ゼラチンは、冷えると固まる性質があります。

、。

Gelatin has the property of solidifying when cooled.

Literal

Gelatin [topic-は], cool-[when-と] harden property [subject-が] exists.

ゼラチン is the katakana rendering of 'gelatin.' 冷えると固まる 'solidifies when cooled' uses the ~と conditional for a natural, repeatable phenomenon. 性質 'property, characteristic, nature' is the standard word for describing material properties in scientific contexts.