Question

You will now test the porosity (the space between the particles) of the soil. You'll compare the porosity of the soil with the porosity of sand and pebbles by measuring how much water fits in a glass with the same amount of each material. Note that the sand will be made up of a combination of fine and coarse sand particles. All of the pebbles, on the other hand, will be of roughly equal sizes. Set three identical glasses on the counter or table. Put the half cup of sand in one glass, the half cup of pebbles in the second glass, and a half cup of your soil sample in the third glass. Make a prediction about how much water can fit in each glass. Which sample will hold the most water? Write down your predictions on the porosity of all three samples.

Answer 1

Based on their particle size and pore structure, I predict the following order for water-holding capacity (from highest to lowest):

Sand

Soil

Pebbles

I predict that sand will hold the most water. Sand particles are much smaller than soil particles and pebbles, leaving more space between them for water to occupy. Additionally, the combination of fine and coarse sand creates a wider range of pore sizes, allowing for even more water retention.

I predict that soil will hold less water than sand but more than pebbles. Soil particles are a mix of different sizes, creating some pore space for water. However, organic matter and finer clay particles within the soil can fill some of those pores, reducing the overall water-holding capacity.