I recently purchased this balance scale from Haba toys. I have been wanting one for awhile. I liked this scale because the dishes are removable and because they are metal. For now, it is used with solids, but I will introduce liquids later. I imagine someday it might be used to settle a "she has more" sibling food dispute.
After modeling how the balance works and experimenting with it for a bit, we started with this activity. One person filled one bowl as much or as little as desired. I had an assortment of solid objects to choose from.
The other person then filled the other bowl (one object at a time) until it was balanced.
Another activity we did was to each fill our own bowl...
and then see if we could feel which one was heavier, moving our arms like a balance.
We then tested them on the balance to see if we were correct.