Washing up is less of a chore when done with hot water because heat melts fats. Heating fat makes its molecules vibrate faster and faster, weakening their bonds so that they are only loosely attached and behave like a liquid rather than a solid.
Fats have fairly low melting points so a hot tap is usually enough to make them runny so they can be washed away. Bacon fat, for example, is solid at room temperature but melts at around 40 degrees Celsius (104 degrees Fahrenheit).
Adding a few drops of washing- up liquid to disperse grease makes the process even more effective.
Answered by Alexandra Cheung