Fill a shoebox lid with flour and, using a ruler, level it off so that the flour is even. When it starts raining, place the shoebox lid outside until 15 to 25 raindrops have fallen into the flour. Bring the box inside and look at the raindrops. Then, using a sieve, carefully pour the flour into a sieve over a bowl to sift it. The lumps of flour that remain in the sieve are preserved raindrops that you can look at and measure.
Fill a glass full of water. Place a table near a window where the sun is shining through, and place the glass on the edge of the table in the sunlight, so it is half on the table and half off. Ensure that the glass does not fall off the table. Place a white sheet of paper on the floor and adjust the glass of water and paper until you can see a "rainbow" on the paper. Light is made up of lots of colors, and when it passes through water, it is broken up into all of those individual colors.
Put a little water in a small paper cup, place it inside a baggie and close the baggie. Tape it to a window, ensuring that the water doesn't spill. Leave it for a few hours. The water inside the cup will evaporate and droplets will gather on the inside of the bag and then drip down to the bottom of the bag. This illustrates the water cycle, during which water evaporates from lakes and rivers, is collected by clouds and then falls again as rain.
Fill two small metal cans one-quarter of the way full with water. Stir 4 tablespoons of salt into the water in one can, then fill both cans with crushed ice. Wait for a few minutes. Dew will form on the outside of the can without the salt, and frost will form on the can with the salt. This is because the salt makes the water and ice mixture colder so that the condensation on the outside of the can freezes into frost instead of staying as dew.