As a person pushes a box across a for the energy from the person's moving arm is transferred to the box, and the box
and for become warm during this process, energy is
increased
conserved
destroyed
decreased
created

(a)

From surrounding to wax

(b)

Q = 2.62 KJ

(c)

Density of a substance is defined as the no. of particles of the substance, that occur in a unit volume. So, when the substance melts, the inter-molecular attractive forces and bonds between molecules or atoms are weakened. This, increases the distance between the molecules or atoms. Hence, the no. of particles in a unit volume is decreased. As, a result of this, the density of the substance also decreases.

Explanation:

(a)

During the melting process, the solid material or substance requires energy, in order to break the bonds between its molecules or atoms.

Therefore, while the wax is melting, the net flow of thermal energy is from surrounding to the wax.

(b)

The amount of energy required to melt solid paraffin wax is given by the formula:

Q = nC

where,

Q = amount of energy

C = Molar Heat of Fusion = 48.78 KJ/mol

n = No. of Moles = Mass in gram/Molar Mass = (15.2 g)/(282.62 g/mol)

n = 0.0538 mol

Therefore,

Q = (0.0538 mol)(48.78 KJ/mol)

Q = 2.62 KJ

(c)

Density of a substance is defined as the no. of particles of the substance, that occur in a unit volume. So, when the substance melts, the inter-molecular attractive forces and bonds between molecules or atoms are weakened. This, increases the distance between the molecules or atoms. Hence, the no. of particles in a unit volume is decreased. As, a result of this, the density of the substance also decreases.