takes its heat for evaporation from your skin, thereby making your skin feel cooler.
water also can make yuor skin feel cool when it evaporates, but its harder to evaporate as its boiling point is about 100C
2006-11-01 21:54:41 · answer #4 · answered by Q 2 · 0⤊ 0⤋