<p>Viscosities of water, different aqueous compositions of maltose and lactose were measured before and after the addition of copper (II) sulfate (CuSO₄.5H₂O) at 303.15–323.15&#xa0;K. The viscosity of water increased with the addition of copper (II) sulfate, maltose, and lactose, while it decreased with the rise in temperature. The relative and specific viscosity data fitted well into the Jones-Dole, Vand, Moulik, and Einstein relationships, whereas relatively low correlation coefficients were observed for the Thomas relationship. Jones-Dole, Vand, and Breslau-Miller equations were utilized to evaluate the B-coefficients, whereas the structure-making/breaking property of CuSO₄ was evaluated by analyzing its trend concerning temperature. A positive value of dB/dT in water and aqueous maltose characterized CuSO₄ as a structure-breaker, whereas a structure-making conduct was observed in aqueous lactose. The ionic B-coefficients, D-coefficient, B-coefficients of transfer (Δ_tB), activation energy (E_a), and thermodynamic parameters of the viscous flow and ion-solvation process were also evaluated.</p> Graphical abstract <p></p>