Hello and welcome to your chemistry in your cupboard. I'm Catherine and I'm an
education coordinator for the Royal Society of Chemistry. Today I'm going to
try some space craft survival. I'm going to investigate how to get clean water
from contaminated water. For example if astronauts need to purify
their water to survive in space. You can try this at home with a responsible
adult. Let's get started. For this experiment we're going to need one big
container and a small one that fits inside. If you're using something
lightweight you'll also need some blue tack to hold it in place. Some water, just
cold tap water is fine, and a teaspoon. Something to make the water dirty, we'll
call this our contaminant as it contaminates the water. I'm going to use
some salt and some blue food colouring, but you could also use powder paint.
Some cling film and something to weigh the cling film down, this could be a ball
of blue tack, a stone, or I've got a little pot. And some time as this
is an experiment we can observe over about a week. First I'm going to make my
contaminated water by mixing some tap water with some blue food coloring and
some salt. And give that a good mix until it's all dissolved.
Now let's set up the containers. So put the smaller one in the middle of the
larger one. Mine's already quite heavy but if you're using something made of
plastic you'll need to stick it to the bottom with some blue tack. Then I can
pour my water into the larger container, making sure it doesn't spill into the
smaller container in the middle. The more water you use the longer the experiment
will take. Then cover the whole thing with cling film. It doesn't need to be
stretched too tight as long as it covers all the edges. And then finally
pop a weight on the top. The water will evaporate and then collect under the
cling film, and then run down until it gets to the weight in the middle, and
drop into the smaller container, so make sure everything is lined up properly.
Next we wait. Pop the experiment in a sunny place,
maybe a window sill, and see what happens over time.
So we left the experiment running for about a week and while it was running
you could see condensation on the inside of the container, and little droplets of
liquid on the cling film running down into the middle. I've let it cool down so
there's no more liquid on the cling film. So let's see what's happened. So I can
see that most of the liquid that was in the outer container has evaporated and
it's left behind little blue crystals. So that must be the salt that I dissolved in
the water with the blue food colouring. In the bowl in the middle I've got some
clear liquid, but let's have a look properly. Wow,
that looks pretty clear to me. It doesn't smell of anything and it tastes like
pure water too. But if you've used non-food contaminants
don't try the liquid afterwards. So what we've done is we've cleaned our water
using the water cycle. So in our mixture the water, with the heat from the sun,
evaporated, and then it condensed. In the water cycle it does this in the
clouds but in our experiment this was on the cling film. And then it precipitates
or rains back down to earth and in our experiment this was the water dropping
from the cling film into the container in the middle. So that was spacecraft
survival. If astronauts in space needed to purify their water this might be one
way they'd do it. I wonder what other contaminants you could remove using this
method? Could you separate squash from water? Have a go and let us know how you
get on using the hashtag chemistry in your cupboard. We'll be back with more
experiments soon. In the meantime make sure your grown-up subscribes to the
youtube channel for all the latest chemistry in your cupboard videos. See you soon.