What type of reaction involves the removal of water from molecules to join these molecules together?

The type of reaction that involves the removal of water from molecules to join these molecules together is called a Dehydration Synthesis or Condensation Reaction.

Here are the steps of this reaction:

1. Two or more molecules approach each other, with each molecule having a hydrogen atom and the other having a hydroxyl group (-OH).
2. The hydrogen atom and the hydroxyl group interact and form a water molecule (H2O), which is then removed.
3. The removal of the water molecule allows the two original molecules to join together, forming a new, larger molecule.
4. This process can be repeated to form long chains of molecules, or polymers.

This type of reaction is common in the formation of many biological polymers such as proteins and carbohydrates.