Adhesion
Adhesion is the force that makes tape stick to a surface.
Honey drips down the side of a glass jar and clings to it. The honey molecules are pulled toward the glass and hold on tight. This pull between two different materials is adhesion. Tape works the same way — its sticky layer bonds to whatever surface it touches.
Explaining adhesion by grade level
Press tape onto a smooth steel plate. It grips tight. Now press the same tape onto a rough, bumpy wall. It peels right off. The tape holds better on some surfaces than others. That grip between the tape and the surface is adhesion.
Projects that explore adhesion
You can measure adhesion by tying a string to tape and adding washers one by one. The more washers it holds before letting go, the stronger the stick.
Not all tapes stick the same way. By pulling five types of tape off a steel plate, you can compare how much weight each one holds. Duct tape holds the most, while some thin tapes let go much faster.