Final answer:
The ball with arrows pointing away is a negatively charged particle, the ball with arrows pointing inward is a positively charged molecule, the grey ball represents an uncharged molecule, and it is the one that will not move when placed in an electric field.
Step-by-step explanation:
The question relates to the behavior of charged particles and how they interact with electric fields, which is part of high school physics. The student is given descriptions of three differentiated balls in boxes with arrows showing the direction of force in an electric field and is asked to identify which ball represents a negatively charged particle, a positively charged molecule, and an uncharged molecule, and which will not move when in an electric field.
The ball with arrows pointing towards it represents the positively charged molecule because electric field lines point toward negative charges and away from positive charges. The ball with arrows pointing away represents the negatively charged particle, as field lines point away from a positive charge. The grey ball, without any arrows, represents an uncharged molecule as it exhibits no interaction with the electric field.
In the presence of an electric field, only the uncharged particle will not move; charged particles will experience a force and move according to whether they are positively or negatively charged.