What incident shows that Matilda had a special power?

In theis section, Miss Trunchbull sits down at the teacher's desk and begins to pour herself a glass of water. When the newt that Lavender put in falls out she shrieks and jumps around, then immediately blames Matilda even though the girl insists that she did not do it. Miss Trunchbull continues to shout at her and Matilda gets so angry, and she stares at the glass with the newt in it, feeling some kind of power brewing inside her. She wills the glass to tip over in her mind, and it wobbles, until it finally topples over and the newt spills right onto Miss Trunchbull.