The rise of mobile computing has changed the complete landscape of our day to day life and the way software is developed and used. Apart from the traditional Personal Computers, there are portable devices such as tablets and smartphones which can be used to access the same software. All these smartphones and tablets comes with different platforms such as Android, iOS, windows. An application that supports multiple platforms reaches a wider audience. Cross-platform software may be divided into two types; one requires individual building or compilation for each platform that it supports, and the other one is to build a mobile interface based on web technologies that can be accessed through a web browser and can run on any platform. TEST, The Expert System for Thermodynamics, is a courseware created to analyze engineering problems and solutions. Applications in TEST are mainly desktop based, and cannot be accessed from mobile devices. Given the widespread use of smartphones and tablets today, there is a need to make the applications accessible from mobile devices. A widely used analysis tool in TEST called the Gas Model. Using this tool, one can calculate the thermodynamic properties of gases. This thesis attempts to build a mobile web interface for the Gas model that can be accessed from multiple mobile platforms. In building this interface, we have adopted a client-server model of computing. The complex thermodynamic calculations have been separated into a web service. This web service will be invoked by the mobile web application