How heavy is it?

This week we have been learning about how heavy objects are by firstly hefting, then using the balancing scales. Early in the week we made two play-dough echidnas with equal mass which we checked by using the scales. Then we added match sticks to one of our echidnas to see what would happen. We discussed which is heavier, why and what happens to the scale when something weighs more. Then later this week we conducted another investigation in which students had to predict whether a cup of sand or a cup of rice would be heavier. Most of us said "rice because it's bigger" but after a few trials every group found that a cup of sand was heavier and had the greatest mass. In the end we established that sand was denser and that is why it was heavier.