There’s metal in your salt: a soft
grey metal you could cut with a knife,
that, dropped in water, flares aloft
and fizzes, hissing into life.
And there’s a gas in it as well,
a yellow-green and poisonous cloud,
with bleach’s sharp and stinging smell,
that sets you coughing, long and loud.
The sodium has one to spare,
a lone electron, loosely held;
the chlorine’s one short; so the pair
make one exchange, and both are quelled.
And after that, they’re charged, the two,
one plus, one minus, so they cling
and stack in rows, as charges do:
a cube of crystal, glittering.
Each ion’s ringed by six, all round,
of the other kind, on every side,
so firmly that the cube stays sound
till past eight hundred it’s been fried.
And all the danger’s gone away:
no fizz, no flame, no choking air,
just something white you eat each day
and shake on chips without a care.
It’s not the parts that make the thing,
it’s how they’re joined. Join two that harm,
and, held in one electric ring,
they turn to dinner, safe and calm.
A small experimentGrow salt cubes
- Stir salt into the warm water a spoonful at a time until no more will dissolve.
- Pour a thin layer of the clear liquid onto the plate, leaving any undissolved salt behind.
- Leave the plate somewhere warm and still for two or three days.
- Look at the crystals that form, with the magnifier if you have one.
What's going on?
As the water evaporates, the sodium and chloride ions have less water to stay dissolved in, and they lock back together into their lattice. Because each ion sits in a cube of neighbours, the crystals grow as cubes, sometimes with stepped, hollow faces.
Safety Ask an adult to help with the warm water. Don't eat the crystals off a plate left out for days.