Tube Shaped

How could you show that the colourless liquid in the u-shaped tube is water?

Zoe and Emil do an experiment o find the products of combustion of a candle.
when they start the pump, air is sucked through the apparatus.
when the candle is alight they soon see:
a colourless liquid collects in the u-shaped
the colourless lime-water goes cloudy.
how could you show the colourless liquid collected in the u-shaped tube is water?

Stick some anhydrous copper sulphate (CuSO4) in the u-shaped tube (a grey powder)

If water is present, copper sulphate (CuSO4·5H2O) will form (a distinctive blue coloured crystal)

5th東方M-1ぐらんぷり: Spin Kappa (English Subtitles)