2)Soap and pepper experiment:
•Fill a shallow dinner plate with enough water to just cover the bottom of the plate.
•Add the black pepper on the water with a suitable amount so that you can see it.
•The water will get turbid and not clear like what you see in the figure.
•Touch the water with a clean wooden stick or a toothpick, you will recognize that nothing take place(no changes at all).
•Add some detergent or dish soap to the toothstick and dip it to the bottom of he plate again. This time, the pepper scatters away toward the edges of the plate in every direction.
Scientific explanation:
•In fact, the pepper isn’t the real cause behind the motion you saw in the picture and the video, but it is only used to deliver a good vision for what is going to take place. You can use anything that floats instead of the black pepper. The real reason behind this motion is the detergent that reduces the water's surface tension.
•Surface tension exists due to