catalyst

Everyday

1. (science) A substance that makes a chemical reaction go faster without being used up itself. tree →
2. A person or event that makes a big change happen, or makes it happen sooner. tree →

In the lessons

In science lessons it is the substance that speeds up a reaction, like enzymes in your body that help digest food, or the catalytic converter in a car. In history and stories it is the event that sets off big changes — «the catalyst for the war». It tells the reader that something started or sped up a change. Phrases: «a catalyst for change», «acted as a catalyst».

Examples

• Enzymes in your saliva act as catalysts to break down food. tree →
• A catalyst speeds up a reaction but is not used up. tree →
• In the experiment, the catalyst made the hydrogen peroxide fizz quickly. tree →
• The new teacher was a catalyst for change in our school. tree →
• The storm was the catalyst that made the town build a stronger sea wall. tree →
• Rosa Parks's brave act became a catalyst for the bus boycott. tree →
• Platinum is a catalyst in a car's exhaust system. tree →

Note

Countable: a catalyst, catalysts. Say «KAT-uh-list». Adjective: catalytic (a catalytic converter). In science the key point: the catalyst is still there, unchanged, at the end of the reaction.