19) Rice Krispies are very lightweight and electrically neutral. If a negatively charged rod is placed in with the puffs. they will be attracted to the rod. However, after a short period of time they fly off in all directions. Why does this happen? [2 marks]

The Rice Krispies are initially attracted to the negatively charged rod due to **polarization**. The negative charge on the rod repels the electrons in the Rice Krispies, causing a slight positive charge to develop on the side of the Krispies closest to the rod. This induced positive charge is attracted to the negative rod.<br /><br />However, once the Rice Krispies touch the rod, some of the excess electrons on the rod transfer to the Krispies, giving them a net negative charge. Since like charges repel, the now negatively charged Rice Krispies are repelled away from the similarly negatively charged rod, causing them to fly off.<br />