Experimental data over the temperature range from (263 to 365) K are presented on the 0.1 MPa density and air-liquid surface tension for 1-C-n-3-methylimidazolium tetrafluoroborates with n = 3, 5, 7, 9, 10 and 12, still poorly or even not studied in these respects at all. The reported density data were obtained using a single-sinker buoyancy method with an estimated combined expanded uncertainty at 0.95 confidence level U-c not exceeding 0.6 kg.m(-3) (6 . 10(-4)rho). The surface tension data were obtained by the Wilhelmy plate method with U-c from 0.04 to 0.12 mN.m(-1) for n = 3 and n = 12, respectively, and by du Nouy ring method with Uc from 0.17 to 0.8 mN.m(-1). The Kruss K100 Mk2 tensiometer was used to determine the buoyancy and surface tension forces. The new data allowed to identify the most credible density and surface tension values for 1-C-n-3-methylimidazolium tetrafluoroborates with n = 2, 4, 6, and 8. Empirical models rooted in group contribution and parachor concept are reported, generating recommended values for the 0.1 MPa density and the surface tension for members of the studied homologous series. The worst-case error of the recommended values of the density and surface tension are estimated to 0.1% and 0.3 mN.m(-1), respectively. (C) 2016 Elsevier Ltd. All rights reserved.