Silicone sealants and adhesives are synthetic compounds with a wide variety of forms and uses. They are usually heat-resistant and rubber-like. Sealants are viscous materials that change state to become a solid once it is applied. Sealants create a barrier to prevent the penetration of air, gas, dust, fire, smoke, liquid, and even noise from one location into another. Typically, sealants are used to close small openings that are difficult to eliminate through other processes or materials.