As the season progresses the time of sunrise and sunset changes but why is the change in time unequal eg sunrise may change by 2 minutes but sunset may change by only 1 minute?

A lot of this is just due to rounding. Most sunrise/sunset tables are in whole minutes, so the changes are pretty choppy. But there is an astronomical reason. If the earth's orbit were a perfect circle, we would see the same change in sunrise and sunset every day. For example, on a given day in the fall, sunrise would be 90 seconds later than the day before, and sunset would be 90 seconds earlier. But it's not a circle, it's slightly elliptical, so the speed we move around the sun changes throughout the year. This causes solar time to be a little off from clock time, and by a different amount each day. This is reflected in the analemma, the figure-8 thingy often found on globes. Also try searching on that word, and you will find a bunch of interesting stuff.