British Sign Language Glossaries of Curriculum Terms

BSL Chemistry Glossary - catalyst - Definition

I'm going to explain to you what a catalyst is and what it's used for. Sometimes a chemical reaction can take place very slowly but you might want to speed things up, especially in an industry, where they may need things more quickly. To do this we can add a catalyst like the one I have here. When I mix in the catalyst it will speed up the rate of the reaction, a new product will be formed (at the end of the reaction) but the catalyst will still be present. Let me show you a nice example of this. I'm going to put a catalyst into one of the glass cylinders I have here and we'll see which reaction is faster. I'm going to make ‘Elephant's Toothpaste!' Let's see what happens ...

I'm just going to put the catalyst in one of them, so again, watch what happens. One of them reacted much more quickly, but the other one hasn't really got going and we'd have to wait probably until tomorrow for the reaction to have taken place, whereas the other one happened just now.

Let me explain to you what was going on there and what is it that's been produced. Both of these glass cylinders contain H₂O₂ (hydrogen peroxide) which naturally breaks down into water and oxygen, but this process takes a long time. Adding the catalyst (from the jar) speeds this process up. I added the washing up liquid because it forms bubbles from the oxygen that's released and that's why we get this foaming. The yellow colouring in the jar is from the food colouring that we added (which is the same colouring that we put in cakes). We can also see the black colour of the catalyst which means that it hasn't changed, it's still exactly the same and we could use it again - manganese dioxide. There are many different types of catalyst and these can be used in a number of different reactions.