We have just finished up our weather unit. Most of this unit was posters, worksheets, and watching little movies. There were a handful of good experiments which our curriculum suggested. One of them we did was on different kinds of participation. For sleet, we crumbled up little pieces of paper. For snowflakes, we had little one inch square pieces of paper.
The girls threw both the sleet and snow in the air at the same time. Every single time the sleet landed on the floor first and the snow flakes floated down.
Also on the video, there is a flag in front of the house. It starts out stationery during "calm" and eventually gets blown away by the "hurricane" level wind. Several days after we did that lesson, the girls found a flag in our garage. Catherine held it still and told me "this is calm."