1.
In chemistry, a ~ substance or a substance with ~ properties is a substance which increases the speed of a chemical reaction.
...carbon molecules with unusual chemical and ~ properties.
ADJ: ADJ n
2.
If you describe a person or thing as having a ~ effect, you mean that they cause things to happen or they increase the speed at which things happen. (FORMAL)
Governments do, however, have a vital ~ role in orchestrating rescue operations.
ADJ: usu ADJ n