What makes jello melt quickly?

Temperature

The higher the temperature, the faster Jell-O will melt. This is because heat causes the gelatin molecules in Jell-O to break down, which reduces the thickness of the dessert.

Mixing

Stirring or shaking Jell-O causes the formation of air bubbles, which can weaken the bonds between the gelatin molecules.

Acids

Adding citrus acids such as lemon juice and vinegar reduces the gelling strength. This weakens the gelatin network, causing the jelly to lose structure.