Learn why wet sand turns into hard, crumbly blocks as it dries, explained in simple terms for children around 11 years old.
When sand is wet, water fills the spaces between the tiny grains of sand. This water acts like a glue, holding the grains together. Wet sand feels soft and moldable because the water helps the grains stick to each other.
As the sand dries, the water starts to evaporate — that means it changes from liquid to gas and disappears into the air. Without enough water, the 'glue' that held the grains together gets weaker. So, the sand can't hold as tightly, and the grains begin to come loose.
At first, the sand might seem hard because the grains are packed closely without water, but since it's drying, the sand becomes crumbly and breaks apart easily. This is why dry sand feels hard but can crumble into small blocks or pieces.
To sum it up: water between sand grains holds them together when wet. When the water dries up, the sand loses that stickiness and turns into hard, crumbly blocks.