Copper oxide nanoparticles are used in the synthesis of CuO nanofluids for increasing the thermal conductivity of nanofluids. The method of preparation of nanofluids in stable form is of much significant in the field of nanofluid and its application. In this present work, CuO nanoparticles (particle size: 40 nm) are dispersed in double distilled water and nanofluids are prepared at ten different concentration (0.2% - 2.0%) in steps of 0.2 at room temperature. Viscosity studies are carried out at different temperatures (303K, 308K, 313K __ampersandsignamp; 318K) for the prepared nanofluids. From the experimental values, the activation energy is calculated and ultrasonic velocity, density, refractive index and thermal conductivity studies are performed at room temperature. Various molecular interaction parameters are determined to analyze the nature of molecular interaction in the sample taken for study.