What causes static electricity to build up?

Static electricity builds up primarily due to the buildup of a stationary charge caused by physical contact and movement of objects. This phenomenon, known as triboelectric charging, occurs when two different materials come into contact and then are separated. Electrons can be transferred from one material to another during this process, leading to an imbalance of electric charge.

For instance, when you rub a balloon on your hair, electrons are transferred from your hair to the balloon. As a result, the balloon becomes negatively charged, while your hair loses electrons and becomes positively charged. This leads to an accumulation of static electricity that can cause the balloon to stick to surfaces or create sparks when close to other objects.

The other options do not accurately describe the process through which static electricity accumulates. Temperature changes might affect the distribution of charge in certain contexts, but they are not a primary cause of static buildup. Electrical discharges, such as those from high voltage lines, result from existing electrical imbalances rather than causing the buildup of static electricity itself. Lastly, chemical reactions may produce electric charge in specific conditions, but they are not directly related to the general phenomenon of static electricity that's typically observed in everyday life.