Garden Mulch Packers: Track the Whole Weight

Preparing Leaf Mulch

At the school garden's leaf-mulch packing station, students prepare damp leaf mixtures for a ground-cover demonstration. They use clean fallen leaves collected by an adult and room-temperature water. They wear gardening gloves and wash their hands afterward. Their question is whether mixing, crumbling, or draining materials changes the total weight of the matter they are tracking.

The students place a digital scale on a level bench and check that its empty platform reads zero. They record readings in grams after the display settles. For each mixing trial, they first weigh the dry equipment together: a plastic tub, its lid, and a small inner cup. They measure the leaves and water separately, using the scale's reset button to leave out the weight of temporary measuring dishes.

Next, they put the leaves in the tub and the water in the inner cup. The cup stands inside the tub, keeping the water separate from the leaves. They close the lid and weigh the whole setup before mixing. Then they gently tip the closed tub so the water leaves the inner cup and wets the leaves. They turn the tub several times and weigh it again. The same tub, lid, cup, leaves, and water remain together. Nothing enters or leaves.

For a draining test, the students put a fresh damp leaf mixture in a strainer basket resting inside a catch bowl. They weigh the basket, bowl, and mixture together. They lift the basket and hold it above the bowl while water drains into the bowl. No water spills. They then weigh the basket and bowl together again, with the basket resting inside the bowl as before. Finally, they weigh the basket with its wet leaves and the bowl with its collected water separately. The graph later on this sheet gives these measurements.

The students also test a sealed pouch containing dry leaves. The pouch and leaves weigh 68 g. They gently crumble the leaves through the pouch without opening it. The pieces become smaller, and the closed pouch still weighs 68 g. They record both the changed appearance and the scale readings rather than judging weight by how much space the leaves seem to fill.