Step 1: Understand the task.
We must find the pair where the substance does not match the property written beside it. We check each property one by one against known chemistry.
Step 2: Check silica.
Silica $SiO_2$ has a giant covalent network in which every silicon and oxygen is strongly bonded. Breaking such a structure needs a lot of energy, so it truly has a high melting point. This pair is correct.
Step 3: Check stannous chloride.
Stannous chloride is $SnCl_2$, where tin is in the $+2$ state. Tin easily moves up to the more stable $+4$ state by losing electrons, so $SnCl_2$ acts as a reducing agent, not an oxidizing agent. This pair is wrong.
Step 4: Check silicones.
Silicones are polymers with silicon and oxygen chains and organic side groups. They repel water and resist heat, so this pair is correct.
Step 5: Check zeolites.
Zeolites are porous aluminosilicates that swap their ions with ions in solution, so they act as ion-exchangers. This pair is correct.
Step 6: Pick the mismatched pair.
Only the stannous chloride pair is wrong, since $SnCl_2$ is a reducing agent rather than a good oxidizing agent.
\[ \boxed{\text{Stannous chloride - good oxidizing agent}} \]