How to predict whether it will rain or sunny?

Find an old doll and be our "weatherman". Make a bow for the doll with a piece of soft paper, soak the bow in the solution of cobalt dichloride (a chemical, available in chemical stores), take it out to dry, and put a bow on the doll. This specially treated bow can show the humidity of the air.

If the air is humid, the bow will appear pink; If the air is dry, the bow will appear blue. It can be predicted whether it will be sunny or rainy. There is a simpler way: find some pink crepe paper to make flowers and green crepe paper to make leaves, and you can make a beautiful flower.

Soak a cup of strong salt water and find a clean brush to wet the petals with salt water. After drying, put this bunch of flowers in a vase. When talking about the color of flowers, it means that the weather is fine; When the color darkens, the weather turns from sunny to rainy.

What did you find?

If the color of the flowers fades, the weather must be sunny; If the color of the flowers darkens, it will be cloudy or rainy.

Secret principle:

This is because paper flowers soaked in concentrated salt water absorb water easily. The cloudy weather is low and the humidity in the air is high. As soon as the paper flower comes into contact with high humidity air, it can absorb the moisture in the air, so the paper flower looks darker. On the contrary, on sunny days, the air pressure is high and no moisture can be absorbed. Of course, the paper flower is the original color.