Fun with Pepper

I've got two entirely different concepts that are illustrate by these two activities.

Activity One: Magic Pepper

Give students a mixture of salt and pepper. Perhaps a 1/4 to 1/2 teaspoon on a paper towel or desktop.

Give students a plastic spoon and a piece of wool. Have them rub the spoon on the wool to create a charge.

Allow students to hold the charged spoon over the salt and pepper.

• Note the pepper rises more easily due to it being lighter.
• Both salt and pepper will be attracted to the charged spoon. Salt is ionic. The pepper has polar covalent qualities.

You can whisk the leftover salt and pepper on the floor and the custodian shouldn't notice or be tidy and carry the rubbish bin around the classroom and whisk what is not used in.

Activity Two

Mix pepper in water. You will notice that the pepper floats. This is because pepper is not soluble in water. Take a toothpick, dip it in dishwashing detergent. Touch the soap laden toothpick on the surface. Observe what happens.

The explanation I have heard is this occurs because the dishwashing liquid reduces the cohesion between water molecules and this causes the pepper to move.

I suspect that the dishwashing liquid creates an emulsion and disperses the pepper. Sound in your thoughts please.