Investigating which rock is most permeable
Chemistry · Key Stage 2 · The School
What permeable means
A PERMEABLE rock lets water pass through it. A rock that does not is called NON-PERMEABLE. Chalk and sandstone are permeable. Granite and slate are not. You cannot always tell just by looking, so you test it.
Planning a fair test
To compare rocks fairly, use pieces of a similar size. Drip the same number of drops of water onto each one, from the same height. Time how long the water takes to soak in, or weigh the rock before and after. Change only the rock. Keep everything else the same.
Running the test
Place chalk, sandstone, granite and slate on separate trays. Drip ten drops of water onto each, one at a time, and start a timer. Chalk and sandstone soak the water in within seconds. Granite and slate leave the water sitting on the surface, because it has nowhere to go.
What the results show
The results sort neatly into two groups: fast-soaking rocks and rocks the water sits on. That grouping matches which rocks are used to build things that must stay dry, like slate roofs, and which are used where water passing through does not matter. A test with a clear yes-or-no result, like this one, is exactly the kind that makes a good scientific investigation.