More AP Chem help needed. :)

Question

A snowball at -15 degrees Celsius is thrown at a large tree trunk. If we disregard all frictional heat loss, at what speed mus the snowball travel so as to melt the snowball on impact? (Show all work) Thanks

Answer 1

Do your own d**n homework.

Answer 2

That means that all of the kinetic energy of the snowball is going to be converted to thermal energy and stay in the snowball because as everyone knows tree trunks are thermal insulators.

To melt the snowball you must know its mass or solve for the heat in terms of m.  For all of the concrete thinkers (Piaget) out there, assume a 1kg snowball.

Q = mcDT(ice) + mDHfus

Look up the specific heat of solid water and the heat of fusion of ice, and compute Q.  That will be the heat needed to bring the snowball to zero C and then melt it at zero C.

That will be equal to the kinetic energy of the snowball (again, assuming no heat is transferred to the tree).

KE = 1/2mV^2

KE = Q

Q = 1/2mV^2

V = (2Q/1 kg)^(1/2)

And don't forget the correct units.  Since energy is in joules and the mass in kg, then speed (velocity) will be in m/s.