The transient hot-wire technique is re-investigated in order to measure, simultaneously and accurately, the thermal conductivity λ and thermal diffusivity κ of a liquid. Newly derived effective temperatures T_λ and T_κ that are associated with the measured values of the thermal conductivity and thermal diffusivity are introduced and replace the previously used temperatures T₀ and T_m. Higher-order corrections due to the thermal properties of the wire material are also re-investigated; these may be significant for experiments on lower-density substances or when using a hot-wire sensor with a thicker wire. The radiation (photons) emitted from or absorbed into the medium is discussed, and its contribution is taken to be part of the ordinary heat-conduction phenomenon exhibited by carriers such as phonons, electrons and molecules. The new system was tested by measuring the thermal conductivity and thermal diffusivity of n-heptane, n-pentane and iso-pentane, and values for their volumic heat capacities were calculated from the ratios λ/κ. The relative combined expanded uncertainties of the measured values (coverage factor k = 2) were 0.38 % for λ, and 1.7 % for κ and c_pρ.