Sprinkle some salt and ground pepper onto a plate. Blow up a balloon and rub it against your dry hair. Now slowly bring the balloon close to the salt and pepper. The pepper will leap up and stick to the balloon.
When you rub the balloon, it picks up electrons from your hair and becomes negatively charged. The electric charge of the balloon attracts light and fluffy particles like pepper. The charge pushes electrons toward the back of each pepper particle and then attracts the front side, which now has a positive charge. That doesn't work as well on salt grains. Their electrons don't push away as easily, and the grains are heavier.
Photo by Nannette Bedway