Why does sugar dissolve faster in hot water compared to cold water? Why does sugar dissolve faster in hot water compared to cold water?
 A: I am going to have to respectfully disagree with Pranjal Rana. 
The reason that sugar dissolves more quickly in hot water than in cold water has to do with the kinetic energy of the particles. 
The faster (hotter) the water molecules are moving, the more energy they give to the sugar molecules when they collide with them. 
Think about it this way: a sugar crystal is just a lot of sugar molecules stuck together. You dissolve the crystal you need to hit the molecules with enough force to break them off of the rest of the crystal. 
A: I will explain it with the help of Le Chatelier principle. It states that the rate of reaction depends on the temperature. If the reaction is exothermic, then decrease of temperature will increase the rate to compensate the effect caused by decrease of temperature. However the rate will decrease if the temperature is increased, so that the equilibrium is again obtained. Similarly it happens with endothermic reactions but inversely. 
I hope I was able to answer your question.
