Which of the following absorbs water best and why? Flour, salt, sand
Ciaran Dowling from Northamptonshire (Aged 5-14)
Filed under: age 5-14, Answered Big Questions, Chemistry Big Questions
Which of the following absorbs water best and why?
Posted on March 14, 2008 by joannarooke
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Hi Young Scientist
.
A material like common (table) salt absorbs water faster than flour. Sand will not absorb water at all. The ability of a material to absorb water depends on the chemical nature of that material in comparison to the chemical nature of water. A way of picturing this is to consider a sponge that you might use in your bath and a stone or a pebble, both placed in a bowl of water. The sponge is made very light for it’s size because the chemical nature of sponge is of ‘low density’ and the air pockets or ‘cells’ of which a sponge is composed produce a large structure which is mainly spaces (filled with air when the sponge is dry). The stone is very heavy for its size because the chemical nature of these little rocks is of ‘high density’ with no big spaces between the tiny particles from which it is made. The sponge absorbs water very easily and all the spaces quickly fill up. The stone does not absorb water at all. Lift them both out of the bowl and you will realise that the sponge hangs onto most of the water that it has absorbed (so it is much heavier than when dry) but the stone is just the same weight (ignore the wet on the stone’s surface as this was not ‘absorbed’). A similar difference to this exists, to various extents, between other materials and thus dictates their ability to absorb water.
I hope this answer helps to explain how some materials can absorb water more easily than others.
Good Luck,
Rockno3.