How to predict the weather with a flower?

This is a scientific experiment in a primary school. It is not accurate to guess the weather, but only a rough understanding of air humidity.

Make sunny and rainy flowers that can quickly predict the weather.

Experimental supplies:

Filter paper, beaker, glass rod, alcohol lamp, cobalt chloride crystal.

Method:

Take a piece of filter paper, soak it in saturated solution of cobalt dichloride repeatedly, dry it until it is pink, then cut it into petals, and tie the cut petals into a flower with thin thread or iron wire.

Experimental principle:

When the weather is clear, there is little water in the air, and cobalt dichloride is difficult to absorb water, so it is blue; Before the rain, the water in the air increased, and the yuhua district absorbed a small part of the water, and part of the cobalt dichloride dissolved the cobalt complex. At this time, the blue and red colors mixed to appear purple; When it rains, the moisture in the air increases sharply, making all the cobalt dichloride in the flowers become cobalt complexes, which are pink.