Final answer:
The best description of the first law of thermodynamics as applied to the melting and freezing of wax in a test tube is option a: 'The total energy lost by the wax and test tube is equal to the total energy absorbed by the surroundings.' This reflects energy conservation during heat transfer.
Step-by-step explanation:
The first law of thermodynamics, also known as the conservation of energy principle, applies to the experiment involving wax melting and freezing in a test tube. According to this law, the change in internal energy of a closed system (ΔU) is equal to the net heat transfer into the system (Q) minus the net work done by the system (W), expressed as ΔU = Q - W. When the test tube containing wax is warmed, it gains thermal energy from the oil bath, which leads to the melting of the wax. Upon removal and cooling, the wax releases thermal energy to the surroundings as it freezes.
Statement a, 'The total energy lost by the wax and test tube is equal to the total energy absorbed by the surroundings,' most accurately describes the first law of thermodynamics in this context. It reflects the principle that the energy is conserved in the process of heat transfer. The total amount of energy does not change; instead, it is transferred from the wax and test tube to the surroundings during cooling and solidification.
That being said, the notion described in option b, which states that 'Thermal energy flows from the wax and test tube to the surroundings, but not in the reverse direction,' is supported by the second law of thermodynamics. This law addresses the direction of spontaneous processes, indicating that heat flows from hotter to cooler objects.