Chemical Collisions is one of a number of new titles from the Homerton college team headed by Fred Daly. We reviewed Tesselations back in December and will be looking at other titles next month.

The significant difference from other educational packages displayed by the Homerton software is the emphasis on the man/machine interface. Chemical Collisions makes use of the extremely clever and effective method employed in Tesselations. The relevant initial letters of the available functions are displayed in the bottom right hand corner of the screen. The cursor keys move along with this row of letters, the Return key selecting the one required. A further sub-menu is then displayed. The space bar gets you back to the last menu in the hierarchy.

The Cambridge Micro documentation is its usual excellent self but to be honest, someone new to the program could probably find out, by deduction, how to operate the software without documentation. It is that user-friendly.

Chemical Collisions itself is designed to display the random collisions at the atomic and molecular level, collisions which lead to chemical change. The documentation goes into various paths which might be followed in the classroom, with observation leading to conclusions based on the graphical output provided by the program.

The Screen display is devoted to status information at the top and two windows. The left hand window is the container around which the particles move. The right hand contains the graphical output, either line or bar charts. The various plots can be displayed in any combination allowing the teacher to make a point of comparison.

The initial number of particles in each half of the container is chosen and the temperature can be controlled from the menu. The particles are set in motion and are mixed by hitting space bar. Collisions are signalled visually and aurally (although the options are changeable) and are mapped out on the graphical display.

Other nice features are the ability to centre the position of the display on your screen and to redefine the colours used within the main program. The function keys can also be used to "remember" combinations of display options for future use and reference. It is unfortunate that the graphical displays cannot be dumped to a printer for analysis away from the computer. Apart from this small deficiency, Chemical Collisions is a real resource for the Chemistry classroom.