According to the first law of thermodynamics, if the internal energy increases, it implies that heat is added to the system and/or work is done on the system.

According to the first law of thermodynamics, if the internal energy increases, it implies that either work is done on the system or heat is added to the system.

The efficiency of a Carnot engine is determined by the temperatures of both the hot and cold reservoirs, given by the formula η = 1 - (T_c/T_h).

The heat capacity at constant volume (C_v) is defined as the amount of heat added to the system divided by the change in temperature at constant volume.

The specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kg of the substance by 1°C.

The specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kg of the substance by 1 degree Celsius.

The work done by an ideal gas during an isothermal expansion is given by W = nRT ln(Vf/Vi), where Vf and Vi are the final and initial volumes.

The heat required to change a substance from solid to liquid at its melting point is called the latent heat of fusion.

The heat required to change a substance from solid to liquid at constant temperature is called the latent heat of fusion.

The work done by an ideal gas during an isobaric (constant pressure) expansion is given by W = PΔV.

The second law of thermodynamics states that the entropy of an isolated system will always increase over time.

The second law of thermodynamics states that the entropy of an isolated system never decreases over time.

An ideal gas is considered to have no volume and no intermolecular forces, making option D correct.