Polybutadiene, used in truck tyres, is a polymer of buta-1,3-diene. The spatial arrangement of atoms in the polymer depends on the type of catalyst used.

Any two of:
heterogeneous catalyst is in different phase than reactants AND homogeneous catalyst in same phase $✔$

homogeneous catalysts chemically change/react and reformed at end of reaction
OR
reactants adsorb onto heterogenous catalyst and products desorb $✔$

heterogeneous catalysts are more easily removed than homogenous catalysts $✔$

heterogeneous catalysts can function at higher temperatures $✔$

homogeneous catalysts are «generally» more selective $✔$

homogeneous catalysts offer a broader range of reactions $✔$

**Note:**Accept “state” for “phase”.

Accept “heterogeneous catalyst provides a surface to activate reaction”.

elastomers bend under force «and return to original form when force is released»
OR
elastomers make tyre more flexible $✔$

allows greater contact with road $✔$

does not contain heterocyclic ring with 2 oxygen atoms
OR
middle ring has only 1 oxygen atom $✔$

produces similar toxic effects to dioxins $✔$