The balance question

We have a simple balance with us. No distortions; analogous to the good old unbiased coin of the bad old questions of probability that you might have solved in your std 12th.

We place 1 kg mass on the one scale and 1/2 a kg mass on the other. The former scale (heavy with its greatness, as a branch full of fruits) goes down lifting the latter scale. Fine? Now we put another 1/2 a kg mass on the second scale, without giving any jerk, any impact, we observe that it comes down (with its newly acquired humility) lifting the first one.

I'm sure each one of us has seen this phenomenon many times. A balance is a very useful and very popular instrument and its ability to balance is so much appreciated that it is accepted as a symbol of justice. But lets chuck philosophy for a while and return to the world of physics. Have you ever wondered why this happens? Why does the first balance comes up and the second balance goes down when we keep the weight on the second one?

This is an interesting question and you can try to solve it.

Try to make a diagram when you put the 1/2 kg weight at the second scale. We see that there are two mutually cancelling torques about the hinge, so we dont have a net torque.

Also, the total potential energy of the system also remains the same(gained by the first and lost by the second).

Any answers?