How much does it weigh?

We have been finding out about how much things weigh. We looked at home in our pantries and found foods that weigh more than 1 kilogram and less than 1 kilogram. We looked on the packets and boxes and found the weights in grams and kilograms.
Next we looked at two shopping bags that looked the same. We asked the questions:
Are they different or the same?
How do we know?
What can we do to find out?
When we lifted the bags we found out that one bag was heavy and contained some books.
We have been weighing different object in the classroom to make them balance with cubes. It has been fun trying to find out how many cubes it takes to balance things.