A) A student is sitting in the sun reading for his exam. He brought a bottle con
ID: 985124 • Letter: A
Question
A)
A student is sitting in the sun reading for his exam. He brought a bottle containing 1,00L of water. After 2 hours the temperature of the water has increased from 4°C to 20°C. During this time the sun/suroundings has applied -66,90 kJ to the water. Assume the volume of 1,00kg of water is 1,00L and calculate the waters heat capacity.
B)
The student from A) want to cool his water and adds icecubes to the water. How many 0°C icecubes wheighing 5g does he have to add to cool the water back down to 4°C?
Explanation / Answer
A)
heat applied = Q = - 66,90 kJ
temperature increase from = 4 to 20oC
mass of water = 100 kg
Q = m Cp dT
6690 x 10^3 = 100 x 10^3 x Cp x (20 - 4)
Cp = 4.18 J/goC
heat capacity of water = Cp = 4.18 J/goC
B)
Q = m Cp dT
here the concept is
heat loss by water = heat gained by ice
100 x 10^3 x 4.18 x (20 - 4) = m x 2.01 x (4 - 0) + m x 335
m = 19498.5 g
each one having 5 g.
so number of ice cubes = 3900