A student is preparing 250 cm3 of coffee at 85 deg cel in a cup
. Given:
Mass of 1 cm3 of coffee/milk = 1 g
Specific heat capacity of milk = 4800J/kg del cel
Specific heat capacity of coffee = 4200J/kg deg cel
Specific heat capacity of copper = 370 J/kg del cel
(i) When she add 50cm3 of milk at 5 deg cel to the coffee what
is the final temperature of the coffee? My answer: 70.1 del cel
(ii) She then stirs the coffee with a 100g copper
teaspoon at 20 deg cel. What is the temperature of the coffee after
she stirs the coffee? (you may ignore any thermal energy transfer
between the hand and the teaspoon)
Not sure how to do this.
Is it,
Energy gained by copper teaspoon = Energy lost by coffee+
Energy lost by milk
Do I have to take into account the energy lost by milk? And in
any case, when you want to find the energy lost by coffee, you have
to know its temperature change. So is temperature of 20 deg cel in
the question referring to coffee+milk at 20 deg cel or do I use the
70.1 deg cel (ans found in part(i)) earlier on in the
question? Cuz i have to know the intial temperature before
being able to subtract or add the final temperature to my
equation.
(iii) Some people prefer to add sugar before milk. Can you
suggest a reason for that? Why don't they do it the other way
round?
Quite a lame question but no solid answer from me. Sugar can
dissolve faster?
thanks