A camper pours 500 g of coffee, initially in a pot at 80 oC, into a 110-g aluminum cup initially at 30 oC. What is the final temperature? Assume that coffee has the same specific heat as water and that no heat is exchanged with the surroundings. (cwater=4.18 J/goC). (cAluminum=0.900J/g. C)

The final temperature : t=77.74 °C

Given

500 g coffee, t = 80 °C

110 g aluminum cup, t = 30 °C

Required

The final temperature

Solution

Q in = Q out

Q absorbed = Q released

Q aluminum cup = Q coffee

110 x 0.9 x (t-30)=500 x 4.18 x (80-t)

99t-2970=167200-2090t

2189t=170170

t=77.74 °C

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.