For break arcs occurring between Ag and Ag/SnO₂ 12 wt% electrical contact pairs, the electrical conductivity, viscosity and specific heat at constant pressure are calculated as thermodynamic and transport properties. Mixture rates of contact material vapor are 0%, 1%, 10% and 100%. Influence of the contact material on the properties is investigated. Temperature for the calculation ranges from 2000 K to 20000 K. Following results are shown. When the mixture rate is changed, the electrical conductivity varies at lower temperature ( < 10000 K), and the viscosity and specific heat vary widely at all temperature range. The electrical conductivity is independent of the mixture rate when the temperature is exceeding 10000 K. The thermodynamic and transport properties are independent of the kind of the contact materials.