In today's China, many children who are enjoying nine-year compulsory education are happy. In this increasingly well-educated society, scientific experiments have entered the classroom, and many children have been exposed to science. So what interesting experiments have we done inside and outside the classroom? Let's take you and Bian Xiao to get to know each other.

1. I found that my head sinks when I breaststroke in the swimming pool. The method is to make a cloth cover, put yourself in it, then use sand instead of measuring the volume, then weigh it to get the density, then measure the density of the pool water and compare it with your own density. The result is always so weird that I still can't figure out why. It turns out that I won't sink as long as I lie on my back. This experiment is very interesting, especially in the process, which involves calculation and practice. For every student who is good at discovering and observing, no matter how big or small the problem is, it is of great significance for them to explore once they find something they can't figure out, so that they can grow up in exploration and gain more knowledge in practice.

2. Magic toothpicks, toothpicks in water, will swim with sugar cubes in water or soap in water. Carefully put the toothpick on the water. Put the sugar cubes in the basin, away from the toothpicks. The toothpick will move towards the sugar cube. Change a basin of water, put the toothpick carefully on the water, and now put the soap in the basin. Toothpicks near toothpicks will stay away from soap. The principle is that the cube will absorb some water when placed in the center of the basin, so there will be a small water flow in the direction of the cube, and the toothpick will also move with the water flow. However, when you put soap into the basin, the surface tension at the edge of the basin is strong, so you will pull the toothpick out.

3. Bottle competition. Two bottles with equal weight of sand and water rolled down from a height to see who reached the finish line first. Use a rectangular board and two books to reach a slope, pour water into another bottle, pour sand into the bottle, put the two bottles on the board, and let the two bottles roll down at the same starting height at the same time. Bottles filled with water reach the finish line earlier than those filled with sand. The principle is that the friction between sand and the inner wall of the bottle is much greater than that of water, and there will be friction between sand, so its sliding speed is slower than that of a bottle filled with water.