explain why part of a pencil that is placed in a glass of water appears bent in relation

The pencil will bend in direction due to the refraction effect of light ,  this is to tell you that light rays rays from the pencil is incident on your eye, and when you remove the pencil from the glass of water, you will observe it did not actually bend, what really happened? Did we apply any force on the pencil?,  no!

Then what actually happened? He light rays coming from part of the pencil immersed in water is in different medium with the part  of the pencil outside the water .

 we know that when light rays move from one medium to another they bend in direction. This is to tell you that refraction of light rays actually has taken place.

 the part of the pencil in water and that outside water are in different medium , the light ray from part of the pencil inside water is what is refracted.