Answer:
(a)
Energy moves from the surroundings to the wax.
(b)
Q = 2.62 KJ
(c)
The density of a substance is characterized by the number of particles it contains per unit volume. When melting occurs, the intermolecular forces and bonds between the molecules or atoms weaken. This process leads to an increased distance between these particles. Consequently, the number of particles per unit volume diminishes, which reduces the density of the substance.
Explanation:
(a)
During melting, the solid substance needs energy to break bonds between its molecules or atoms.
So, while wax melts, the net thermal energy flows from the surroundings into the wax.
(b)
The energy needed to melt solid paraffin wax is defined by the equation:
Q = nC
where,
Q = energy quantity
C = Molar Heat of Fusion = 48.78 KJ/mol
n = number of moles = Mass in grams / Molar Mass = (15.2 g)/(282.62 g/mol)
n = 0.0538 mol
Thus,
Q = (0.0538 mol)(48.78 KJ/mol)
Q = 2.62 KJ
(c)
The density of a substance is defined as the number of particles packed in a unit volume. As the substance melts, the attractive forces between its molecules weaken. This results in an increase in separation between the molecules or atoms. Consequently, the number of particles in a unit volume is reduced, leading to a decrease in the substance's density.
